ICW Technical Doc by i-c-w33

Version 2.0

Technical Manual

Contents

Introduction 1.0 Introduction 1.1 Suitability of Materials and Workmanship 1.2 Guidance for Innovative Designs and Construction Methods

Substructure 06 11 13

Inspections 2.0 Introduction 2.1 Site and Construction Overview 2.2 Excavations 2.3 Foundations to Ground Floor 2.4 Ground Floor to Upper Floor 2.5 Upper Floor to Roof Structure 2.6 Pre Plaster and Plaster Board 2.7 Completion

14 15 19 20 22 26 27 33

Site Investigation 3.0 Site Investigation

Foundations 4.0 Foundations 4.1 Strip and Trench Foundations 4.2 Minimum Depth of Strip Foundations 4.3 Concrete Mix 4.4 Stepped Foundations 4.5 Engineered Foundations 4.6 Engineered Fill 4.7 Piled Foundations 4.8 Raft Foundation 4.9 Foundations and Trees 4.10 Construction Principles

42 43 44 45 47 48 48 49 50 51 53

5.0 Substructure 5.1 Walls below DPC 5.2 DPC 5.3 Service Penetrations 5.4 Pipes Bedded into Walls 5.5 Pipes Lintelled through Walls 5.6 Waterproofing Design 5.7 Types of Waterproofing

54 55 56 57 57 58 59 60

Drainage 6.0 Drainage 6.1 Excavation 6.2 Access 6.3 Connection 6.4 Gullies 6.5 Bedding Material 6.6 Backfill 6.7 Flexible Pipes 6.8 Drainage System 6.9 Above Ground Drainage 6.10 Drainage Layout 6.11 Ventilation 6.12 Testing

62 63 64 66 66 67 67 68 69 70 71 72 73

Ground Floor 7.0 Ground Floor 7.1 Ground Bearing Slab 7.2 Precast Beam and Block Floors 7.3 Suspended Timber Floors 7.4 Damp Proof Membrane 7.5 Radon Gas Barrier

74 75 76 77 78 79

Superstructure 8.0 Superstructure 8.1 Exposure 8.2 Bricks 8.3 Blocks 8.4 Masonry Protection 8.5 Mortar 8.6 General Advice on Cavity Wall 8.7 Solid Walls 8.8 Cavity Walls 8.9 Framed Walls 8.10 Lateral Restraint 8.11 Lateral Restraint Straps 8.12 Wall Ties 8.13 Cavity Closers 8.14 Movement Joints 8.15 Structural Openings 8.16 Cavity Trays & DPC 8.17 Floor Joists 8.18 Notching & Drilling 8.19 Floor Decking 8.20 Particle Boarding 8.21 Staircases 8.22 Internal Walls 8.23 Fire Resistance 8.24 Sound Insulation 8.25 Pre Completion Testing 8.26 Robust Details 8.27 Chimneys

Cladding 80 81 82 82 83 84 84 85 86 87 88 89 89 90 91 92 93 94 95 97 97 98 99 101 102 103 103 104

9.0 Introduction 9.1 Timber Boarding 9.2 Timber 9.3 Plywood 9.4 Render on to Boarding 9.5 Tile and Slate Cladding 9.6 Other Cladding 9.7 Weather Resistance of Walls and Cladding 9.8 External Treatment 9.9 Internal Treatment 9.10 Interstitial Condensation 9.11 Surface Condensation 9.12 Control of Moisture Penetration 9.13 Thermal Insulation of Walls and Claddings 9.14 Render Application 9.15 Finishes 9.16 Further Guidance

106 107 110 111 111 112 113 113 114 114 115 115 116 117 118 119 120

Conversion

Roofs 10.0 Roofs 10.1 Bracing & Lateral Restraint 10.2 Fire Stopping 10.3 Roof Coverings

122 123 125 126

Timber Frame 11.0 Timber Frame 11.1 Introduction 11.2 Substructure 11.3 Sole Plate 11.4 Sheathing Boards 11.5 Fixing 11.6 Breather Membrane 11.7 Fire Stopping 11.8 Internal

130 131 132 132 133 134 135 136 137

Modern Methods of Construction 12.0 Modern Methods of Construction

138

Internal Services 13.0 Internal Services 13.1 Space Heating 13.2 Escape Window 13.3 Safety Glazing

140 144 146 147

14.0 Inspection Process 14.1 Site and Construction Overview 14.2 Foundation to Ground Floor 14.3 Strip Out and Assessment of Original Structure 14.4 Superstructure to Upper Floor 14.5 Upper Floor to Pre Plaster including Roof Structure 14.6 Completion

148 149 153 155 157 161 168

Conversion Guidance 15.0 Introduction 15.1 Assessment Process 15.2 Substructure 15.3 Superstructure

174 176 177 184

Introduction

1.0 Introduction To satisfy the requirements of this manual you must comply with: •

The applicable technical Building Regulation requirements which will be dependent upon the location within the United Kingdom (i.e. England and Wales, Scotland and Northern Ireland) and the relevant transitional technical bulletins and updates.

•

All other statutory technical requirements e.g. Water Regulations, the Gas (Installation and Use) Regulations, etc.

•

Building Regulation requirements are described in functional terms (in italic text) and reference is made to any corresponding regulation in England & Wales, Scotland and Northern Ireland. Where a Building Regulation requirement is not currently applicable in a country, it shall be treated as an International Construction Warranties Limited requirement. In determining whether compliance with the Requirements has been achieved: •

It is for the building control body (Local Authority or Approved Inspector) to satisfy themselves on the compliance of plans and work with the Building Regulations. It should be noted that where a dispute arises, International Construction Warranties Limited has the right to delay the issuing of the Insurance Certificate until settled.

•

For the avoidance of doubt, when several standards are referred to, the higher standard shall apply unless previously agreed in writing by the International Construction Warranties Limited Technical Department.

•

The decision of International Construction Warranties Limited shall be final determining these Requirements.

The additional requirements set by International Construction Warranties Limited.

When interpreting the Requirements and Guidance the standards of construction achieved shall never fall below the minimum standard set by the controlling Building Regulations.

Requirements This Technical Manual is divided into several sections corresponding to the various areas of construction. The International Construction Warranties Limited requirements and other statutory constructional requirements are shaded for ease of identification. These Requirements are in addition to compliance with Building Regulations and for the avoidance of doubt compliance with the Requirements is mandatory. All dwellings, covered by a warranty from International Construction Warranties Limited, shall comply with the Requirements in force at the time that documents for the dwelling were deposited with the relevant authority for the purposes of the Building Regulations. The pages following the Requirements provide guidance on showing compliance. For the purpose of this Manual, the term Building Regulation refers to the equivalent or corresponding statute in the various countries covered by this manual, i.e. England & Wales, Scotland, Northern Ireland. Where a Building Regulation requirement is not currently applicable in a country, it shall be treated as an International Construction Warranties Limited requirement.

1.0 International Construction Warranties Limited Requirements

The Construction shall comply with the Building Regulations. Paths and drives shall be laid to falls and be adequately drained. Site fill and consolidation of subsoil under paths, outbuilding, etc. Shall be carried out using non-organic materials and achieve an appropriate level of compaction suitable for the final finish. Where on-site sewage treatment and disposal systems and/or soakaways are proposed, a porosity test shall be carried out to ensure that the ground conditions are suitable for that form of drainage discharge. Subsoil drainage shall be provided within the vicinity of outbuildings, hardstandings, paths, drives and the like if the ground is liable to waterlogging or if the presence of a water table is likely to affect the stability of the ground. Subsoil drainage shall be provided in garden areas if the ground is liable to constant waterlogging with 4 metres of the dwelling. Garden areas shall be laid to levels and gradients appropriate to the levels of the buildings, adjacent highways and services. An adequate method of rainwater disposal shall be provided to all permanent outbuildings: External doors and windows shall be designed and constructed to: •

Provide an adequate deterrent to forced entry into a dwelling.

•

Be weather-tight.

•

Shed water from the building in an effective manner.

•

Be provided with a draught strip.

The enveloping walls and floors of a dwelling, including jambs, sills and heads of door and window frames, shall be designed and constructed so as to: •

Prevent the build-up of excessive condensation within the fabric of the construction.

•

Prevent cold bridges causing local surface condensation to occur, and prevent the excess flow of air into a dwelling.

The width of internal stairways shall be such as to offer safe passage to users of the building. The following accommodation and amenities shall be provided to a dwelling:

•

Adequate whole house heating and domestic hot water supply.

•

Electrical installation with an adequate number of lighting points and socket outlets, signed off on completion with an Electrical test certificate.

•

Gas supply to kitchen cooker position (where a mains supply passes adjacent to the dwelling), signed off with a Gas Safe certificate.

•

Adequate storage space at each floor level.

1.0 International Construction Warranties Limited Requirements

Building service installations shall be designed and constructed so that they: •

Operate in a safe manner.

•

Are provided with adequate controls to allow their operation, isolation and drainage.

•

Are provided with adequate means of access where necessary for the purposes of adequate inspection, maintenance and replacement.

All service installations requiring periodic attention by the user shall be provided with adequate operating and maintenance instructions. Finishes to walls, floors, fixtures and ceilings in conjunction with levelling and supporting surfaces should provide adequate resistance to impact, wear, water, and light chemical attack, due account being taken of the location of the element. In addition, externally located finishes should have resistance to frost and ultra-violet radiation. Decorative elements shall be completed to adequate basic levels of visual quality (higher standards which may be agreed between the builder/developer and the purchaser are not included in this Requirement) Adequate vehicular and/or pedestrian access shall be provided: •

From an adjacent street, to an entrance of the dwelling and to any garage or other parking area within the curtilage of the site.

•

From the dwelling to any garage and outhouse.

Detached garages and outbuildings shall be: •

Structurally stable and withstand movement of the subsoil, due account being taken of the ground conditions and wind exposure for the site.

•

Reasonably restraint to rain and ground water.

Retaining walls and garden walls shall be stable, withstand movement of the subsoil and be adequately protected from the adverse effects of ground moisture and freezing. In addition, retaining walls shall be constructed so as not to allow the build-up of ground water. All external ramps and steps providing access to a dwelling shall be safe to use. Garden areas shall be reasonably cleared of builders materials prior to handover. Accuracy, quality of finish and protection: •

Any element covered by another element shall be finished to adequate standards in order to properly receive the covering element and be adequately protected prior to being covered up.

•

Any element not covered up by another element shall be provided to an adequate basic standard of visual finish and protected prior to handover, (higher standards which may be agreed between the builder/developer and the purchaser are not included in this Requirement). 8

1.0 International Construction Warranties Limited Requirements

Design and construction: •

Adequate investigations shall be carried out to identify design data which vary from site to site. Total and differential movement of an element shall be adequately limited or accommodated, such that damage does not occur to itself or to other elements.

•

Methods of fixing, jointing, bonding, supporting, tying together, surface preparation and sealing of elements shall be adequate, due account being taken of the location and anticipated life of the element.

•

The design and construction of any element and choice of materials shall be such that a reasonable level of safety to persons is provided.

•

The method of achieving compliance with any Requirement shall not result in the failure to comply with another Requirement.

•

Any element which performs the role of more than one element shall comply with the Requirements applicable to each element.

•

Every dwelling shall be cleared of builders materials and debris and adequately cleaned prior to handover.

Durability – Materials and workmanship: •

All materials, except for decorative materials, shall have a minimum life span of not less than 30 years for items affecting structural stability and 10 years for non-structural items, due account being taken of their intended location and use.

•

Materials shall be adequately treated to prevent their premature decay or decomposition and adjacent materials shall be compatible with each other.

•

Materials shall be stored, protected and properly treated prior to being incorporated into the dwelling.

•

The requirements shall be met whilst the building is in service.

Where deemed necessary the developer/builder should commission a comprehensive survey and report by an Expert for the structure of the building or elements of structure, to indicate the condition and lifespan of those elements. Provision of integral damp-proof course and damp-proof membrane to provide an effective barrier against rising damp. Any damp proofing products must have an insurance backed guarantee acceptable to International Construction Warranties Limited otherwise these works will be excluded from cover. Where alterations, repairs or replacement of flat roof coverings are part of the works during a conversion, these works must also have an insurance backed guarantee acceptable to International Construction Warranties Limited otherwise these works will be excluded from cover. Independent inspection and treatment of timbers against fungal and insect attack, where necessary, together with replacement of all rotting timbers and associated work necessary to remedy the cause of dampness. Timber treatment to include an insurance backed guarantee, acceptable to International Construction Warranties Limited. Historic buildings shall achieve as reasonable, as is practicable level of sound insulation. The results of the “test and declare” testing shall be displayed in the building.

1.0 Other Statutory Requirements

All elements of construction covered by this Manual shall comply with any relevant statutory requirements. Services passing through the building envelope shall comply with the requirements of the relevant Gas, Water, Electricity and Drainage Authorities. The protection of building services supplies and installations in waterlogged ground shall satisfy the requirements of the Supply Authority. The method of on-site sewage treatment and disposal shall comply with the requirements of the Sewage / Water Authority / Environment Agency. The method of discharge of a private drain or sewer into a public sewer shall comply with the requirements of the Sewage Authority / Environment Agency. The ventilation of voids under ground floor slabs shall be to the satisfaction of the local Gas Authority. Every dwelling shall be provided with a wholesome supply of drinking water to the satisfaction of the Water Authority. Heating appliances shall comply with the requirements of the Local Authority with regard to the Clean Air Acts (smokeless zone requirements). The location of services within the finishes shall comply with the requirements of the Gas, Water, Electricity and Drainage Authorities.

1.1 Suitability of Materials and Workmanship Establishing Fitness of Materials and Workmanship

Product Certification Schemes

The following methods exist for establishing the fitness and assuring the quality of materials and workmanship.

Product certification schemes operated by independent assessment organisations exist for assuring the conformity of a product to a specific standard, e.g. The Kitemark Scheme operated by the British Standards Institution.

Construction Products Directive The CE mark is a claim that a product, when properly used, enables the construction works in which it is incorporated to meet the relevant essential Requirements of the EC Construction Products Directive; the claim is normally based on compliance with a harmonised European Standard or European Technical Approval. The essential Requirements encompass:

Quality Assurance Schemes Various quality assurance certification schemes exist for design, construction and product manufacture. Firms registered under such schemes are considered to have the capability to provide or perform to a consistent level of quality within a defined scope of registration. Quality Assurance schemes registered by the United Kingdom Accreditation Service (UKAS) provide assurance as to the integrity of such schemes. Quality Assurance schemes do not, however, certify conformity with a particular product or service standard, or that the standard is adequate for a specific application.

•

Mechanical resistance and stability.

•

Safety in case of fire.

•

Hygiene, health and environment.

•

Safety in use.

Agrément Certificates

•

Protection against noise.

•

Energy economy and heat retention.

Agrément Certificates issued by the British Board of Agrément (BBA) provide independent certification of the adequacy of a particular product, for a specific use, in cases where a British Standard does not currently exist.

Past Experience Past experience may show that a material is suitable for its intended use or that a method of workmanship is adequate for a particular type of construction.

As with national standards, different classes of performance may be permitted in order to suit varying situations such as climate and required levels of protection. Therefore, products should be carefully selected to ensure that they are fit for their intended purpose. For guidance on material and installation techniques please refer to: http://www.bbacerts.co.uk/publications/literature/

British Standards or European Standards Compliance with a British Standard or an equivalent European standard generally assures the adequacy of a design, method of construction or product where appropriate for a specific use.

Test and Calculations Calculations and destructive or non-destructive tests can show that a design, construction and/or product is adequate for a specific purpose. The NAMAS Accreditation Scheme for Testing Laboratories provides means of ensuring that tests are conducted in accordance with nationally accepted criteria.

1.1

Tests for Reclaimed Materials Reclaimed materials must be subject to a third-party test to show suitability (unless specifically seen and accepted on site by International Construction Warranties Limited prior to incorporation of the particular material in the construction).

Expert Where the appointment of an expert is recommended, the person to be appointed should possess the qualifications, experience and professional indemnity insurance appropriate for the type and complexity of work to be undertaken. Suitable Experts normally include: •

Registered Architects.

•

Chartered Civil and Structural Engineers.

•

Chartered Building Surveyors.

•

Members of the Chartered Institutes of Building (MCIOB).

•

Members of the Royal Chartered Institute of Surveyors (MRICS).

• •

a better standard than set out in the Building Regulations, International Construction Warranties Limited will support the technical manual with additional technical information through data sheets and electronic documents, it is the responsibility of the developer to request this additional information if required.

Workmanship All work on site should comply with the following standards and requirements: BS 8000-0: 2014 Workmanship on construction sites. Introduction and general principles and Regulation 7: Materials and Workmanship of the Building Regulations 2010, 2013 edition, which covers the current European regulation 305/2011/EU-CPR. It is the responsibility of the person carrying out the work to ensure that all work and operations are undertaken by a competent person that is suitably qualified as required. It is the responsibility of the persons carrying out the work to ensure that the following actions are implemented as good practice. 1.

That the materials, products and the completed work are to the required standard and are fit for purpose.

Chartered association of Building Engineer’s (MCABE).

That precautions are implemented to ensure that damage is prevented.

UKAS and ANC members.

That materials are suitably loaded and un-loaded.

That materials are correctly stored and protected from damage and theft.

Health and Safety

That correct installation methods are used.

At all times the site and surrounding area must be safe for site personnel and members of the public and should comply with all relevant health and safety legislation and regulations.

That consideration is given to seasonal variations in weather, to protect against excessive heating, cooling, wetting and drying of construction materials.

That unforeseen problems are reported immediately.

That all work will comply with the relevant standards.

That damaged materials are not used within the project.

Good Practice The warranty manual provides the basic guide on what is required for a developer to reasonably carry out building work on site. It also refers that the basic requirement of the Building Regulations should always be met. As the warranty will be carried out to

10. That all work is completed to a high standard and is fit for purpose. 12

1.2 Guidance for Design and Construction Methods In general, designs and construction methods which cannot be shown to meet the requirements by any of the methods set out in this manual must be approved in advance by International Construction Warranties Limited in writing, generally before commencement on site.

Structural elements should not be cut, drilled or notched on site, except in accordance with the recommendations set out in this manual. Manufactured structural components should not be modified without the express permission of the designer and manufacturer.

All structural elements should be designed by an Expert when not in accordance with either:

If a structural element supports heavy service loads, e.g. a cold water tank, it should be specifically designed for this purpose.

•

Approved Document A (England and Wales).

•

Technical Standards Part C (Scotland).

The dimensional accuracy of the completed structure should be within the permissible tolerances specified by the manufacturer of elements to be supported by, or accommodated within, the structure.

•

Small Buildings Guide (Scotland).

•

Technical Booklet D (N.Ireland).

•

BS 8103:1.

•

This technical manual.

Where the structural elements of a building are designed by more than one Expert, then one Expert should be nominated to be responsible for certifying the overall stability of the structure. To ensure durability, materials should generally be selected as follows to suit the exposure of a particular location: •

BS 5628 – masonry units and mortar.

•

TRADA Floor Span Tables.

•

BS 8110 – concrete.

•

BS 5268 and BS EN 338 – structural timber.

•

BS 5950 – structural steel.

The findings and recommendations of any site investigation report should be considered when selecting materials for below ground use. 13

Where prefabricated structural components rely on additional site fixed elements or fixings for their own stability, or provide stability to other elements, then a nominated person should be responsible for ensuring that all necessary assembly information is supplied to site and that the completed work complies with the design. Prefabricated structural components should not be altered on site or any major repair carried out without the specific approval of the expert responsible for the design. Prefabricated structural components should be clearly identified by indelible marking. The rigidity of a framed structure should be enough to prevent damage or visual defects occurring to all elements within or supported by the structure. Workmanship on building sites should comply with BS 8000 and Regulation 7 to the Building Regulations.

Inspections

2.0 Introduction International Construction Warranties Limited will carry out targeted inspections on new, converted and refurbished properties. The main purpose of carrying out inspections is to reduce chances of latent defects through a tightly targeted programme of risk management. Each development being assessed on its merits including; the complexity of the site, site environment, method of construction and the experience of the developer / builder. When registering your site with us, you will receive contact details of your allocated International Construction Warranties Limited surveyor or appointed Approved Inspector, with who you can arrange your first site visit. In order for us to gather a full understanding of your development and what you wish to achieve, your appointed surveyor will arrange a pre-planning meeting with your site manager with the purpose of discussing the development as a whole, including programme of works and the method of construction. Following this meeting your appointed surveyor will discuss your risk management programme, targeting site inspections to suit the agreed stages of the development. Our Inspection programme of risk management cannot eliminate all risks but together with the following stage inspection memoirs will endeavour to: •

Reduce any uncertainties.

•

Minimise the risk of defects going undetected.

•

Increase satisfaction of the new building user whether this be residential.

•

Reduce the likelihood of claims e.g. For the Builder/ Developer during the two-year defect liability period and for the End Insurer of the Policy.

The number of inspections carried out on the construction of your development will vary depending on initial and on-going risk management assessments carried out by your appointed surveyor. These occur at four different stages throughout the course of the build in order to identify areas where assistance can be given to reduce the number of latent defects at a particular stage. Not all stages of the build will require inspection from your appointed surveyor as some may be inspected by your local authority building control department.

The programme of risk management Inspections is planned to cover all significant structural and weather penetration elements. At each inspection, your appointed surveyor records all the data gathered and provides a site generated report for each plot where technical advice is given, or a defect is recorded. The following inspection overview will indicate the elements of construction that should be completed and will allow the site manager to check works during the built to completion and provide an indication into the aspects of construction your appointed surveyor will want to inspect. The recorded information is held by International Construction Warranties Limited providing an on-going record of information for each plot. This provides an invaluable source of management data and, as a unique service to our clients; we can offer a regular reporting service. Please note: Works that are not acceptable to International Construction Warranties Limited will require rectification before an Insurance certificate can be produced.

Construction Stage Stage 1 Commencement of site/Site Overview/ Foundations to ground floor Stage 2 Excavations Stage 3 Foundations and Sub-structure Stage 4 Ground floor to upper floors Stage 5 Upper floors to Roof Stage 6 Pre-Plaster / Plasterboard Stage 7 Completion

2.1 Site and Construction Overview Stage (01) Checklist

Item of construction to be quality checked

Builder Check

ICW Inspect

General â&#x20AC;&#x201C; The ICW surveyor will check all details on-site are identical to those quoted and uploaded onto the SmartSurv Inspection Application i.e. Plot numbers, site address, contact details etc.

ICW surveyor to introduce themselves and to take note of Site agents name and contact details.

Check that all proposed plots under the current phase have been registered and that the plot numbers on- site are as those described on the SmartSurv application.

ICW surveyor to explain the on-site paperwork and inspection recording system.

Site wide elements - the ICW surveyor will discuss the type of construction to be adopted together with general observations on the ground conditions, foundation type and site wide elements.

The ICW surveyor will discuss the principles of the development on the following issues: Construction type - traditional or non-traditional or modern methods of construction. Exposure conditions of the site, have they been considered in the design. Are there any rooms to be constructed below ground (habitable or non habitable and if so, are insurance backed guarantees going to be provided). Ground conditions: - type of subsoil - water table level - contaminants, gas etc - shrinkability if clay and trees (present or removed) - foundation design (standard / engineered) - difficult site condition i.e. sloping site - land drainage required Sound insulation: - are RSDâ&#x20AC;&#x2122;s to be used, unique numbers required - pre completion testing is this by UKAS or ANC member - from Approved Doc E pre completion testing required Is this by UKAS or ANC member

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

2.1

Item of construction to be quality checked

Builder Check

ICW Inspect

General â&#x20AC;&#x201C; The ICW surveyor will check all details on-site are identical to those quoted and uploaded onto the Smartsurv inspection application i.e. plot numbers, site address, contact details etc.

Foundations discussed in detail to establish the type and design: - strip - raft - piled - other - existing ground obstructions - sulphates in the ground (cement considerations) Tanking: - are there any walls to be tanked or require tanking - are there any basement areas and what is proposed to prevent water ingress, attention to detailing of junctions - structural design, wall, floor construction - ventilation, fire resistance and means of escape in case of fire services passing through and land drainage around perimeter - is an Insurance backed Guarantee to be provided Drainage: - mains drainage, foul and surface water - MH size and location, gradients and protection - non-mains drainage - septic tank / treatment plant / cesspool - size and location - vehicular access required - outfalls and porosity tests - soakaways - size, location and ground conditions (porosity tests) - land drainage Ground floor type: - ground bearing - beam and block or similar type - cast insitu concrete - timber

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

2.1

Item of construction to be quality checked

Builder Check

ICW Inspect

External wall type: - masonry cavity / solid - timber frame - steel frame - concrete frame / panel â&#x20AC;˘ other External wall insulation: - full fill - partial fill - clear - other Movement joints: - location - type/design - Restraint

Internal walls: - partition walls - type, loadbearing / non loadbearing - foundations - party walls - masonry - solid - cavity - dry lined or dense plaster - timber framed - metal framed

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

2.1

Item of construction to be quality checked

Builder Check

ICW Inspect

Upper floors: - floor type - timber, concrete, other - spans - fire resistance - insulation Party floor: - floor type - timber, concrete - sound performance - density or isolation

Roof - pitched, flat, mansard, other: - timber, steel, other - trusses or cut - fixing details Roof covering: - slates, tiles, thatch, high performance felts, lead, other - fixing specification - nailing / clipping, manufacturers details Roof penetrations: - chimneys - stability and trays / flashings - parapets / copings - stability and trays / flashings - vents -flashings - roof lights - consider design, trimming and weathering

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

2.2 Excavations Stage (02) Checklist

Item of construction to be quality checked

Builder Check

ICW Inspect

General â&#x20AC;&#x201C; items checked during this inspection will cover the quality of build and structural stability / future weather integrity of the structure from foundation to ground floor level.

Ground Conditions - type of subsoil - water table level - contaminants, gas etc - shrinkability if clay and trees (present or removed) - foundation design (standard / engineered) - difficult site condition i.e. sloping site - land drainage required

Foundations in place and constructed to comply with the Building Regulations and/or the relevant British Standards, checks made: - strip - raft - piled - other - existing ground obstructions - sulphates in the ground (cement considerations)

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

2.3 Foundation to Ground Floor Stage (03) Checklist

Item of construction to be quality checked

Builder Check

ICW Inspect

Load bearing walls from foundation to dpc: - bricks and blocks below dpc - selection of bricks - resistance to ingress of moisture Basements: - ensure that all tanking is correctly installed and linked to the dpc and dpm above of the above ground structure

Floors - all floor substructures in place and constructed to comply with the Building Regulations and or the relevant British Standards, checks made for: - timber - size, centres, spans and grading of joists - fixings and bearings - multiple and trimming members - adequate ventilation - restraint straps and noggins - concrete - size and bearing of units - damaged units and no cavity obstructions - trimming of openings - adequate support to internal partitions - service entries filled - all dpcs linked to suitable dpmâ&#x20AC;&#x2122;s

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

2.3

Item of construction to be quality checked

Builder Check

ICW Inspect

Walls - all walls to be plumb and structurally stable, checks made for: Masonry: - dpcs lapped and bedded on a smooth joint - dpcs in place around all openings - wall ties correctly specified and placed - joints filled and consistent in width and height - cavities free of debris - insulation correctly located, secured and clean - lintel bearings and beam supports correct Timber / steel frame system: - sole plate preparation and fixing adequate - plumb - correct specification used in make up - cavity barriers correctly located - damage, notching and drilling of members - wall ties and lintels suitable for purpose - breather membrane intact Internal walls: - built off adequate support - masonry joints filled - bonding adequate Lintels and bearings

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

2.4 Ground Floor to Upper Floor Stage (04) Check List

Item of construction to be quality checked

Builder Check

ICW Inspect

General - items checked during this inspection will cover the quality of build and structural stability / future weather integrity of the structure from dpc to upper floor level.

Walls - all walls to be plumb and structurally stable, checks made for: Masonry: - restraint straps and noggins in place - dpcs suitably lapped and bedded on a smooth joint - dpcs in place to all openings - insulation correctly situated, secured and clean - wall ties correctly specified and placed - joints filled and consistent in width and height - lintel bearings correct and beam supports checked - cavities free of debris Timber / steel frame system: - sole plate preparation and fixing adequate - plumb - correct specification used in make up - cavity barriers correctly located - damage, notching and drilling of members - wall ties and lintels suitable for purpose - breather membrane intact

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

2.4

Item of construction to be quality checked

Builder Check

ICW Inspect

General - always refer to the â&#x20AC;&#x2DC;Superstructure to Upper Floors (02) check listâ&#x20AC;&#x2122; in addition to this list. Items checked during this inspection will cover the quality of build and structural stability / future weather tightness of the structure from upper floor level to, but excluding, roof construction.

Floors - all floor substructures in place and constructed to comply with the Building Regulations and or the relevant British Standards, checks made for: Timber: - size, centres, spans and grading of joists - damaged units - fixings and bearings - multiple and trimming members - restraint straps and noggins Concrete: - size and bearing of units - no cavity obstructions - trimming of openings Party floors: - joints filled - correct density - floating layer - junctions detailed Adequate support to internal partitions Service entries filled

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

2.4

Item of construction to be quality checked

Builder Check

ICW Inspect

General - always refer to the â&#x20AC;&#x2DC;Superstructure to Upper floors (02) check listâ&#x20AC;&#x2122; in addition to this list. Items checked during this inspection will cover the quality of build and structural stability / future weather tightness of the structure from upper floor level to, but excluding, roof construction.

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

2.4

Item of construction to be quality checked

Builder Check

ICW Inspect

Party walls: - density / isolation adequate and maintained - joints filled - junctions detailed - party wall sock to external cavity - no mix and match of materials - penetrations - wall ties to correct specification Chimneys and parapets - ensure that: - all cavity trays and flashings are correctly situated (two number proprietary lead trays dressed up around flue) - check liners correctly placed and joints sealed - the chimney is correctly sized for stability and located the correct height above pitch line - the masonry and the flaunching is correctly pointed - copings correctly restrained / securely fixed - cavity trays (stepped) correctly located and lapped into soakers and flashings - mortar mix is suitable

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

2.5 Upper Floors to Roof Structure Stage (05) Check List

Item of construction to be quality checked

Builder Check

ICW Inspect

General - always refer to the â&#x20AC;&#x2DC;Upper floors to Pre-Plaster including Roof Structure (03) check listâ&#x20AC;&#x2122; in addition to this list. Items checked during this inspection will cover the quality of build and structural stability / future weather tightness of the structure up to pre-plaster and including, roof construction. The structure may not yet be fully weather tight.

Floors - all floors (including party floors) in place and constructed to comply with the Building Regulations and or the relevant British Standard Walls - all walls to be plumb and structurally stable, cavities free of debris Roofs - all roofs to be constructed and structurally stable, checks made for: - centres and sizes of joist, binders, purlins, struts and or trusses - fixings of timbers / members - trimming to openings - proximity of timbers to chimneys/ flues - damage and or notching / drilling - restraint straps and noggins in place - bracing - size, location and fixing - valley, hip and dormer roof details - penetrations and weathering - party and gable wall cut to profile - external wall insulation in place to prevent cold bridging and cavity closed at eaves level - ensure that the batten sizes, spacing and fixings are compatible with the covering and each other - cavity barriers provided where appropriate Chimneys and parapets - ensure that: - all cavity trays and flashings are correctly situated - the chimney is correctly sized for stability and located the correct height above pitch line - the masonry and the flaunching are correctly pointed

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

2.6 Pre-Plaster / Plasterboard Stage (06) Check List

Item of construction to be quality checked prior to covering with plasterboard etc.

Builder Check

ICW Inspect

General - all structural items should be in place and completed, namely floors, walls, roof structure, staircases etc. In addition all services, â&#x20AC;&#x2DC;first fixâ&#x20AC;&#x2122;, should be undertaken or almost complete.

Floors - all floors in place and constructed to comply with the Building Regulations and or the relevant European Standards, checks made for: - holes within floors - fire stopping - notching / drilling of joists - damaged floor units - fixing of boards / floating floors preparation - vapour barriers - party floors - joints filled - correct density - floating layer - junctions detailed - adequate support to internal partitions - plasterboard / plain edge board supports - correct centres and sizes of joists Walls - all walls to be plumb and structurally stable, checks made for: - dpcs in place at all openings and linked to dpm at floor - restraint straps and noggins in place - chasing to walls for sockets and fittings - party walls - joints filled - junctions detailed - no mix and match of materials - bearings to joist, lintels and beams

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

2.6

Item of construction to be quality checked prior to covering with plasterboard etc.

Builder Check

ICW Inspect

Roofs (internally) - all roofs to be weather-tight and structurally stable, checks made for: - centres and sizes of joist, binders, purlins, struts and or trusses - fixings of timbers / members - trimming to openings - proximity of timbers to chimneys/ flues - damage and or notching / drilling - restraint straps and noggins in place - bracing - size, location and fixing - valley, hip and dormer roof details - penetrations and weathering - party and gable wall cut to profile and fire stopped (where applicable) - flue and vent connections - felt condition and laps - insulation (if fitted at time) - continuity with external wall insulation - cross ventilation / warm roof detail

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

2.6

Item of construction to be quality checked

Builder Check

ICW Inspect

Services - generally all services and service paths should be fitted in accordance with the appropriate British Standard and/or governing bodies guidance.

Electrical - ensure that all works have been installed in accordance with the IEE Regulations. Checks made for: - location of cable runs within floor and wall constructions - vertical and horizontal from sockets / switches - need for earthed protection - socket and switch heights Gas / solid fuel - ensure that all works have been installed by a Corgi registered fitter. Checks made for: - location and protection - serviceability / access - ventilation Plumbing - ensure all pipes are correctly clipped / fixed and protected.Check made for: - location and sizing of pipes - protection passing through walls / floors - damage - backfalls - connections

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

2.6

Item of construction to be quality checked

Builder Check

ICW Inspect

Services - generally all services and service paths should be fitted in accordance with the appropriate British Standard and/or governing bodies guidance.

Miscellaneous: - staircases - ensure that the staircase has a minimum suitable width, the correct headroom, pitch, riser and going, together with a correctly located and fixed handrail and balustrading - first fix carpentry in place, plumb and square - fireplaces, hearths and chimneys properly constructed - windows - frames appropriately fixed and glazing installed correctly Conservatories Ensure that they are constructed to the same standard as the remainder of the home and form a weather tight and stable addition to the house. In addition, ensure that cavity trays are installed as per any other abutment. Integral garage Ensure that it is finished internally to a reasonable, basic level of decoration appropriate for its intended use. It is weathertight (not necessarily watertight, 100mm brick wall) and where abutting the house incorporates a suitable cavity tray and flashing. Ensure firestopping is complete. Basements Ensure that all tanking is correctly installed and linked into the cavity tray, dpc and dpm of the above ground structure.

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

2.6

Item of construction to be quality checked

Builder Check

ICW Inspect

Structure - ensure that brickwork / rendering and roof covering is of a consistent nature in quality of finish and workmanship. All window and door frames must be reasonably sealed where abutting the external envelope to prevent weather penetration.

External walls: Rendering: - should be durable to resist the weather and impact - should not bridge the dpc Masonry: - should be matched in colour and texture providing reasonable aesthetics - joints should be filled / pointed and consistent - mortar should be durable and consistent in colouring - corbelling and or plinths should not be excessive, thus enabling water to collect General: - movement joints should be suitably located and filled - weepholes should be evident at all locations of cavity projections and at dpc level within timber frame construction â&#x20AC;&#x201C; ensure that surfaces are reasonably plumb and level - lead flashings should be correctly located and fixed - dpc should not be bridged and located a min. 150mm above finished external ground level Level thresholds Should be suitably constructed to prevent damp ingress and allow adequate entry to the dwelling via a wheelchair

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

2.6

Item of construction to be quality checked

Builder Check

ICW Inspect

Windows and doors: - ensure that all windows and doors are - suitably decorated to a reasonable visual standard and to provide weather protection to the home - designed in such a way to shed water from the external envelope - provided with a suitable deterrent against a forced entry - ensure that brickwork and stone cills and heads shed water and are not damaged / cracked Roofs (externally): - ensure that the batten sizes, spacing and fixings are compatible with the covering and each other - all finishes (tiles, slates, lead or felt) should be free from damage, laid to falls where appropriate and finished to a basic visual standard - all coverings should be nailed, fixed, clipped to the correct specification in accordance with the relevant British/European Standards or the manufacturersâ&#x20AC;&#x2122; details - coverings and gauge are suitable for pitch - all flashings and trays are correctly specified and positioned Chimneys and parapets - ensure that: - all cavity trays and flashings are correctly situated - the chimney is correctly sized for stability and located the correct height above pitch line - the cowling is correctly fitted (where applicable) - the masonry and the flaunching is correctly pointed

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

2.7 Completion Stage (07) Checklist

Item of construction to be quality checked

Builder Check

ICW Inspect

Roof space - the roof space should be accessible, with all insulation in place and, where fitted (in a cold roof) the loft hatch must be insulated and secured with a catch. Access must be provided to and around the water storage tanks within the loft space.

Roof void, ensure that: - all flues terminate at the outside air via a proprietary terminal outlet - all tanks and pipes are adequately supported and insulated - all SVP and ventilation outlets are discharged adequately - restraint straps are correctly positioned and supported / blocked - bracing (where applicable) to the structure is adequately sized, fixed and positioned - insulation is adequate and correctly positioned (continuous) - all ducting in loft is adequately insulated - underfelt is continuous and not damaged - ‘warm roof’ - the roof void is completely sealed - ‘cold roof’ - adequate cross ventilation is maintained and unobstructed - check size, centres and damage to structural members forming the roof structure Miscellaneous Provide evidence of warranty backed insurance guarantees where applicable. The whole house should be clean, free from builders materials /rubble and be complete prior to handover / conveyance: Staircases Ensure that the staircase has a minimum suitable width, the correct headroom, pitch, riser and going, together with a correctly located and fixed handrail and balustrading Flooring All flooring to be laid reasonably level and smooth to accept the intended finish. All boarding to be fixed securely to avoid squeaking, with floating floors to be adequately supported at door openings

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

2.7

Item of construction to be quality checked

Builder Check

ICW Inspect

Conservatories Ensure that they were constructed to the same standard as the remainder of the home and form a weathertight and stable addition to the house. Integral garage Ensure that it is finished internally to a reasonable basic level of decoration, appropriate for its intended use. It is weathertight (not necessarily watertight, 100mm brick wall) and where abutting the house incorporates, a suitable cavity tray and flashing. Ensure firestopping is complete. Sound insulation - are RSD’s compliance certificates available - pre completion testing reports available from a UKAS or ANC member The following guarantees should be provided ‘where applicable’: - basement tanking, materials and workmanship insurance-backed 10-year warranty - timber treatment, materials and workmanship insurance-backed 10-year warranty - chemical injection damp-proofing, materials and workmanship insurance-backed 10-year warranty - remedial wall tie replacement, materials and workmanship insurance- backed 10-year warranty

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

2.7

Item of construction to be quality checked

Builder Check

ICW Inspect

Ground works and drainage - generally all external decorations should be complete, boundary walls built, drainage connected and tested, paths and drives complete / serviceable and the plot free from any builderâ&#x20AC;&#x2122;s debris.

Drainage All foul and surface water drainage should be connected, tested and fully operational. Where non-mains drainage is incorporated, it should be sited so as to allow suitable maintenance and emptying (as should filling any form of storage tank, i.e. oil). Ensure land drainage is present where necessary, i.e. water logging likely within 4m of the dwelling. Display robust notice plates indicating maintenance and operating requirements for non-mains drainage and oil fuel storage systems. Boundary, retaining or garden walls To be complete and structurally stable. Paths, drives and patios To be laid to reasonable, self-draining falls and suitable to take their intended loading, i.e. the weight of a tanker if storage or septic tanks are located too far from the highway. No path, patio or drive should be within 150mm of the dpc to the external wall of the house or garage. Level thresholds Should be suitably constructed to prevent damp ingress and allow adequate entry to the dwelling via a wheelchair. Planting Ensure that any planting scheme introduced has been designed to suit the foundations already constructed. Superstructure Ensure that all finishes are to a reasonable basic visual standard, the brickwork / rendering and roof covering is of a consistent nature in quality of finish and workmanship. All windows and door frames must be reasonably sealed where abutting the external envelope to prevent weather penetration. All rainwater goods must be in place and connected to the drainage system and all timber products are suitably treated / decorated to give a reasonable finish and protection against the elements.

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

2.7

Item of construction to be quality checked

Builder Check

ICW Inspect

External Walls: Rendering: - should be durable and decorated to resist the weather and impact - should not bridge the dpc Masonry: - should be matched in colour and texture providing reasonable aesthetics - joints should be filled / pointed and consistent - mortar should be durable and consistent in colouring - corbelling and / or plinths should not be excessive, thus enabling water to collect General: - movement joints should be suitably located and filled - weepholes should be evident at all locations of cavity projections and at dpc level within timber frame construction - ensure that surfaces are reasonably plumb and level - lead flashings should be correctly located and fixed - dpc should not be bridged and located a min. 150mm above finished external ground level

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

2.7

Item of construction to be quality checked

Builder Check

ICW Inspect

Superstructure - ensure that all finishes are to a reasonable basic visual standard, the brickwork / rendering and roof covering is of a consistent nature in quality of finish and workmanship. All window and door frames must be reasonably sealed where abutting the external envelope to prevent weather penetration. All rainwater goods must be in place and connected to the drainage system and all timber products are suitably treated / decorated to give a reasonable finish and protection against the elements.

Windows and Doors: Ensure that all windows and doors are: -

suitably decorated to a reasonable visual standard and to provide weather protection to the home designed in such a way to shed water from the external envelope provided with a suitable deterrent against a forced entry ensure that brickwork and stone cills and heads shed water and are not damaged / cracked

Roofs: - all finishes (tiles, slates, lead or felt) should be free from damage, laid to falls, where appropriate, and finished to a basic visual standard - all rainwater goods should be in place laid to appropriate falls and connected to the drainage system - all fascias and soffits should be decorated to a basic visual finish and to protect them from the elements Chimneys and parapets - ensure that: - all cavity trays and flashings are correctly situated - the chimney is correctly sized for stability and located the correct height above pitch line - the cowling is correctly fitted (where applicable) - the masonry and the flaunching is correctly pointed

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

Site Investigation

3.0 Site Investigation Planning Permission

Walk over survey

There may be specific planning conditions attached to the planning permission relevant to site investigation and contaminants. As a minimum requirement the developer should provide a report of the desk study and site reconnaissance or other times known as the walk-over. This will, in some cases, be enough to develop a conceptual model of the source of contamination and pathways by which it might reach vulnerable receptors.

It is the responsibility of the developer to complete the site walk over survey prior to any construction activity taking place. Guidance regarding the process of the walk over study can be found in BS 5930: 2015 Code of Practice for ground investigations.

Site Investigation All site investigations to be carried out in compliance of BS 5930: 2015 Code of practice for ground investigations.

Desk Study Prior to any work commencing on-site a detailed desk top study should be carried out in accordance with BS 5930: 2015 Code of Practice for ground investigations. Section 2 of the British Standard identifies key specifics associated with the site, these are as follows: Site Details: The location, to include address and grid reference, the site boundaries and ownership of the land, the current use of the land and its topographical status as well as the location of site services such as gas, water, electric, foul and surface water. Consideration must also be given to the sites environmental and protected status.

As a minimum the walk over survey should identify: •

Topography

•

Water Courses

•

Contamination

•

Site Constraints

•

Vegetation and location of trees

•

Existing buildings

•

Services

•

Wildlife and Ecology

Once completed the information from the desk top study and walk over survey should be completed in a report format to ascertain whether a further detailed examination is required.

Site History: Photographic evidence, such as aerial and satellite imagery, the location of surrounding watercourses and potential flooding, site data such as the environment agency flooding map should be used. Any changes in topography or evidence of unstable ground, mine workings, tunnels, pipework’s and cable locations. Areas of specific scientific interest, historical significance and archaeological importance.

3.0

Site Geology Information regarding the site geology can be found from a variety of sources and basic guidance can be seen in table 1.

Investigation Type

Examples of Information

Geology

Site topography Topographical maps Geological maps Geological publications Regional guides Soil survey maps and records Previous planning application

Site Topography

Topographical maps Ordnance survey data Site photography Ariel Photography Previous planning applications

Groundwater Conditions

Environment agency flood maps Previous planning applications Previous ground investigation reports

Existing Services

Statutory undertakersâ&#x20AC;&#x2122; maps Visual identification

Previous Land Use

Topographical maps Geological maps Aerial photography Archaeological records Mining records Previous planning applications Site knowledge

Table 1 Guidance

3.0

Detailed Site Investigation

Site Management Requirements

In the event a detailed investigation is required the developer should follow the guidance provided in this section.

Once the necessary site investigations have been completed, (If required) there should be a full proposal submitted for all the works that will include as a minimum:

Geotechnical Investigation

Risk assessments To review design measures and remedial treatments in order to ensure the ground is fully remediated prior to the commencement of work.

Examples would be: trial pits and trenches, hand auguring, power driven auger boreholes, dynamic sampling using window or windowless sampling tubes, cable percussion boreholes and cone penetration. It is recommended that a suitable grid system is utilized to ensure the whole of the site has adequate investigation techniques applied.

Contamination Investigation Should contaminants be identified through the geotechnical investigation, then a detailed site investigation will be required, following guidance in BS 10175:2011 Investigation of potentially contaminated sites - Code of practice (+A1:2013)

Laboratory Testing Guidance on laboratory testing can be found in BS 10175:2011 Investigation of potentially contaminated sites - Code of practice (+A1:2013) and should always be followed in the event of site contamination being identified on site.

Design Proposals To monitor the works during construction, and to apply appropriate ground improvement or remediation when required. Remediation To ensure that all method statements for the proposed remediation works is available, monitored and where necessary amended to consider on-going problems, this should include that all records are kept. Site Reports Photographic evidence, site notes, site survey information, remedial works reports, soil removal and imports, post remediation sampling, waste transfer notes and validation reports.

Guidance can also be sought in BS 5930: 2015 Code of practice for ground investigation

3.0

Please see Figure 1.0 for basic guidance.

Have contaminants been identified on the site?

Assessment based on the desk top-study and walk over survey

Have any hazards been identified on the site?

YES

Carry out a more detailed site investigation

Ok to commence work with monitoring on site

YES

Carry out a more detailed site investigation

Provide reports identifying contamination/ hazards on site

Provide reports identifying remedial action to be taken

Complete remediations as identified 41

Provide copies of all reports confirming all remedial works have been completed and tested

Foundations

4.0 Foundations Statutory Requirements

Materials

Roles and Responsibilities

All materials used shall:

When considering foundation type and depth this should be linked directly to the site investigation report. It is the responsibility of the developer to ensure the correct foundation is provided and inspected by the Building Control body prior to any concrete being poured.

- Be adequately protected and stored in a correct manner. - Comply with relevant British Standards or equivalent European Technical Specification with the certification available for inspection by ICW. - Be installed as per Manufacturers details. - Have a life span of 60 years when used as part of the structure. However, it is accepted that materials that are not an integral part of the structure may require maintenance and or replacement within this period.

Building Regulation Requirements The requirements of Approved Document A, section 2E, of the Building Regulations 2013 should be followed, and all relevant approvals sought from the Building Control Body. Where calculations are required to support the proposed design, these should be produced by a suitably competent and qualified person and made available for the approval of ICW. Foundations shall be designed to ensure that the building is appropriately supported at all times without excessive settlement and any strip foundation exceeding 2.5m will require structural engineerâ&#x20AC;&#x2122;s calculations and design.

Design Where a specialist design is requested or required, they shall: - Be designed by a suitably qualified person. - Be supplied with clear precise instructions. - Be supported with structural calculation when outside the guidance of the Approved Documents. - Be available for inspection by ICW .

Workmanship During the construction phase: -

All workmanship must be completed in a competent workmanship like manner. Protected against unnecessary damage. Design and Installation specifications are followed. Products and materials are inspected for suitability for their purpose.

4.1 Strip and Trench Fill Foundation Foundation Types â&#x20AC;&#x201C; Plain Concrete Strip Foundation

Trench Fill Foundation

Should generally be a minimum of 600mm in width, depending on the overall wall thickness, the design should take in to account the ground conditions and be in accordance with the table 1. The foundation concrete should have a minimum thickness equal to the projection or 150mm (whichever is greater).

Should generally be a minimum of 450mm in width, depending on the overall wall thickness, the design should take in to account the ground conditions and be in accordance with the table 1.

The foundation concrete should have a minimum thickness of 500mm.

4.2 Minimum Depth of Strip Foundations Ground conditions must always be established as part of the initial site investigation, and guidance found in the requirements of Approved Document A of the Building Regulations 2013 page 5, should be followed, and relevant approvals sought. Where ground conditions are susceptible to frost action, the foundation should have a minimum depth of 0.45m to the underside, this depth however will be subject to change in relation to loading and weather conditions at the time of excavation. In shrinkable soils, which are subject to volume change, the Modified plasticity index must be considered when determining the minimum depth as follows:

Modified Plasticity Index

Volume Change Potential

Minimum Depth (mm)

<10

Low

750

20-40

Medium

900

40-60

High

1000

>60

Very High

Refer to specialist advice

4.3 Concrete Mix General purpose concrete mixes should be suitable for the end use and be specified in accordance with BS 8500-1 and BS 8500-2.

Location for Use

Site Mixed

Ready Mix

Consistency

Strip Foundation

GEN1

ST2

Trench Fill Foundations

GEN1

ST2

Mass Concrete Foundations (others)

GEN1

ST2

Cavity Wall Fill

GEN1

ST2

4.3

Total load of load-bearing walling not more than Type of Ground (including engineered fill)

Condition of Ground

Field Text Applicable

Minimum width of strip foundation (mm)

Rock

Not inferior to sandstone, limestone or firm chalk

Requires at least a pneumatic or other mechanically operated pick for excavation.

Equal to the width of the wall plus 50mm each side.

Gravel Sand

Medium dense

Requires pick for excavation. Wooden peg 50mm square in cross-section is hard to drive beyond 150mm.

250

300

400

500

600

650

Clay/Sandy Clay

Stiff

Can be indented slightly by thumb.

250

300

400

500

600

650

Clay/Sandy Clay

Firm

Thumb make impression easily.

300

350

450

600

750

850

Sand/Silty Sand/Clayey Sand

Loose

Can be excavated with a space. Wooden peg 50mm square in cross-section can be easily driven.

400

600 Does not fall within the provisions of this guidance where the total load exceeds 30kN/linear m.

Silt/Clay/Sand Clay/Clay or Slit

Soft

Finger can be pushed in up to 10mm.

450

Silt/Clay/Sand Clay/Clay or Silt

Very soft

Finger can be easily pushed in up to 25mm.

Refer to specialist advice.

650

4.4 Stepped Foundations Foundations stepped on elevation should overlap by twice the height of the step, by the thickness of the foundation, or 300mm, whichever is the greater (see Fig. opposite). Trench fill foundations should have an overlap of twice the height of the step or 1.0m, whichever is the greater. Steps in foundations should not be of greater height than the thickness of the foundation. Refer to Section 2E2 of Approved Document A of the latest Building Regulations.

4.5 Engineered Foundations All engineered foundations such as piled and raft foundations should be designed by a suitably qualified structural engineer, the details, drawings, technical guidance, ground conditions and calculations should be made available for inspection.

4.6 Engineered Fill Any engineered fill material used for foundations should be carefully selected and have the appropriate documentation to be classed as an engineered fill.

â&#x20AC;˘

Sound fill with correct material and capable of compaction, provided with starter, and should be compacted no greater than 5 times its nominal value.

In designing and specifying a fill which is to form a foundation, the following technical requirements should be established: â&#x20AC;˘

The excavation must be well constructed, free from contaminants, areas of poor strata removed and well drained.

4.7 Piled Foundation Where the bearing capacity of the soil is poor or imposed loads are very heavy, pile foundations are required. There are two main types of pile; end bearing piles, where the pile acts as a column carrying the load down to the bearing strata, and friction piles, where the load is gradually transferred along the length of the pile. There are two basic construction methods; bored piles, in which the concrete is cast in place, and precast concrete piles that are driven into the ground. With cast in place piles, the hole is bored into the ground, a reinforcement cage installed, and the hole gradually filled with concrete. Precast concrete piles may be square, octagonal or other shape in cross section. They may be cast to the full length required or units may be joined to form longer lengths. Precast piles need heavier reinforcement than cast in place piles as it is required to carry the stresses due to transportation and installation as well as the final loads from the structure. Alternatively, they may be pre-stressed. Depending on the nature of the ground, the piles may be supplied with a cast iron or steel shoe to aid driving. As a combination of the two methods of construction, precast concrete shells may be driven into the groundand the interior filled with concrete.

4.8 Raft Foundation A raft foundation consists of a raft of reinforced concrete under the whole of a building. This type of foundation is described as a raft in the sense that the concrete raft is cast on the surface of the ground which supports it, the foundation is not fixed by foundations carried down into the subsoil. Raft foundations may be used for buildings on compressible ground such as very soft clay, alluvial deposits and compressible fill material where strip, pad or pile foundations would not provide a stable foundation without excessive excavation. The reinforced concrete raft is designed to transmit the whole load of the building from the raft to the ground where the small spread loads will cause little if any appreciable settlement. When the option of a raft foundation has been chosen this must be designed by a suitably qualified engineer and the design must be available for inspection. Reinforcement must be installed and supported as per the design.

Volume Change Potential Low

Medium

High

Void dimension against side of foundation and ground beam

0mm

25mm

35mm

Void dimension under ground beams and suspended in-situ concrete ground floor

50mm

100mm

150mm

200mm

250mm

300mm

Void dimension under suspended precast concrete and timber floors

4.9 Foundations and Trees If trees are within the area if influence of the proposed foundations, appropriate measures must be taken to counter the potential effect of changes in ground conditions in shrinkable clay soils. This is relevant to any tree regardless of size and maturity. Foundations affected by trees with a depth of more than 1.5m should be provided with protection from heave in the form of a compressible material, which should be installed to the inside surface of the foundation. The compressible material should be placed 500mm above the bottom of the foundation. It is recommended that manufacturers installation guide is utilised.

Distance to Tree (m) Water Demand

Tree/height (m)

Hawthorn (10m)

Weeping Willow (16)m High water demand Broad-Leaf English oak (20m)

English Elm (24m)

Soil Volume Change 2

High

2.5

1.5

Medium

2.5

1.35

0.9

Low

2.25

1.8

1.1

0.75

High

2.25

1.65

Medium

2.5

1.95

1.45

0.9

Low

2.35

2.1

1.65

1.2

0.75

High

2,5

1.5

Medium

2.2

1.75

1.35

0.9

Low

2.4

2.25

1.8

1.45

1.1

0.75

High

2.25

1.85

1.45

Medium

2.3

1.95

1.6

1.25

0.9

Low

2.4

2.25

1.95

1.65

1.35

1.05

0.75

4.9

Distance to Tree (m) Water Demand

High water demand Coniferous

Tree/height (m)

Leyland Cypress (20m)

Soil Volume Change 2

High

2.5

1.5

Medium

2.15

1.25

0.9

Low

2.25

1.8

1.05

0.75

High

2.1

1.65

Medium

1.8

1.4

0.9

Low

1.45

1.15

0.75

High

2.2

1.9

1.4

Medium

1.85

1.6

1.2

0.9

Low

1.5

1.3

0.75

High

2.25

2.05

1.65

1.25

Medium

1.9

1.7

1.4

0.9

Low

1.5

1.3

0.75

High

1.4

1.25

Medium

1.7

1.25

0.9

Low

1.4

0.75

High

1.5

Medium

1.3

0.9

Low

1.05

0.75

High

1.6

1.25

Medium

1.35

1.1

0.9

1.1

0.9

0.75

Apple/Plum/Pear (10m)

Moderate water demand Broad-Leaf

Alder/maple/Walnut (18m)

Beech/Horse Chestnut/ Sycamore (20-24m)

Moderate water demand Coniferous

Pine/Larch/Spruce (18-24m)

Fig/Hazel/Elder (8-10m) Low water demand Broad-Leaf Holly/Laburnum/Birch (12-14m)

Low

4.10 Construction Principles Strip/Trench Fill Foundation

Piled Foundation

•

Setting out is true and accurate to the design.

•

Pile log is onsite and ready for inspection.

•

Excavations have been formed neatly with well-trimmed sides and bottom.

•

All piles are in the correct locations.

•

Minimum depths have been calculated and achieved.

•

Alignment and spacing is accurate.

•

Minimum widths have been calculated and achieved.

•

No visible damage to piles.

•

Steps have been formed correctly.

•

Soft spots have been removed or designed out.

•

Where reinforcement is required it is installed as per the design.

•

Excavations are clean with no loose debris or water present.

•

Heave protection installed as per design (if required) Pilled foundation .

•

Pile log is onsite and ready for inspection.

•

All piles are in the correct locations.

•

Alignment and spacing is accurate.

•

No visible damage to piles.

Raft Foundation •

Setting out is true and accurate to the design.

•

Excavations have been correctly formed.

•

Correct diameter reinforcement has been used.

•

Reinforcement is correctly installed with spacers.

•

Laps to reinforcement have been ties as per the design.

•

Excavations are clean with no loose debris or water present.

Sub-Structure

5.0 Sub-Structure Statutory Requirements

Materials

Roles and Responsibilities

All materials used shall:

When considering the substructure, the design should be linked directly to the site investigation report. It is the responsibility of the developer to ensure the correct substructure is provided and inspected.

•

Be adequately protected and stored in a correct manner.

•

Comply with relevant British Standards or equivalent European Technical Specification with the certification available for inspection by ICW.

•

Be installed as per Manufacturers details.

•

Have a life span of 60 years when used as part of the structure. However it is accepted that materials that are not an integral part of the structure may require maintenance and or replacement within this period.

Building Regulation Requirements The requirements of the Approved Documents of the Building Regulations 2013 should be followed, at all times and all of the relevant approvals sought from the Building Control Body. If any calculations are required to support the proposed design, then these should be provided by a suitably competent and qualified person. The calculations will need to be designed so as they safely distribute loads and forces to the foundations.

Design Where a specialist design is requested or required, they shall: •

Be designed by a suitably qualified person.

Workmanship

•

Be supplied with clear precise instructions.

During the construction phase:

•

Be supported with structural calculation when outside the guidance of the Approved Documents.

•

Be available for inspection by ICW.

•

All workmanship must be completed in a competent workmanship like manner.

•

Protected against unnecessary damage.

•

Design and Installation specifications are followed.

•

Products and materials are inspected for suitability for their purpose.

5.1 Walls below DPC Bricks and Blocks Sulphate Attack In saturated brick work soluble salts from certain types of bricks may cause a chemical reaction with a constituent of the Portland cement in the mortar. The surface of the mortar joint will crack, and the inside will crumble and expand, disrupting the brickwork. It is acceptable to use bricks and blocks below DPC where there is no soil borne sulphates present. If sulphates are present then the suitability of the materials should be checked with the supplier/manufacturer.

5.2 Damp Proof Course DPM’s should be designed to meet the requirements of BS EN 13707 or CE Mark to EN 13967 and be a flexible material laid on mortar and lapped at corners and junctions a minimum of 100mm. DPC’s should link to damp proof membranes. Installed DPC’S should be: •

150mm above finished ground level.

•

Link with the DPM.

•

The correct width.

•

Fully bedded.

•

Lapped by 100mm.

When installing a continuous tray, the tray should be: •

150mm above finished ground level.

•

Have an upstand of 150mm.

•

Have a slight projection.

•

Fully bedded.

•

Lapped by 100mm.

•

Link with the DPM.

•

Have weep holes placed at 900mm centres.

Acceptable materials for use as DPCs Bitumen Based Material

BS 6398

Polythene

BS 6515 (min thickness 0.5mm)

Propriety Materials

With manufacturer’s details

5.3 Service Penetrations Any penetrations through the substructure should have been designed and details should be available for inspection, all services should be sleeved where they pass through the structure for future access and maintenance can be carried out. Where drains penetrate the structure there are several recognised methods acceptable.

5.4 Pipes Bedded into Walls Flexible joints are to be installed as per the diagram and set no more than the maximum dimensions given, it is accepted that the second flexible joint may be an inspection chamber.

5.5 Pipes Lintelled Through Walls Sleeve should have a 100mm larger diameter to allow for a clear 50mm movement gap, the ends of the sleeves should be masked on both sides to prevent rodent entry.

5.6 Waterproofing Design When considering the waterproof design the guidance given with in BS 8102 should be followed, Designers should have a suitable qualiﬁcation such as the Certified Surveyor in Structural Waterprooﬁng or similar which should be agreed with ICW prior to commencement of works. The designer must also hold sufficient professional indemnity insurance for the project.

The waterprooﬁng design will consider the appropriate risk assuming the maximum height of water is constant throughout the building’s life. The designer should be contracted in early stages of the build design as the waterproof design may have a direct impact on the structural design of the project.

Waterproofing Grades Grade

General Use

Description

Retaining walls where used to form light wells

Some seepage and damp are accepted

Non habitable areas, storage, plant rooms where the internal finishes are not readily affected by damp

No water penetration although damp patches are acceptable

Habitable Rooms

No water penetration and a dry atmosphere maintained by ventilation

5.7 Types of Waterproofing Common types of waterproofing systems used in structures are defined as Type A, Type B and Type C.

Type A Waterproofing systems are commonly multi coat renders, cement-based coatings, bituminous paints or epoxy coatings. This form of waterproofing provides an unbroken barrier to water. These systems are applied to clean walls and floors and are usually protected and held in place by floor screeds and renders.

Type B Structurally integral protection meaning where the structure itself is constructed as an integral water-resistant shell. Invariably built of reinforced concrete, the basement structure must be designed within certain strict parameters to ensure it is water resistant.

Type C Waterproofing usually utilise pre-formed high-density drainage membranes, channels and sumps. These are designed to direct any water entering the structure back out in a controlled and managed manner. Cavity drain membranes are installed in the walls and floors, these direct waters into drainage channels. The channels then allow water to be directed to sumps or drains so that it can be removed safely from the building.

Drainage

6.0 Drainage Statutory Requirements

Materials

Roles and Responsibilities

All materials used shall:

When considering drainage, the design should be linked directly to the site investigation report. It is the responsibility of the developer to ensure the correct drainage is provided and inspected prior to covering over.

•

Be adequately protected and stored in a correct manner.

•

Comply with relevant British Standards or equivalent European Technical Specification with the certification available for inspection by ICW.

•

Be installed as per manufacturers details.

•

Have a life span of 60 years when used as part of the structure, however it is accepted that materials that are not an integral part of the structure may require maintenance and or replacement within this period.

Building Regulation Requirements The requirements of Approved Document H, of the Building Regulations 2013 should be followed, and all relevant approvals sought from the Building Control Body. Where calculations are required to support the proposed design, these should be produced by a suitably competent and qualified person and made available for the approval of ICW. All the drainage must be constructed in a manner that ensures that all foul and surface water can be adequately moved to an appropriate final discharge. This must be done so that there are no effects on the structural stability of the building, the products used are fit for purpose and installed as per manufacturer’s details. They are robust and durable and be airtight to ensure hazardous materials and vermin do not enter the system.

Design Where a specialist design is requested or required, they shall: •

Be designed by a suitably qualified person.

•

Be supplied with clear precise instructions.

•

Be supported with structural calculation when outside the guidance of the Approved Documents.

Workmanship During the construction phase: •

All workmanship must be completed in a competent workmanship like manner.

•

Protected against unnecessary damage.

•

Design and Installation specifications are followed.

•

Products and materials are inspected for suitability for their purpose.

6.1 Excavations Basic Requirements All drainage must be constructed in a manner that ensures that all foul and surface water can be adequately moved to an appropriate final discharge. This must be done so that there is no effects on the structural stability of the building, the products used are fit for purpose and installed as per manufacturerâ&#x20AC;&#x2122;s details. They are robust and durable and be airtight to ensure hazardous materials and vermin do not enter the system. Throughout the installation the drainage must always be protected, and damage caused by site traffic is to be avoided at all costs.

During Excavation Drains should be excavated so that they will not be affected by the loading of the foundations, therefore the bottom of the drainage trench should not be lower than that of the foundation, where this situation in unavoidable then the drainage should be re-routed to create separation. Trenches should not be open for extended periods in advance of pipe laying and should be backfilled as soon as possible. It is essential that the sides of the trench are adequately supported during pipe laying. Trench widths should be as narrow as is practicable but not less than the pipe diameter plus 300mm to allow adequate side fill to be placed. Deeper excavations should ideally incorporate a sub-trench in accordance with the adjacent diagram.

6.2 Access and Connection Inspection Chambers and Rodding Facilities Access is required to drainage installations for testing, inspection and removal of debris. At all times there should be access and this is achieved by ensuring that each change of direction a suitable inspection chamber is installed and at each pipe end a suitable facility to rod pipes should be installed.

As rodding eyes provide access for clearance of debris in the direction of flow only and they should always be used in conjunction with an access chamber or manhole at a point downstream. No part of the drain or sewer should be more than 50m away from a manhole. The distance between points should therefore not exceed 100m, guidance should always be made to BS EN 752.

Internal sizes Type

Depth to invert from cover level (mm) Length x Width (mm)

Rodding eye

Small access fitting

Cover sizes

0mm

Circular (mm)

Length x Width (mm)

As drain with min. 100

150 dia 150 x 150

Circular (mm)

Same as pipework

150 x 100

150

150 x 100

Same size as access fitting

225 x 100

225

225 x 100

Same size as access fitting

0.6 or less

225 x 100

190

1.2 or less

450 x 450

450

Min. 430 x 430

430

Greater than 1.2

450 x 450

450

Max. 300 x 100

Access restricted to max. 350

0.6 or less, except where situated in a chamber Large access fitting

225 x 100

190

Shall inspection chamber

Deep inspection chamber

Larger opening cover can be used with restricted access for health and safety

Drains up to 150mm

Opening can be reduced by 20mm to support cover

6.2

Min Internal Dimensions Type

Manhole up to 1.5m deep to soffit

Manhole greater than 1.5m to soffit

Manhole shaft greater than 3m deep to soffit pipe

Size of Largest Pipe (DN) (mm)

Min Clear Opening Size

Rectangular length x width (mm)

Circular diameter (mm)

Rectangular length x width (mm)

Circular Diameter (mm)

150 or less

750 x 675

1000

750 x 675

N/A

225

1200 x 675

1200

1200 x 675

300

1200 x 750

1200

Greater than 300

1800 x DN+450

DN+450 or 1800 (whichever is the largest)

225 or less

1200 x 1000

1200

300

1200 x 1075

1200

375 - 450

1350 x 1225

1200

Greater than 450

1800 x DN+775

DN+775 or 1800 (whichever is the largest)

Steps

1050 x 800

Winch Ladder

600 x 600

600

1050

600 x 600

600

900 x 800

900

600 x 600

600

1200 x 800

1200

6.3 Connections Where half round channels are used in inspection chambers and manholes the branches up to and including 1500mm diameter should discharges into the channel in the direction of flow at or above the level of the horizontal diameter. A branch with a diameter >150mm should be set with the soffit level with that of the main drain. Where the angle of the branch is more than 45 degrees a three-quarter section branch should be used. Channels and branches should be benched up at least to the top of the outgoing pipe and at a slope of 1 in 12. The benching should be rounded at the channel with a radius of at least 25mm.

6.4 Gullies Gullies should always be provided where drives, paths and hard standings with impervious surfaces drain into a rainwater system. Gullies should be levelled with the correct bedding material. Hard materials should not be used as temporary support to achieve gradients as the can create hard spots which can distort the finished pipe runs.

6.5 Bedding Material Granular material for bed & surround of uPVC drains and sewers should comply with the requirements of BS EN 13242.

Pipe size

Bedding in accordance with BS EN 13242

Flexible 110mm/ Rigid 100mm

Bedding gravel 4/10mm

Flexible 160mm/ Rigid 150mm

Bedding gravel 2/14mm

6.6 Backfill Material It is acceptable that material excavated as part of the initial excavation will be deemed suitable if it is free from the following:

It is advisable that backfill material should be compacted in 300mm layers, care should be taken when using compaction equipment.

•

Boulders

Pipes for drainage should comply with the following British Standards:

•

Building rubble

•

BS 4962 – Plastic pipes

•

Timber

•

BS 1194 – Concrete porous pipes

•

Plastic

•

BS 65 or BS 1196 – Clayware pipes

•

Vegetable matter

•

Contaminants

6.7 Flexible Pipes

Class D: Bedding Factor 1.1

Class N: Bedding Factor 1.1

Where accurate hand trimming is not possible Class N is an alternative to class D.

6.8 Drainage Systems Combined Systems of Drainage

Foul Water Drainage System

In some instances, especially on older properties there may be instances where the surface water and foul water systems are combined.

Any foul water taken from a sink, bath, shower, toilet, washing machine or dishwasher is deemed to be foul water and should be disposed of in accordance of the requirements of Approved Document H of the Building Regulations. Foul water must be treated where surface water does not so the requirements differ in that the local water authority will treat this water at a designated treatment works.

Paragraph 3.5 of Approved Document H3 states that: Some sewers carry both foul water and surface water (combined systems) in the same pipe. Where they do the sewerage undertaker can allow surface water to discharge into the system if the sewer has enough capacity to take the added flow (see Approved Document H1 paragraph 2.1). Some private sewers (drains serving more than one building that have not been adopted by the sewerage undertaker) also carry both foul water and surface water. If a sewer operated as a combined system does not have enough capacity, the surface water should be run in a separate system with its own outfall.

Soakaways The Building Regulations Approved Document H places the list of priority for the discharge of surface water firstly by means of a soakaway. The process of soakaway design should be designed by a competent person and guidance used in BRE 365 Soakaway design should be adopted. The ground conditions have a significant impact on whether the water can permeate into the strata and in some instances, this may not be the case. In general, as site that is deemed to be suitable would have the following: •

Be lower than the area being drained, i.e. have sufficient falls.

•

Be located at least 5m away from the habitable part of the building: Approved Document H.

•

Located away from the foundations.

•

A design that complies with BRE 365.

•

Be situated so that there is no risk of contamination from pollutants.

Septic Tank Systems, Treatment Plants, Cesspits It is common especially in rural locations that mains sewerage is not present, and the use of a water treatment or cesspool is required. There are a variety of systems that can be used and installed to differing levels of capacity and outfall requirements. It is advisable that as a minimum the guidance found in Approved Document H (H2) is followed. In some instances, you may need environment agency consent to discharge and the necessary approvals should be sought prior to installation.

6.9 Above Ground Drainage All roofs will require the provision of gutters and falls pipes which should be installed as per manufacturerâ&#x20AC;&#x2122;s instructions and flow rates should be calculated to ensure the free flow of water movement. Sizes and dimensions should follow the guidance of Approved Document H and the table below:

Max Effective Roof Area (m2)

Gutter Size (mm dia)

RWP Outlet Size (mm dia)

Flow capacity (ltr/sec)

0.38

100

0.78

115

1.11

125

1.37

103

150

2.16

Above Ground Drainage Within the fabric of the building there will be various drainage systems to accommodate the free flow of water to the below ground system. All of this drainage must be designed and installed to the manufacturerâ&#x20AC;&#x2122;s standards and specifications All above ground plumbing systems need to be designed to allow the unobstructed flow of wastewater from an appliance to the underground drainage system.

6.10 Drainage Layout The layout of the drainage system should be kept simple. Changes of direction and gradient should be minimised and as easy as practicable. Access points should be provided only if blockages could not be cleared without them. The below bullet points refer to paragraphs taken from Approved Document H and should always be followed. •

Connection of drains to other drains or private or public sewers, and of private sewers to public sewers should be made obliquely, or in the direction of flow.

•

Connections should be made using prefabricated components. Where holes are cut in pipes a drilling device should be used to avoid damaging the pipe.

•

Where connections made to existing drains or sewers involve removal of pipes and insertion of a junction, repair couplings should be used to ensure a watertight joint and the junction should be carefully packed to avoid differential settlement with adjacent pipes.

•

Sewers (serving more than one property) should be kept as far as is practicable away from the point on a building where a future extension is likely (e.g. rear of a house, or side of house where there is room for a side extension). The system should be ventilated by a flow of air. A ventilating pipe should be provided at or near the head of each main drain. An open ventilating pipe (without an air admittance valve) should be provided on any drain fitted with an intercepting trap (particularly on a sealed system), and on any drain subject to surcharge. Ventilated discharge stacks may be used. Ventilating pipes should not finish near openings in buildings.

•

Pipes should be laid to even gradients and any change of gradient should be combined with an access point

•

Pipes should also be laid in straight lines where practicable but may be laid to slight curves if these can still be cleared of blockages. Any bends should be limited to positions in or close to inspection chambers or manholes and to the foot of discharge and ventilating stacks. Bends should have as large a radius as practicable.

Appliance

Max no. to be connected

Max. length of branch pipe (m)

Min. size of pipe (mm)

Gradient limits (mm fall per metre)

WC outlet >80mm

100

18 to 90

WC outlet <80mm

18 to 90

Urinal - Bowl

18 to 90

Urinal - Trough

18 to 90

Urinal - Trough

31 1.7

18 to 22

1.1

18 to 44

0.7

18 to 87

18 to 44

Washbasin or bidet

Should be as short possible to prevent deposition

Not recommended where disposal of sanitary towels may take place via the WC

May be reduced to 9mm on long drain runs, where space is restricted, but only if more than 1 WC is connected

6.11 Ventilation Within or external to the building there will be a need to provide a means of ventilation to the drainage system.

Air Admittance Valves Where air admittance valves are used to terminate soil pipes, they should comply with the Building Regulations Approved Document H. Valves within the building should be: •

Positioned in areas which are not liable to freezing.

•

Positioned in areas which have adequate ventilation.

•

Accessible for maintenance.

When air admittance valves are installed within the loft space the valve should be: •

Installed vertically.

•

Installed 150mm above the insulation level.

Venting to Atmosphere •

Ventilating pipes open to outside air should finish at least 900mm above any opening into the building within 3m and should be finished with a wire cage or other perforated cover, fixed to the end of the ventilating pipe.

•

A ventilating pipe should be provided at or near the head of each main drain. An open ventilating pipe (without an air admittance valve).

If the discharge stack provides the only ventilation to septic tanks or cesspits, the connecting drain is subject to periodic surcharging or is fitted with intercepting traps, air admittance valves are not suitable ventilation.

6.12 Testing Flow must be maintained from all plumbing systems and guidance found in Approved Document H of the Building Regulations should be implemented as a minimum standard.

Flow rates

Flow Rates from Dwellings

The unobstructed flow of waste in all above ground plumbing systems will be allowed from an appliance to the underground drainage. This will be achieved by following the notes below at design and installation stages: •

Pipe and gutter sizes are adequate to take the expected rate of discharge and are laid at suitable gradients with the minimum of direction changes.

No of dwellings

Flow rate (ltr/sec)

2.5

3.5

4.1

4.6

•

75mm deep seal traps should always be used except on a WC or where an appliance on the above ground drainage system.

•

Pipe sizes should not exceed the dimensions for diameter against pipe length;

•

Pipe sizes should be laid at a gradient of 1/80 or better.

5.1

•

Venting to the external wall at the highest point of a drainage system (head of run).

5.4

•

At the head of underground drains ventilation is to be provided. Either by a soil pipe, or a separate ventilation pipe.

5.8

•

A soil or ventilation pipe should extend at least 900mm above an opening if it is less than 3m away from an opening into the building.

Testing of Drainage •

Fill drainage pipes and leave for a one-hour period then release the bungs to inspect flow.

•

The test pressure should then be maintained for a period of 30 minutes, by topping up the water level as necessary so that it is within 100mm of the required level throughout the test. The losses per square metre of surface area should not exceed 0.15 litres for test lengths with only pipelines or 0.20 litres for test lengths including pipelines and manholes, or 0.40 litres for tests with only manholes and inspection chambers alone.

Ground Floor

7.0 Ground Floor Statutory Requirements

Materials

Roles and Responsibilities

All materials used shall:

When considering ground floor design this should be linked directly to the site investigation report. It is the responsibility of the developer to ensure the correct ground floor is provided and inspected.

•

Be adequately protected and stored in a correct manner.

•

Comply with relevant British Standards or equivalent European Technical Specification with the certification available for inspection by ICW.

•

Be installed as per Manufacturers details.

•

Building Regulations The requirements of Approved Documents of the Building Regulations 2013 should be followed, and relevant approvals sought from the Building Control Body. Any ground bearing floor construction which requires structural engineer’s details should be sought prior to the installation of the floor. The design should ensure that the structural integrity meets the requirements needed to safely distribute loads to the foundations and the ground. Any contamination, including gases, sulphates etc. should be identified at the site investigation stage and appropriate measures taken to address these issues.

Design Where a specialist design is requested or required, they shall: •

Be designed by a suitably qualified person.

•

Be supplied with clear precise instructions.

•

Be supported with structural calculation when outside the guidance of the Approved Documents.

•

Be available for inspection by ICW

Workmanship During the construction phase: •

All workmanship must be completed in a competent workmanship like manner.

•

Protected against unnecessary damage.

•

Design and Installation specifications are followed.

•

Products and materials are inspected for suitability for their purpose.

7.1 Ground Bearing Floor Slabs All topsoil including organic material, tree roots and vegetation shall be removed prior to construction of the slab. The hardcore should be certified fit for purpose and compacted no greater than 5 times its nominal value. Appropriate compaction equipment should be used.

Damp-Proof Membrane Above Slab

Insulation Below Slab

Damp-Proof Membrane Above Slab

There should be an adequate Damp Proof Membrane installed and guidance found in Approved Document C: Diagram 4 and Technical solution in paragraph 4.7 followed. Where reinforcement is required suitable structural details should be provided as part of the floor design by a suitably qualified person.

7.2 Precast Beam & Block Floors Precast Beam & Block Floors Any details of precast floors including beam and block should always be provided prior to installation and the manufacturer’s installation technique followed. Any walls supporting the precast beam and block floor should be suitably designed by a competent person and designed to adequately support the loads. Guidance can be found in Approved Document C, Technical Solution Paragraph 4.18. Cross ventilation should also be provided to the void beneath the beam and block floor, and a minimum void depth of 150mm should be provided below the underside of the floor structure to the top of the ground level. When installing block and beam suspended floors ensure: •

Joist are located above DPC level.

•

Min 150mm gap is provided between underside of joist and oversite.

•

Air bricks are a min of 75mm above ground level.

•

Beams are bearing on to the inner leaf of the cavity wall and do not project into the cavity.

•

Installed as per manufacturers details.

7.3 Suspended Timber Floors Any walls supporting the timber floor should be suitably designed by a competent person and designed to adequately support the loads. A suitable concrete oversite should be provided beneath all suspended timber floors. It is recommended that guidance found in Approved Document C: Technical Solution 4.14 is followed. Cross ventilation should be provided to the void beneath the timber floor, and there should always be a minimum void depth of 150mm below the underside of the floor structure to the top of the ground level. Depending on the proposed floor finish, the chipboard, OSB or tongued and grooved floorboards are all suitable materials, subject to loading requirements. And all the flooring types should be adequately fixed, preferably by screws. When installing timber suspended floors ensure: •

Joist are located above DPC level.

•

Min 150mm gap is provided between underside of joist and oversite.

•

Air bricks are a min of 75mm above ground level.

•

Joists are bearing on to the inner leaf of the cavity wall and do not project into the cavity.

•

Joists are correctly sized.

•

Joist are adequately strutted.

7.4 Damp Proof Membranes It is recommended that all DPM’s should be a minimum of 1200 gauge, and laid on a sand blinding to prevent puncture, as shown in Approved Document C: Diagram 4. DPM’s should be provided to all ground bearing concrete slabs, reinforced concrete slabs, precast beam and block floors and to over sites of suspended timber floor structures. It is recommended that all DPM’s are continuous, however, often due to service installation this is not always possible, so it is recommended that where joints are created the joint is suitably sealed with appropriate tape. An additional layer may be required subject to the inspection of the inspector.

7.5 Radon Gas Barrier Radon is a colourless, odourless radioactive gas which is formed by the decay of uranium that naturally occurs in all rocks and soils. Radon is everywhere, although in many areas the levels are low, so present little danger to public health.

This example avoids creating a horizontal path through the wall. The step must be a minimum of 75mm.

Public Health England have prepared maps indicating the chance of a building having a high radon level. These maps cover England, Wales, Scotland and Northern Ireland. Even in the areas with the highest radon level, not all buildings will be deemed to have high levels. These maps can be viewed at www.ukradon.org. Radon enters a building via small gaps and cracks that are formed throughout the buildingâ&#x20AC;&#x2122;s life. The atmospheric pressure difference between the inside and outside causes the gases to be drawn up through the soil and into the building. Public Health England recommends that radon levels should be reduce in homes where the average is more than 200 becquerels per metre cubed (200 BQ m3). This recommendation has been endorsed by the government. This action level refers to the annual average concentration in a home. Radon measurements are carried out with two detectors (in a bedroom and living room) over three months (to average out the short-term fluctuations). Where radon has been found to exist, it is important to protect from its exposure. In order to do this, a radon barrier must be installed as part of the ground floor construction.

Avoiding jointing materials or stepped trays, it is possible to install the radon barrier as a single horizontal layer. The barrier is laid a minimum of 225mm below external ground level.

Super Structure

8.0 Superstructure Statutory Requirements

Materials

Roles and Responsibilities

All materials used shall:

When considering superstructure design this should be linked directly to the site investigation report. It is the responsibility of the developer to ensure the correct superstructure is provided and inspected.

•

Be adequately protected and stored in a correct manner.

•

Comply with relevant British Standards or equivalent European Technical Specification with the certification available for inspection by ICW.

•

Be installed as per Manufacturers details.

•

Building Regulations The requirements of the Approved Documents of the Building Regulations 2013 should be followed, always and all of the relevant approvals sought from the Building Control Body. If any calculations are required to support the proposed design, then these should be provided by a suitably competent and qualified person. The calculations will need to be designed so as they safely distribute loads and forces to the foundations.

Workmanship

Design Where a specialist design is requested or required, they shall: •

Be designed by a suitably qualified person.

•

Be supplied with clear precise instructions.

•

Be supported with structural calculation when outside the guidance of the Approved Documents.

•

Be available for inspection by ICW.

During the construction phase: •

All workmanship must be completed in a competent workmanship like manner.

•

Protected against unnecessary damage.

•

Design and Installation specifications are followed.

•

Products and materials are inspected for suitability for their purpose.

8.1 Exposure The country can be divided into areas rated as sheltered, moderate, severe and very severe exposure to wind driven rain based on extensive metrological studies. There is a link between high exposure areas and the likelihood of brickwork suffering the consequences of frost attack if design, detailing and construction have not been properly addressed. All areas within 8km of the coast and major river estuaries should be considered as being one â&#x20AC;&#x2DC;gradeâ&#x20AC;&#x2122; of exposure higher than that indicated on the map. The same applies to high buildings or buildings on high ground. The degrees of exposure will also depend on the position of the brickwork in the building or structure and the way in which the detail has been designed. Generally external works such as retaining walls, garden walls and copings, and building features such as sloping areas, parapets, sills and areas between ground level and DPC are subject to more severe exposure than the rest of the building. This coupled with the geographical location classed as severe or very severe must be designed and constructed with due consideration.

8.2 Bricks BS EN 771 classifies bricks in accordance with their durability designation, In selecting the correct brick it is important to consider the exposure their will face and their location within the structure if in doubt then the standard classification F1,S2 or F1,S1 should be used below and 150mm above the DPC.

Wall height

Minimum compressive strength of brick or block unit Block

2.9N/mm

Block

9N/mm

Block

7.5N/mm

Block

13N/mm

Block

2.8N/mm

Block

9N/mm

One to two storeys

Lowest storey of a three-storey wall or where individual storeys exceed 2.7m

Upper storeys of a three-storey wall

8.3 Blocks Blocks should meet BS EN 771 and have a minimum density of 1500Kg/m2 with a minimum compressive strength of 7.3N/mm2

8.4 Masonry Protection It is advisable that all new masonry should be protected by covering, to ensure that the walls are not saturated by rainwater, or they do not dry out too quickly especially in hot weather. Consideration must also be given in the winter months when we experience reduced temperatures due to frost. Masonry should not be laid in poor weather or temperatures below 2 degrees. Insulated boards or heaters may be considered in extreme weather conditions.

Material Suitability All bricks and blocks must have a suitable level of durability and particular attention should be paid to the brickâ&#x20AC;&#x2122;s resistance to frost and moisture and comply fully with BS EN 771â&#x20AC;&#x201C;1

Non-Rendered Blockwork All external blockwork should be rendered or otherwise finished with a cladding that is appropriately durable, unless the block manufacturer can provide third party certification confirming that the blockwork can be left unfinished or finished in an alternative way. Approved Document C: Technical Solution 5.9 (b).

8.5 Mortars Mortar joints are vulnerable to frost failure and general weathering and may require increased maintenance in regions rated as severe exposure to wind driven rain.

Location

Mix Proportions

Aggregate Blocks

Airtec Blocks

Clay Brick

Cement:

1 : 1: 5-6

1:2:9 or 1 : 1 : 6

1:1:5

Mortar is an essential ingredient of brickwork and is subject to the same exposure as the brick.

Mortar General All mortars should be fit for purpose and comply with all relevant standards, it is advisable to utilise manufacturer’s guidance. The mixing of the mortar should be continuous to ensure consistency and quality, hand mixing is not recommended, and all mortar should be mixed in a mechanical mixer.

Above DPC

Cement: Sand (with plasticiser)

1 : 5-6

1:6

1:4

Masonry Cement: Sand

1 : 4-5

1:5

1:3

Notes

Grade iii mortar or iv mortar as per BS 5628-2.

8.6 General Advice on Cavity Walls A traditional masonry wall should be constructed using an inner and outer leaf and a cavity should be provided:

•

Both walls should be tied together using wall ties using guidance in Approved Document A Paragraph 2C8.

•

In general, the current minimum dimensions for cavities is 100mm subject to SAP.

•

The cavity should be kept clear from mortar to ensure there is no bridging.

Insulation of the cavity can be full or partial fill depending on exposure to wind driven rain. For partial fill insulation, a minimum clear cavity of 50mm should always be provided as Approved Document C: paragraph 5.15. 84

8.7 Solid Wall

Internal Insulation

External Insulation

8.8 Cavity Wall

Partial Fill Insulation

Full Fill Insulation

8.9 Framed Walls

Timber Framed Wall with Brick Cladding

Timber Framed Wall with Tile Cladding

8.10 Lateral Restraint Wall Restraint All the walls should be restrained adequately in accordance with the Building Regulations Approved Document A, and there are a variety of restraint methods can be used. It is advisable to see manufacturer’s details when using restraints and their fixings. Restraint can be provided by: •

Joist hangers.

•

Lateral restraint straps.

•

Wall Ties.

When installing joist hangers it is important to ensure that the hanger is bedded directly on the masonry and there is no gap between the hanger back-plate and the face of the masonry, there should be at least 450mm of masonry provided above the hanger and the hanger is spaced subject to the correct centres of timber specification as shown in TRADA table spans.

Joist hangers are suitable for and can be used with connections between wood-based members such as: •

Structural solid timber classified to C14-C40 according to EN 338 / EN 14081.

•

Glulam classified to GL24-GL36 according to EN1194 / EN 14080.

•

LVL according to EN 14374.

•

Parallam PSL.

•

Intrallam LSL.

•

Duo- and Triobalken.

•

Layered wood plates.

•

I-beams with backer blocks on both sides of the web in the header and web stiffeners in the joist.

•

Plywood according to EN 636.

8.11 Lateral Restraint Straps Floors should provide lateral restraint to all walls running parallel to them, by means of 30mm x 5mm galvanized or stainless-steel restraint straps at 2m centres. Further guidance can be found in Approved Document A.

8.12 Wall Ties Wall ties will be adequate if they meet the following provision: •

They are to BS EN 845-1.

•

They should be appropriate for the width of cavity and have at least 50mm bearing on each leaf.

•

To be laid to a slight fall towards the outer leaf and have the ability to hold insulation against an internal leaf for partial fill scenarios.

•

Stainless steel wall ties should always be used.

It is important to note that only BS EN 845-1 type wall ties or specifically manufactured and tested.

8.13 Cavity Closers Suitable cavity closers should be installed to all door and window openings and the manufacturers installation guide should always be adhered to. Guidance followed In Approved Document C: diagram 13 gives visual guidance of cavity closers in cavity walls Checked rebate.

8.14 Movement Joints Movement in Masonry Vertical movement joints should be provided to the outer leaf of cavity walls as indicated in Table below. The first joint from a return should be no more than half the dimension indicated in the table. Movement joints below the DPC should also be provided at major changes in foundation level and at changes in foundation design. Wall ties at a maximum of 300mm centres should be provided each side of movement joints. Compressible filler such as polyurethane foam should be used to form the joint and be sealed to prevent water penetration. Fibreboard or cork are not acceptable materials for forming movement joints in masonry.

Expansion Joint Spacings Material

Normal Spacing

Joint Thickness

Clay Brickwork

12m (spacing up to 15m may be possible if sufficient restraint is provided â&#x20AC;&#x201C; consult Designer)

15mm

Calcium Silicate and Concrete Brickwork

7.5 â&#x20AC;&#x201C; 9m

10mm

Concrete Blockwork (used in outer leaf)

10mm

Stone

12m

15mm

Elastic sealants (Type E) are suitable as they allow for reversible movement. Note: It is not normally necessary to provide movement joints to the internal leaf of cavity walls but should be considered where rooms occur with unbroken lengths of wall in excess of 6m. The first joint from a return should be not more than half the dimension indicated in the table. Movement joints are not acceptable in solid party or separating walls; however, where cavity wall construction is adopted, offset movement joints with a solid rubber compressible strip may be acceptable.

8.15 Structural Openings Beams and Lintels Beams and lintels must be fit for purpose and designed for the loads they will be subject to. They should be installed as per manufacturers details and have suitable end bearing. For guidance generally lintels up to 1.2 meters will require an end bearing of 100mm and lintels over 1.2 meters will require an end bearing of 150mm minimum. There are a variety of lintels which are acceptable and will take the form of concrete, steel or timber. However, the lintel must be fit for purpose and meet the structural requirements of its intended purpose.

Minimum Lintel Bearings (mm) Opening Dimension (mm)

Lintel Bearing

<1.2

100 mm

>1.2

150 mm

Lintels When installing lintels, it is recommended that the installation guidance of the manufacturer is always followed and that all lintels are deemed fit for purpose and are correctly insulated, having sufficient moisture resistance, structural integrity and meet the requirements of the relevant Approved Documents.

8.16 Cavity Trays and DPC’s Cavity Trays

Weep-Holes

The purpose of cavity trays, weep-holes and stop ends is to prevent the build-up of water within a cavity wall and allow the water to escape through the outer leaf. This can be caused by precipitation or condensation building up within the cavity. Additional guidance and pacing of cavity trays can be found in Approved Document C: Technical solution 5.9 (d). It is advisable that cavity trays are installed in the following situations:

Weep-holes must be installed at no more than 450mm centres and generally have the following characteristics. •

A full height plastics wall weep which corresponds to the height of a standard brick. Incorporates an integral insect guard and wind baffle.

•

Provides the maximum clear opening in the mortar joint with no restrictions.

•

Above cavity insulation which is not taken to the top of the wall, unless that area of wall is protected by impervious cladding.

•

Above rectangular ducts, lintels and recessed meter boxes .

Stop-Ends

•

Above lintels in walls in exposure zones 4 and 3 and in zones 2 and 1.

•

Continuously above lintels where openings are separated by short piers.

•

Above openings where the lintel supports a brick soldier course.

When installing cavity trays there should always be a watertight stop-ends to prevent moisture entering the cavity. These stop ends must be bonded to the cavity tray. Normally the stop-end is located to coincide with the nearest perpend to the end of the cavity tray. Stop-ends can be formed by sufficiently turning up the end of a DPC tray into the perpend joint. There should be no mortar build up within the cavity or near to the stop ends

8.17 Floor Joists Timber Floor Joists

Engineered I-Joists

All floor joists should be correctly sized and graded as per the guidance found in TRADA Span Tables (Eurocode 5)

Engineered I-joist are a cost-effective alternative to standard timber and do not require any drilling due to the open web system.

It is recommended that joists are placed on joist hangers to prevent and distortion through forces such as torsion. The joist should never be overloaded whilst construction is in process and guidance found in TRADA Span Tables (Eurocode 5) provides suitable loading figures per m2.

Pre-Cast Beam and Block Floors

Any joist that is adjacent to an opening such as a staircase should be doubled up and fixed adequately as per structural engineers’ detail, this may take the form of bolting together.

Pre-cast beam and block floors are an alternative to timber and can span excellent distances. If using this form the installation method must be as manufacturer’s details and the masonry supporting the beam will be calculated accordingly to ensure the forces and loads applied are transferred through the structure into the foundations. The blocks should be grouted together with a 1:6 cement / sand mix in accordance with the manufacturer’s instructions.

I-Joists I-joists and metal web trimmed joists are acceptable flooring joists and must meet the structural requirements calculated by the competent person. These joists can be installed using joist hangers or walled in ensuring 90mm bearing is achieved.

8.18 Notching and Drilling Notching and Drilling of Joists Joists can be notched providing it is in accordance with reference in TRADA detail below:

Reference can be made to tables 2.17 and 2.18 which translates diagram 2.108 drilling and notching zones into actual dimensions for a number of typical depths and spans. â&#x20AC;˘

Adjacent holes must not be closer than 3 times the diameter of the largest hole permitted.

â&#x20AC;˘

A notch and a hole within the same joist must be at least 100mm apart measured horizontally along the centre of the joist.

â&#x20AC;˘

Where the joist depth is greater than 250mm, then the dimensions of the shaded zones given in diagram 2.108 should be calculated using d = 250mm.

Depth of Joist *d* (mm)

Max. Depth of Notch 0.125d (mm)

Max. Diameter of Holes 0.25D (mm)

Min. Distance between Holes* (mm)

100

12.5

125

150

37.5

112.5

175

132

200

150

225

168

250

62.5

187.5

Notes: * distance given is when using maximum permissable hole size. If the joist depth is greater than 250mm, notch and hole sizes should not exceed those given for 250mm deep joist. If the joist depth is greater than 250mm, notch and hole sizes should not exceed those given for 250mm deep joists.

8.18

Holes to be drilled only within the zones A-B (distance given is taken from either supporting walls in mm)

Notches to be taken out only within the zones C-D (distance given is taken from either supporting wall in mm)

1.5

375

600

105

375

2.0

500

800

140

500

2.5

625

1000

175

625

3.0

750

1200

210

750

3.50

875

1400

245

875

4.00

1000

1600

280

1000

4.50

1125

1800

315

1125

5.00

1250

2000

350

1250

5.50

1375

2200

385

1375

6.00

1500

2400

420

1500

Clear Span of Joist* (mm)

Notes: *Clear Span is the distance between supports A = 0.25 x clear span B = 0.40 x clear span C = 0.07 x clear span

D = 0.25 x clear span

8.19 Floor Decking Floor Boarding

Softwood Floor Boarding - Minimum Thickness & Centres of Support

If floor boarding is used the following is acceptable: Tongue and grooved softwood flooring with a minimum moisture content at the time of fixing to be between 16-20% and be in accordance with BS 1297. All boards must be nailed or screwed adequately, and the minimum thickness can be seen in Table.

8.20 Particle Boarding Particle boards that are suitable for flooring are oriented strand board (OSB) or chipboard. If using chipboard this should be tongue and grooved and all joints glued and installed to the correct manufacturerâ&#x20AC;&#x2122;s details. It is advisable that all boards are mechanically fixed by screwing or nailing at 250mm centres. Where the board abuts the perimeter wall an allowance of 10mm should be made for expansion.

Particle Floor Boarding - Minimum Thickness & Centres of Support Thickness (mm), Chipboard

Thickness (mm) OSB

Max Span

Typical Nail Fixing (mm)

18 and 19

450

60mm annular ring shank

18 and 19

600

65mm annular ring shank

Finished Board Thickness (mm)

Maximum Joist Centres

Typical Nail Fixing

450

45mm lost head nail

600

60mm lost head nail

8.21 Staircases Stairways The stairway should comply with Approved Document K of the Building Regulations in relation to the following: •

The pitch of the stair is to be no greater than 42°.

•

To have a maximum rise of 220mm with a minimum going of 220mm.

•

Headroom to be a minimum of 2m.

•

The handrail should be placed 900mm to 1000mm from the pitch line.

•

At its narrowest point, the minimum width of a winder tread should be no less than 50mm.

•

The spindles from spindle to spindle must be no greater than 99mm.

•

If glass is used this should meet the requirement of BS6206.

Type of Stairs

Maximum Rise (mm)

Minimum Going (mm)

Private Stairs

220

Access Stairs

190

250

Common Stairs

190

250

8.22 Internal Walls Internal Masonry Walls Foundations

Minimum Compressive Strength of Masonry Wall Height

Minimum Compressive Strength of Brick or Block Unit

All load bearing internal masonry walls shall be constructed with a suitable foundation. Block

2.9N/mm2

Brick

9N/mm2

Block

7.5N/mm2

Brick

13N/mm2

Block

2.8N/mm2

Brick

9N/mm2

One to two Storey

Compressive Strength There are endless brick and block strengths with various levels of durability but as a minimum the adjacent table will provide a suitable level of structural strength, for the height of the proposed building.

Lowest storey of a three storey wall or where individual storeys exceed 2.7m

Upper storeys of three storey wall

Bonding and Tying Bonding or tying an external wall to an internal wall is acceptable if a separating wall abuts an external wall they may be tied or bonded together if formed by using wall ties, an expanded metal strip, or equivalent fixings, at maximum 300mm vertical centres. It is recommended that the builder follows the technical guidance produced by the manufacturer and complies fully with the installation technique.

8.22

Wall Ties for Cavity Separating Walls

Partition Walls on Flooring Systems

To ensure structural stability the two leaves of the cavity wall should be tied together following guidance in Approved Document A. Wall ties for timber structures should be installed in accordance with the system designer’s recommendations for timber framed separating walls.

If partition walls are to be placed on the ground floor the floor must be designed to ensure that the additional weight can be suitably distributed. In the case of masonry this may require a foundation or thickening of the floor slab. In timber the sole plate must be adequately fixed to limit movement, each ground floor wall should have a DPC installed.

Load-Bearing Timber Walls and Partitions Any timber wall which is load bearing and forms part of the buildings structure shall be designed to ensure that the forces and loads applied to them are transferred through to the foundations. The wall shall be designed by a competent person and all structural timber shall be graded to strength class C16 or C24.

On first floor systems the timber boarding material shall be adequately fixed as per manufactures details and the wall placed to ensure that there is no movement. Extra noggins or joists should be specified where stud partitions or proprietary plasterboard partitions are supported by a timber floor. There should also be some allowance for deflection of the floors at the head of partitions and it is recommended that these are mechanically fixed with screws.

Partition walls in buildings are acceptable and can be formed from timber, steel or masonry. If these walls are structural, they must be pre-calculated by a competent person and have the necessary load bearing capacity, sound and fire resistance to carry out its function safely. Timber walls separating WC’s should have enough sound insulation applied within the studs.

Non Load-Bearing Timber Partitions All non-load bearing partitions should be constructed in accordance with the requirement of regulation 7 of the manual to the building regulations by ensuring workmanship and quality is achieved, the wall should have sufficient bracing and strength and should achieve the following tolerances: •

The tolerance of horizontal straightness of a partition should be +/- 10mm over a 5m length;

•

The deviation in vertical alignment of a partition in any storey height should be +/- 10mm;

100

8.23 Fire Resistance In dwellings 1/2 and 1 hours fire resistance should be achieved as a minimum, and the table below provides advice on how to achieve this requirement.

Fire Resistant Wall Specifications Material

1/2 hour FR

1 hour FR

Brick

90mm Thickness

Block

90mm Thickness

Plasterboard on Timber

12.5 board on both sides of frame

Two layers of 12.5mm board on both sides of framing or Proprietary fire boards (typically, 12.5mm-15mm) on both sides of framing

Plasterboard Laminated Wall

12.5mm laminated on both sidesof 19mm board

Refer to manufacturerâ&#x20AC;&#x2122;s recommendations

101

8.24 Sound Insulation There is a requirement of Approved Document E ‘Resistance to the passage of sound’, that certain walls within the dwelling must meet the minimum standard of sound resistance. Walls and floors separating a WC must have the correct sound resistance. This can be achieved by the installation of mineral wool placed within the floor void and studs.

Internal Wall Type A – Timber or Metal framed

Internal Wall Type B – Timber or Metal framed

Internal Wall Type C – Concrete Block Wall

Internal Wall Type D – Aircrete Block Wall

All separating walls in England and Wales may be built in accordance with Robust Details or Part E of the Building Regulations. Sound insulation can be complied with by using either:

102

8.25 Pre-Completion Testing Pre -completion testing is required in the following situations: •

To all new build domestic properties (including rooms for residential purposes).

•

Where the sound insulation construction is in accordance with the guidance given in Approved Documents of the Building Regulations.

8.26 Robust Details As an alternative, builders can register with Robust details and construct to their specification and eliminate the need for pre-completion testing. Robust Details Limited Block E Bletchley Park Science and Innovation Centre Milton Keynes Buckinghamshire MK3 6EB www.robustdetails.com

103

•

Where the building is not built in accordance with the Approved Documents of the Building Regulations.

•

The requirements of the Robust Details system have not been met.

8.27 Chimneys If a chimney is not provided with adequate support by ties or securely restrained, its height (measured to the top of the chimney) should not exceed 4.5 x its least horizontal dimension, when measured from the highest point of intersection with the roof surface (density of masonry must be minimum 1500kg/m3 (see diagram below).

Chimneys and Flues Ensure that all gas flues terminate to the open air i.e.. Flue blocks must terminate at an appropriate ridge vent or similar even where no appliance is fitted prior to the sale/ occupancy of the property.

Corrosion of Lead Work When free lime from mortar comes into contact with lead trays or flashings, (due mainly to the continual saturation of the brickwork) in areas such as chimneys, the lead should be protected from corrosion by the use of a thick coat of bitumen paint covering the faces likely to be in contact with the mortar. The protection against corrosion of lead work buried in mortar, is suggested in guidance given out by the Lead Sheet Association. This treatment can also reduce staining of lead and brickwork. It is unnecessary to treat flashings buried only 40 – 50mm into mortar joints (cover flashings), as this close to the drying surface carbonation of free lime is rapid and there is no risk of corrosion in such circumstances.

Special blocks are made to accommodate gas fire flues which tend to be slightly thicker than normal units. When used in external walls, care should be taken not to reduce the clear cavity width below 50mm. Typical chimney positions, dpc and flashing details are shown in diagrams adjacent Ensure that: •

A 50mm cavity at the back of the chimney breast is maintained to prevent rainwater penetration

•

Flue liners are used as specified with sockets upper most and jointed with fire resisting mortar

104

8.27

Chimney Tray, Low Level Required at low level where a cavity-walled chimney with brick shoulders is built on to an external wall; the tray prevents water which may enter the shoulders from penetrating to the inner leaf of the wall (see diagram below). Material: 1mm aluminium alloy sheet to BS EN 485-2: 1995 ‘Aluminium and aluminium alloys. Sheet strip and plate. Mechanical properties’. This has a higher melting point than lead, so is suitable for installation close to a heat source.

Chimney Tray, High Level Required to prevent the entry of water at high level where a chimney rises through a pitched roof; suitable for newbuild or remedial work. Minimises disturbance to surrounding construction in remedial work. Material: Lead sheet to BS 1178: 1982 ‘Specification for milled lead sheet for building purposes. Code 4 as standard. Standard sizes: 800 x 800mm, 900 x 900mm, 950 x 950mm. To suit either 195mm square or 195mm diameter circular flue.

105

Cladding

9.0 Introduction Wall cladding presents a hazard if it becomes detached from the building and may cause structural failure and water ingress. An acceptable level of safety can be achieved by different means depending on the type and location of the cladding. This relates to all forms of cladding, including curtain walling and glass facades. Further guidance on the acceptance and viability of wall claddings can be sought on the Building regulations for England & Wales, Scotland and N.Ireland, guidance concerning the weather resistance of wall cladding is included in Approved Documents, site preparation and resistance to moisture, or guidance on resistance to spread of fire, fire safety, or guidance in relation to sound insulation and resistance to the passage of sound.

Wind Loading

The cladding will meet the safety requirements if:

Fixings

•

The cladding is capable of safely sustaining and transmitting to the supporting structure of the building all dead, imposed and wind loads.

•

The cladding is securely fixed to and supported by the structure of the building. This shall comprise both vertical support and horizontal restraint.

The selection of fixings for supporting cladding should be fully compliant with the latest Buildings Regulations and fully compliant with the manufacturer’s installation guidelines and any third-party accreditation or approvals.

•

Provision is made, where necessary, to accommodate differential movement of the cladding and the supporting structure of the building.

•

The cladding and its fixings (including any support components) are of durable materials; the design life of the fixings being not less than that of the cladding. Fixings shall be corrosion resistant and of a material type appropriate for the local environment.

•

The cladding is resistant to penetrating and driving rain.

•

The cladding is resistant to fire spread as per the guidance noted.

Wind loading on the cladding should be derived from BS 6399, Part 2: 2001 with due consideration given to local increases in wind suction arising from funnelling of the wind through gaps between buildings. Guidance on funnelling effects is given in BRE Digest 436 Wind loading on buildings - Brief guidance for using BS 6399-2: 1997 available from BRE. Where the cladding is required to support other fixtures and fittings (e.g. handrails and antennae), account should be taken of the loads and forces arising from such fixtures and fittings.

106

9.1 Timber Boarding Timber boarding should be at least 16mm thick and allowance for moisture movement in boarding should be made by making tongues, joints or overlaps at least 10% of the board width. Timber boarding should be battened off the supporting background to provide a minimum 19mm cavity for draining and venting. Battens should be a minimum 38mm wide, preservative treated and at maximum 600mm centres. A breather membrane should always be installed when horizontal battens are located against the sheathing. Battens on timber frame should be fixed to each stud (and not to the sheathing) with annular ring nails of length at least twice the batten thickness plus the sheathing thickness (or plain shank nails of length 2.5 times the batten thickness plus the sheathing thickness). Boards should be fixed to battens by face or secret nailing annular ring nails at least twice the board thickness or plain shank nails at least 2.5 times the board thickness. Butt joints at board ends should occur at battens. Nails should be either hot dipped galvanised, stainless steel or equally durable. Aluminium nails should not be used with copper containing preservative treated timber and galvanised nails should not be used with western red cedar. Ends cut on site should be dipped or liberally brushed with preservatives. Claddings fixed directly to frame.

Avoid the following defects: •

Insufficient overhang of roof at verges to protect render.

•

Battens fixed directly to sheathing.

•

Mesh for render inadequately fixed to timber frame.

•

Mesh for render damaged or deformed.

•

Movement or slipping of timber cladding.

107

9.1

Timber and boards for exterior use should be of a durable species, with sapwood excluded, or preservative treated by pressure impregnation using preservatives suitable for use in hazard class 3 in compliance with BS8417:2003, or equivalent.

Hardwoods

Softwoods

Preservative Treatment

Afrormosia

Western Red Cedar

Not Required

Afzelia

Not Required

Iroko

Not Required

Keruing

Not Required

Mahogany, African

Not Required

Oak, European

Not Required

Opepe

Not Required

Sapele

Not Required

Teak

Not Required

Utile

Not Required

Abura

Douglas Fir

Required

Elm

Hemlock, Western

Required

Meranti

Larch, European

Required

Larch, Japanese

Required

Redwood (European) or Scots Pine

Required

Sitka Spruce

Required

Whitewood or European Spruce

Required

108

9.1

Plywoods European Birch or Birch Faced Plywood (WBP)

Required

European Softwood Plywood (WBP)

Required

North American Douglas Fir or Douglas Fir Faced Plywood (Exterior Grade)

Required

North American Softwood Plywood (Exterior Grade)

Required

Gabon or Mahogany Plywood (WPB)

Required

Marine grade plywood specified in accordance with BS 1088 but excluding Gabon

Not Required

Typical preservatives are those conforming to the requirements of BS EN 599-1:1997 for hazard class 3, for example micro emulsions or copper organic pressure impregnated.

109

Where timber boarding or plywood spans across an intermediate floor zone in timber frame construction, allow for differential movement caused through timber shrinkage, by incorporating a movement joint (see diagram below). Where cavity barriers are required, they should be correctly fitted without gaps, fill the cavity and be fixed with stainless steel staples or equally durable fixings. Abutments between cladding and other weather-resisting elements should be neatly made, be weather-tight and allow for differential movement (see diagram 2.104). Workmanship should comply with BS 8000:5.

9.2 Timber Boarding to be preservative treated, minimum 16mm thick and sufficient tongues or overlaps provided to permit shrinkage and expansion of the timber. Timber boarding should be battened off the sheathing to provide a minimum 19mm cavity for draining and venting. Battens should be a minimum 38mm wide, preservative treated or equivalent hazard class 2 and at maximum 600mm centres. Battens should be fixed to each stud (and not to sheathing) with annular ring nails of length at least twice the batten thickness plus the sheathing thickness or plain nails of length at least 2.5 times the batten thickness plus the sheathing thickness. All nails to be fixed at 600mm centres.

Counter Battens Should be Used for Vertical Cladding Boards should be fixed to battens by face or secret nailing with annular ring nails at least twice the board thickness or plain shank nails at least 2.5 times the board thickness. Butt joints at board ends should occur at battens. Nails should be either hot dipped galvanised, stainless steel or equally durable. Aluminium nails should not be used with copper containing preservative treated timber and galvanised nails should not be used with western red cedar.

110

9.3 Plywood Plywood sheets used as cladding should be pressure preservative treated, a minimum 12mm thick and bonded with WBP or equal quality exterior adhesive and marked accordingly. Battens should be vertical and treated. Joints between sheets should be made resistant to excessive water penetration by fixing cover battens or flashings.

9.4 Render onto Timber Cladding •

Battens should be either 25 x 38mm or 50 x 50mm, preservative treated. Battens should be fixed to each stud with annular ring nails of length at least twice the batten thickness plus the sheathing thickness or plain nails of length at least 2.5 times the batten thickness plus the sheathing thickness.

•

Horizontal battens must be drilled or notched to maintain ventilation requirements.

•

Nails should be hot dipped galvanised, stainless steel or equally durable.

•

Mesh or metal lathing should be stainless steel or assessed by an independent authority and fixed to vertical battens at maximum 600mm centres with stainless steel staples.

111

•

Laps in the lathing should be wired together at 150mm centres.

•

A damp-proof course should be provided between unbacked rendered lath and timber battens.

•

Render should not bridge the dpc and should be finished onto a durable render stop.

•

Three coat work is essential, at least 16mm thick.

•

First and second coats should be 1:1/2:4 (cement : lime : sand) or 1:3 (cement : sand with plasticiser) or 1:3 (masonry cement : sand).

•

Final coat should be 1:1:6 (cement : lime : sand) or 1:6 (cement : sand with plasticiser) or 1:41/2 (masonry cement : sand).

9.5 Tile and Slate Cladding •

Tile or slate cladding should be fixed in accordance with the manufacturer’s recommendations.

•

Battens should be a minimum 38 x 25mm for stud centres up to 600mm, and should be preservative treated (BS 8417, or equivalent, hazard class 2). 38 x 19mm counter battens should be provided on severely exposed sites. Severely exposed sites are those shown on the wind driven exposure map contained on page 161.

•

Battens should be level and fixed to each stud (not to sheathing) with annular ring nails of length at least twice the batten thickness plus sheathing thickness or plain nails of length at least 2.5 times the batten thickness plus the sheathing thickness.

•

Battens should not normally be less than 1200mm in length and span across at least 3 supports.

•

Nails should be either hot dipped galvanised, stainless steel or equally durable.

•

A breather membrane (not a roof underlay) should normally be fixed to the sheathing behind the battens.

•

Edge of hanging tiles should be cloaked at the jambs of all openings with purpose made corner tiles or by butting against a timber reveal with drainage channel behind.

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9.6 Other Claddings Other cladding should only be used if they either: •

Conform with a British Standard and, where appropriate, are detailed for use with timber frame construction by the manufacturer.

•

Approved as being suitable by an independent assessment authority.

•

In addition, they should be approved by International Construction Warranties Limited.

9.7 Weather Resistance of Walls and Cladding Existing solid brick or stone walls may be acceptable as a weather resisting wall subject to the exposure category of the building (see exposure to wind driven rain map) and the porosity of the masonry. It is anticipated that all buildings located in severe or very severe locations will require at least one of the additional treatments noted below. However, all solid masonry wall situations will require a specialist’s report to identify the extent of any necessary remedial treatment.

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The specialist report including the proposed design and/or the manufacturer’s details must be forwarded to International Construction Warranties for approval along with other requested reports that form part of the conditions placed on the warranty.

9.8 External Treatments Existing cladding can be retained if it can be shown that:

•

Adequate provision for movement has been allowed.

•

The system is maintaining the integrity of the building.

•

It is adequately fixed and the expected life span of the fixings where appropriate is in excess of 15 years.

If the above situations cannot be satisfied, then a new external cladding or rendering system will need to be installed.

•

The cladding material is free from and defects.

9.9 Internal Treatments An alternative to preventing moisture penetration by using externally applied claddings and renders is internally applied methods. Systems are available that are installed on the inside of existing walls to prevent moisture penetration reaching the internal accommodation. These include: •

•

Impervious sheet and drained sheet systems. Systems to prevent water penetration should be installed in accordance with the manufacturer’s recommendations and should have third party accreditation acceptable to International Construction Warranties Limited. i.e. BBA Certification.

Independent metal or timber framed systems. These should not be fixed to the existing masonry walls but fixed at the ‘head and base’ to avoid direct contact. Ventilation should be provided to avoid build-up of condensation between the masonry and the inner lining system.

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9.10 Interstitial Condensation Vapour control layers may need to be incorporated on the warm side of the thermal insulation. Voids and cavities may also need to be ventilated.

9.11 Surface Condensation Under certain conditions the warmth from sunlight falling onto damp solid masonry wall can drive moisture inwards and form condensation on the outside of a vapour barrier. Diagrams 4.44 and 4.45 in the following pages indicate two methods of upgrading the thermal properties of existing solid walls whilst attempting to limit the risk of summer condensation.

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9.12 Control of Moisture Penetration Measures should be taken to ensure that thermal insulation in cavities does not encourage the passage of damp from the ground or from the exterior of the building to the inside of the building.

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9.13 Thermal Insulation of Walls and Claddings Various methods exist to upgrade the thermal insulation of existing walls and floors. Regardless of the methods adopted, it is essential that risks associated with increased thermal insulation are minimised, including:

•

Surface condensation caused by improvements to draught proofing of the building.

•

Interstitial condensation caused by moisture laden air passing from a dwelling to within the fabric of the structure and condensing on cooler surfaces.

•

Increased risk of damp penetration caused by filling of cavities with insulation.

•

Maintaining the robustness of the external and internal wall surfaces by the provision of adequate mechanical protection over insulation materials, e.g. externally applied insulation systems with render coat mechanical protection.

•

Avoidance of cold bridges around openings and when structural elements extend through thickness of the building envelope.

•

Where planning restrictions prevent the thermal upgrade of the building then International Construction Warranties Limited may deem it appropriate to add an endorsement to the policy regarding the risk of condensation.

It should be noted that these diagrams are for upgrading thermal values but are not always to prevent moisture penetration.

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9.14 Render Application Rendering for Conversion/Refurbishment

Protection of Render

Where the condition and bond of the existing render can be shown to be adequate it can remain subject to the following exclusions:

Renders are vulnerable to damage through exposure to extremes of temperature during the first few days. Therefore, the following appropriate precautions should be arranged in advance:

•

If the render bridges the dpc.

•

Above door and window openings where it is necessary to examine the type and condition of the lintels.

•

Where there are signs of structural movement in the building and further investigation is required.

Guidance on this subject is available: BRE Good Building Guide 23 & 24 •

Assessing external rendering for replacement or repair.

•

Repairing external rendering.

•

In hot weather, the wall should be shaded from the direct heat of the sun or the work programmed to be carried out in the shade.

•

In cold weather, rendering should not be attempted when there is a risk of frost occurring during the day or the following night.

•

Air temperature should be at least 50C at the time of application.

•

When rendering has been applied, it should be prevented from drying out for two or three days until the mortar has hardened.

•

In drying winds, it may need to be kept damp by gentle spraying.

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9.15 Finishes Plaster for Conversions/Refurbishment Where the condition and bond of the existing plaster can be shown to be adequate, it can remain with exception of the following:

The existing plaster should be removed where: •

Where rising damp is present.

•

Where a chemical damp-proof course is installed.

•

At the junction of external walls and part walls to see if they are properly bonded.

•

Above openings to examine the makeup and condition of lintels.

•

Where there is possibility of bond timbers which may have decayed.

Where a chemically injected damp-proof course is installed it is necessary to remove the plaster one meter above the dpc level or 600mm above any apparent salt line/ dampness whichever is the higher. Re-plastering work should be delayed as long as possible in order to encourage rapid evaporation of residual moisture and the building should be well ventilated during the drying period.

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Plastering work must comply with insurance backed guarantee on damp proofing measures and is acceptable to International Construction Warranties Limited and the chemical damp-proof course manufacturers’ recommendations. Recommended plasters usually incorporate adhesives to increase resistance to the passage of hygroscopic salts from the wall into the plaster. Gypsum plaster should not be used in conjunction with chemically injected damp proof courses. The plaster should not bridge the damp-proof course or be in contact with the ground floor slab.

9.16 Further Guidance The use of large panels of glass in cladding of walls and roofs where the cladding is not divided into small areas by load bearing framing requires special consideration. Further guidance is provided in the following documents: UK Guidance –BBA website www.bbacerts.co.uk The Institution of Structural Engineers’ Report on ‘Structural use of glass in buildings’ dated 1999, available from 11 Upper Belgrave Street, London SW1X 8BH. ‘Nickel sulfide in toughened glass’ published by the Centre for Window Cladding and Technology dated 2000.

Further guidance on cladding is given in the following documents The Institution of Structural Engineers’ Report on ‘Aspects of Cladding’ dated 1995. The Institution of Structural Engineers’ Report on ‘Guide to the structural use of adhesives’ dated 1999. BS 8297 Code of practice for the design and installation of non-load bearing precast concrete cladding. BS 8298 Code of practice for the design and installation of natural stone cladding and lining.

Additional guidance on fixings is given in the following documents - ETAG No. 001 1997 Guideline for European Technical Approvals of Metal Anchors for use in Concrete, European Organisation for Technical Approvals, (EOTA) Brussels. All EOTA parts may be downloaded in English from www.eota.be. English version published by the British Board of Agreement. - Part 1 Anchors in General - Part 2 Torque Controlled Anchors - Part 3 Undercut Anchors - Part 4 Deformation Controlled Anchors - Part 5 Bonded Anchors - Part 6 Metal anchors for redundant use in concrete for lightweight systems.

- BS 5080 Structural fixings in concrete and masonry Part 1 1993 - CIRIA Report RP 566 Cladding Fixings: Good practice guidance - CIRIA Reports C579 and C589 Retention of masonry facades - Best practice guide. Guidance Notes published by the Construction Fixings Association - Guidance Note: Procedure for Site Testing Construction Fixings (1994) - Guidance Note: European Technical Approvals for Construction Fixings (1998) - Guidance Note: Anchor Selection (1995) - Guidance Note: Fixings and Fire (1998) - Guidance Note: Anchor Installation (1996) - Guidance Note: Bonded Anchors (1999) - Guidance Note: Heavy Duty Expansion Anchors (1997) - Guidance Note: Fixings for Brickwork and Blockwork (1997) - Guidance Note: Undercut Anchors (1998) - Guidance Note: Fixings and Corrosion (2002)

Following the latest consultation of cladding and fire risk assessment, we would expect all cladding materials to also meet the following new British Standards once the policies and standards have been fully confirmed. BS 8414-1. Fire performance of external cladding systems. Part 1. Test method for non-loadbearing external cladding systems applied to the masonry face of a building. BS 8414-2. Fire performance of external cladding systems. Part 2. Test method for non-loadbearing external cladding systems fixed to and supported by a structural steel frame. BS 9414. Fire performance of external cladding systems. The application of results from BS 8414-1 and BS 8414-2 tests.

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Roof

10.0 Roofs Statutory Requirements

Design

Building Regulation Requirements

Where a specialist design is requested or required, they shall:

Any roofing structure should be suitably designed by a competent person and the calculations provided to evidence that they meet the requirement of Approved Document A of the Building Regulations. All roofing systems are exposed to loadings and forces and they must be constructed in a manner that distributes these to the ground. It is important to follow the guidance set in Approved Document A.

•

Be designed by a suitably qualified person.

•

Be supplied with clear precise instructions.

•

Be supported with structural calculation when outside the guidance of the Approved Documents.

•

Be available for inspection by ICW.

Workmanship During the construction phase: •

All workmanship must be completed in a competent workmanship like manner.

•

Protected against unnecessary damage.

•

Design and Installation specifications are followed.

•

Products and materials are inspected for suitability for their purpose.

Materials All materials used shall: •

Be adequately protected and stored in a correct manner.

•

Comply with relevant British Standards or equivalent European Technical Specification with the certification available for inspection by ICW.

•

Be installed as per Manufacturers details.

•

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10.1 Bracing and Restraint “The building roof shall be constructed so that the combined dead, imposed and wind loads are sustained and transmitted by it to the ground safely; and without causing such deflection or deformation of any part of the building, or such movement of the ground, as will impair the stability of any part of another building.”

Wind Loading For the roof to withstand forces applied through wind loading the construction of the roof should be calculated by a competent person and installed following the manufacturer’s installation guide. The roof should be suitably restrained as shown in Approved Document A of the Building Regulations. Generally, roofs are secured by fixing of a timber wall plate on a bed of mortar. This wall plate requires fixing to the internal wall by way of holding down straps spaced at a maximum of 2 m and mechanically fixed with screws. Securing of roofs to the supporting structure roof timbers are normally supported on a timber wall plate or similar, which should be levelled using a spirit level so that loadings from the roof are directed perpendicularly down the supporting wall. There is also a requirement to ensure that holding down straps are provided in areas of severe wind exposure where required by the roof design and these should be installed subject to structural engineers’ details.

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Holding Down Straps

10.1

Bracing and Fixing To ensure the roof is adequately braced, it is recommended that the roof is secured to the gable wall this can be done by using a 100mm x 25mm timber, twice nailed to roof timbers using 65mm long, 3.35mm diameter galvanized wire nails. The installation of the roof should also have incorporated diagonal and longitudinal bracing, this will form part of the structural design of the roof truss and be installed as per engineersâ&#x20AC;&#x2122; details.

Lateral Restraint Straps Roofs should provide lateral restraint to all walls running parallel to them, by means of 30mm x 5mm galvanized or stainless-steel restraint straps at 2m centres. Further guidance can be found in Approved Document A.

Loft Hatch Provision In most cases here will be a service loft hatch placed within the roof structure, it is the responsibility of the roof designer to ensure the bracing to the loft opening adequately meets the additional loads placed upon it. Also, the hatch itself must be thermal efficient and have adequate fire protection to achieve the requirements of Approved Document L and B. It is common practice that water storage tanks are located within the roof space. It is the responsibility of the roof designer to ensure the roof truss can accommodate the extra loading and the material used to support the tank i.e. chipboard or floor boarding is suitable for its intended purpose. Alternatively, the installation of joist hangers built into the walls with joists spanning to facilitate a storage tank may be used this is however subject to structural engineerâ&#x20AC;&#x2122;s design.

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10.2 Fire Stopping Fire Stopping and Compartmentation

Junctions of Compartment Walls with Roof

The use of compartmentation enables the roof space to be sub-divided to restrict the spread of fire. It is advisable that the roof compartment should have the following design elements to ensure the spread of fire complies with that of approved Document B. This will be achieved by the installation of cavity barriers at:

There is always the possibility that a fire could penetrate into the roof void and spread externally to the adjacent compartment, to reduce this risk it is advisable that either side of the roof there is a zone of 1500mm wide on either side that has a covering designated AA, AB or AC on a substrate or deck of a material of limited combustibility.

•

Within boxed eaves at separating wall position.

•

Junctions of separating wall and external cavity wall.

•

Junctions of compartment wall and compartment floor.

•

Junctions of separating wall with roof, under roof tiles.

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10.3 Roof Coverings Tiles & Slates

Note on Fixing

Guidance and Legislation

The use of mortar to bed roofing tiles is no longer accepted and each tile must be mechanically fixed to prevent uplift from wind loading.

The guidance that covers tiled and pitched roof coverings is BS 5534: ‘Code of Practice for slating and tiling (including shingles)’ which provides recommendations on how to design, install and apply coverings as well as providing information on their performance. The British Standard should be read in conjunction with BS 8000-6. ‘Workmanship on building sites: code of practice for slating and tiling of roofs and claddings’ as this makes reference to the correct installation and laying of clay and concrete tiles. And where needed regulation 7 of the manual to the Building regulations may be used. As roof spaces create condensation on their surfaces it is advisable to use guidance found in (CAWS) Common Arrangement of Work Section classifications, H60, H61 and H65. BS 5250: ‘Control of Condensation in Buildings’. The classifications give detailed descriptions of the causes and effects that interstitial and surface condensation have in roofs.

Performance of Tiles and Slates The way rain penetrates the roof covering is dependent on the location of the building, the rainfall rate for that location, average wind speeds and other factors such as the ability of the product (tile or slate) to rest the ingress of rain and snow. There are several ways that this may occur: These include: •

Wind-driven snow.

•

Unprecedented rain and snowfall.

•

Capillary action and rainwater creep.

•

Raindrop bounce and negative pressure rain suction.

•

Driving rain, deluge rain and flooding. 126

10.3

Fixing Specification

Ventilation

All fixings must meet the requirements found in BS5534 and BS EN 1991-14:2005+A1 ‘Euro -Code 1 and Should also be designed in conjunction with the zonal fixing method as shown in table below.

Ventilation is required to reduce the risk of interstitial condensation forming on the underside of the impermeable felt membrane and settling on the timber rafters. When designing ventilation for roofs the guidance found in Approved Document F should be followed as a minimum as well as additional guidance found in clause 8.4 of BS 5250 and BS EN ISO 13788.

Zonal Fixing Specification Zonal Fixing

Single Lap Tiles

No fixings required

Each tile once nailed (right hand nail hole – flat tiles)

Each tile twice nailed (flat tiles only)

Double Lap Tiles

Cold Roofing Systems Refer to manufacturer

Each tile clipped

Each tile once nailed and clipped

Each tile twice nailed and clipped

Note: 1.

The manufacturer may also specify the use of improved nails for fixing tiles, e.g., ring shank nails. Where these are required, the Zonal fixing specification letter will be marked with an asterisk, e.g., C*.

Manufacturers may define additional fixing specifications to those in the table and assign fixing specification letters from ‘G’ onwards.

In some cases, the manufacturer may specify a ‘proprietary fixing system’ and this will be marked ‘PS’. The manufacturer should be contacted for details of the requirements for this fixing method. 127

If condensation is not dealt with correctly than this can become harmful to the occupants and it is advisable to consider BS 5250 ‘Code of Practice for Control of Condensation in Buildings’ Section 8.4 ‘Roofs’ as well.

Cold roof construction is where the insulation is laid between the ceiling joists. This then means that everything above the insulation, such as the rafters, is colder than the living space. Warm, moisture laden air can permeate up through the ceiling. When it reaches the cold roof space such as the loft compartment the change in temperature creates condensation on the timbers, underlay etc. By ventilating the roof void the free flow of air will eliminate the build-up of condensation forming.

10.3

Warm Roofing Systems

Underlay

A warm roofing system is where the insulation is laid on top of the rafters, or in between the rafters everything below the insulation is as warm.

Underlay used within the building should comply with the requirements of BS EN 13859-1 and be suitably BBA certificated. Fully supported underlays, should be:

Thermal Insulation

•

The level of insulation and type will depend on the buildings SAP calculation and may be in several forms or a mixture of several types for example:

2HR* underlay to BS EN 13859-1 Class W1 water penetration classification with third party certification for the use intended.

•

3LR† underlay to BS EN 13859-1 Class W1 water penetration classification with third party certification for the use intended.

•

Mineral Wool

•

Rigid polyisocyanurate (PIA Board)

•

Multi Foils

All the insulation used within the building should achieve an A+ rating when compared to the BRE Green Guide and certified under BBA certificate numbers 95/3197 and 09/4667. Thermal insulation must be installed to meet current Building Regulations to an acceptable level of workmanship avoiding cold bridges. At all times the insulation should be installed to meet the manufacturers installation guide and there should be no areas exposed that would allow thermal bridging to take place.

Nails for the Underlay Fixing Clout nails to BS EN 10230-1, should be used when fixing the underlay, these nails should be no less than 3.0mm diameter and 20mm in length and be constructed of a suitable metal such as copper, alloy or aluminium.

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10.3

Unsupported Underlays

Vapour Control Layer (VCL)

•

BS 8747 Class 1F reinforced bitumen or Class 5U polyester reinforced bitumen.

•

HR* underlay to BS EN 13859-1 Class W1 water penetration classification with third party certification for the use intended.

If a VCL is installed it should be placed on the warm side of the insulation and be correctly installed to manufactures details and guidance found within BS5250: Code of practice for control of condensation in buildings.

•

LR† underlay to BS EN 13859-1 Class W1 water penetration classification with third party certification for the use intended.

Vapour Control Layer and Breathable Membrane Vapour control layers are positioned to the inside of the insulation in order to minimise the amount of warm moist air entering the construction. Breather membranes are positioned to the outside of the insulation acting as a weather barrier while still allowing moisture particles to escape from the inside.

Upto 450mm Span

Upto 600mm Span

Width mm

Depth mm

Width mm

Depth mm

Natural: Sized or Random

Fibre-Cement or Concrete

Width mm

Depth mm

Width mm

Depth mm

Double Lap

Single Lap

Clay and Concrete Tiles

129

Membranes should always be installed to manufacturer’s details and installed following the requirements of BS 5534.

All timber battens should meet the requirements of BS5534 and be fixed using the guidance and fixing details found in BS 5534.

Minimum size of batten

Slates Double Lap

In addition to improving energy efficiency, breather membrane solutions offer longlasting protection against several threats to building integrity, including condensation and infiltration by water and air. Breathable membranes offer a secondary water shedding layer that prevents moisture entering the building but allows moisture to pass out.

Timber Battens

Recommended Batten Size from BS:5534

Application

Breathable Membranes

Timber Frame

11.0 Timber Frame Statutory Requirements

Design

Structural Design

Where a specialist design is requested or required, they shall:

With every timber framed structure, the structure should be able to withstand wind, snow and dead loads and transmit these safely into the ground. All timber frame structures shall be designed in accordance with Euro-Code 5. The whole timber frame structure should be calculated by a suitably qualified person.

•

Be designed by a suitably qualified person.

•

Be supplied with clear precise instructions.

•

Be supported with structural calculation when outside the guidance of the Approved Documents.

•

Be available for inspection by ICW.

Workmanship During the construction phase: •

All workmanship must be completed in a competent workmanship like manner.

•

Protected against unnecessary damage.

•

Design and Installation specifications are followed.

•

Products and materials are inspected for suitability for their purpose.

Materials All materials used shall: •

Be adequately protected and stored in a correct manner.

•

Comply with relevant British Standards or equivalent European Technical Specification with the certification available for inspection by ICW.

•

Be installed as per Manufacturers details.

•

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11.1 Introduction To offer a definition of a timber frame building they are generally constructed of external walls and floors and consist of load-bearing solid timber studs at pre-calculated centres which are insulated and lined with a structural sheathing board, breather membrane, cladding, vapor control and fire resistant linings.

Grading of Structural Timber All structural timber shall be graded in accordance with BS EN 14081: Timber structures - Strength graded structural timber with rectangular cross section. All load-bearing solid timber studs, rails, binders and sole plates should be of a minimum dry graded C16, although the use of C24 is readily available.

SIPS (Structural Insulated Panels) Structurally Insulated Panels (SIPs) are a composite panel and must only be installed by an accredited installer.

Treatment of Structural Timber All load-bearing timber components shall either be treated in accordance with BS 8417.

Quality assurance Timber Frame manufacturers and installers should possess the correct and current certification from one of the following quality assurance schemes: •

BM TRADA Q Mark for timber frame;

•

ISO 9001;

•

CE Marking.

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11.2 Substructure The substructure should be checked for dimensional accuracy against that of the timber frame supplier.

11.3 Sole Plates Sole plates should be located at least 150mm above finished external ground level as per guidance found in Approved Document C. The sole plates should be fixed to the foundations with shot fired nails. Any additional method would need to be from an accredited scheme or with structural engineers fixing details.

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11.4 Sheathing Boards Suitable sheathing boards are required to brace the timber frame structure and the following boards are acceptable:

Sheathing boards must comply with BS EN 13986: Wood-based panels for use in construction - Characteristics, evaluation of conformity and marking.

•

Orientated Strand Board (OSB).

•

Plywood.

OSB should be grade 3 or 4 in accordance with BS EN 300: Oriented Strand Boards (OSB) - Definitions, classification and specifications.

•

Impregnated soft board.

•

Medium board.

•

Tempered hardboard.

Plywood should be Class 3 Structural in accordance with BS EN 636: Plywood. Specifications.

•

Other board material with suitable third-party certification for primary racking resistance.

Impregnated soft boards should be Type SB.HLS in accordance with BS EN 622-4: Fibreboards. Specifications. Requirements for soft boards.

Tempered hardboards should be Type HB. HLA1 or HB.HLA2 in accordance with BS EN 622-2: Fibreboards. Specifications. Requirements for hard boards.

Medium board should be type MBH.HLS1 or MBH.HLS2 in accordance with BS EN 622-3 Fibreboards. Specifications. Requirements for medium boards.

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11.5 Fixing All sole plate fixings and holding down products should be austenitic stainless steel, be structurally calculated and fit for its intended purpose.

The sole plate is to be anchored down to prevent lateral and vertical force ties should be placed so that they are in line down to prevent lateral and vertical force with the vertical studs.

Wall ties should be placed so that they are in line with the vertical studs.

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11.6 Breather Membrane The timber frame should be fitted with a breather membrane with the following characteristics: •

A Type 1 membrane in accordance with BS EN 13859-2 (withdrawn BS 4016 may also be used for reference).

•

Self-extinguishing.

•

Securely fixed to protect the outside face of the timber frame structure with austenitic stainless-steel staples.

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11.7 Fire Stopping Cavity Barriers The purpose of the cavity barrier is to prevent smoke and flame spreading within concealed spaces. Acceptable materials that may be used are as follows: •

Timber at least 38mm thick.

•

Mineral wool slab.

•

Calcium silicate, cement-based or gypsum-based board at least 12mm thick.

•

An independently assessed and certified proprietary product.

It is recommended that the guidance of the manufacturers detail is followed when installing the above products.

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11.8 Internal Vapor Control Layer

British Standards

The purpose of the Vapor Control Layer or VCL is to mitigate the risk of interstitial condensation and to prevent the passage of moisture through the structure of the wall. There are various VCL available and it is recommended that the installer follows the technical guidance produced by the manufacturer.

•

BS 5268-3:2006 Structural use of timber. Code of practice for trussed rafter roofs.

•

BS 5268-6.1:1996 Structural use of timber. Code of Practice for timber frame walls. Dwellings not exceeding seven storeys.

•

BS 5268-6.2:2001 Structural use of timber. Code of Practice for timber frame walls. Buildings other than dwellings not exceeding four storeys.

•

BS EN 14081-1:2005 Timber structures. Strength graded structural timber with rectangular cross section. General requirements.

•

BS EN 13986:2006 Wood-based panels for use in construction. Characteristics, evaluation of conformity and marking.

•

BS EN 300:2006 Oriented strand boards (OSB). Definitions, classification and specifications.

•

BS EN 622-2:2004

Generally, various versions/types of plasterboard provide this function.

•

BS 4016:1997 Specification for flexible building membranes (breather type).

Insulation Materials

•

The use of insulation materials will be dependent on the buildings SAP calculation and it is advised that the manufacturer’s details are followed when installing.

BS EN 845-1:2003+Amendment 1:2008 Specification for ancillary components for masonry. Ties, tension straps, hangers and brackets.

•

BS 5268-2:2002 Structural use of timber. Code of practice for permissible stress design, materials and workmanship.

•

BS 5268-4 Section 4.1:1978 Structural use of timber. Part 4 Fire resistance of timber structures. Section 4.1 Recommendations for calculating fire resistance of timber members.

•

BS 8417:2003 Preservation of timber. Recommendations.

•

BS EN 1995-1-1:2004+A1:2008 Euro-Code 5 Design of timber structures. General. Common rules and rules for buildings.

•

BS EN 636:2003 Plywood. Specifications.

•

BS5534 Code of Practice for Slating & Tiling.

Wall Linings The internal wall of the timber frame has several functions which: •

Provide the final finish to be applied, paint, wallpaper, tiles etc.

•

Provides structural stability of the wall.

•

Provides the correct period of fire resistance of the wall.

•

Provides acoustic performance of the wall.

•

Provides separation.

External Claddings The timber framed structure should be fitted with an appropriate cladding system which may take the form of brickwork, rendered blockwork or lightweight rain screen system. Whichever system is used adequate provision for drainage and ventilation should be provided.

Air Tightness At all times the technical details, manufacturer’s installation techniques and information designed within the SAP calculation should be adhered too to ensure air tightness of the building in accordance with relevant guidelines.

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Modern Methods of Construction

12.0 Modern Methods of Construction (MMC) For all MMC properties, we will need to carry out a technical assessment of your MMC project before we can agree to register it for cover under our warranty policy scheme.

By providing us with all the relevant information when you notify us of the project, we will be able to complete our desktop overview and arrange a visit without delay.

The assessment process will include a desktop study and four factory quarterly inspections to ensure conformity with our technical standards. We understand the need to make quick progress on this assessment. Below, we have set out how we can help each other to streamline the assessment process.

What We Expect •

All external walls must prevent moisture penetration to the inside and be insulated to building regulation requirements. This can be achieved with a suitable system, which will both insulate the fabric and externally applied render/insulation system.

•

Any habitable areas either below or partially below ground level must be provided with a minimum grade 3 tanking system or equivalent.

•

All repairs and treatments identified in the expert’s and engineer’s reports.

•

In addition to the contractors guarantee, a min 10-year insurance backed guarantee is required for chemical dpc’s, specialist and flat roofing systems and proprietary externally applied weather proofing/insulation systems.

•

Windows, doors and internal services should be to modern standards.

•

Life of building to be at least 60 years in accordance with CML requirements.

The flow chart overleaf shows you the stages, from notification of the project to our decision to accept, or unfortunately on some occasions decline.

What are we looking for? In order to understand your project, we need to know as much as possible about it as soon as possible. In particular we need to see your: •

Project specification – Plans and specifications.

•

Structural adequacy of elements and confirm life expectancy of building.

•

Experts reports – these will be in addition to the structural engineer’s report and should include specialist reports on damp proofing/tanking systems, test data from manufacturers.

•

Independent assessment of components or system from BBA, BRE, WIMLAS or conformity to International, European and British Standards.

•

Guidance from industry bodies, TRADA, CIBSE, CIRIA etc.

•

Discussions with manufactures, builder and client.

•

Past performance of similar systems and maintenance requirements.

•

Test evidence.

•

Third party Manufacturer’s Warranties. 138

12.0

Flow chart â&#x20AC;&#x201C; Modern Methods of Construction Process

Application loaded onto database, details forwarded to Technical ICW Application

Department. Any additional plans, reports

Requested additional

Desktop appraisal

information received.

undertaken.

etc required sent to applicant.

Technical Department arranges factory inspection.

139

Technical Department

MMC building accepted

able to fully accept

as part of our warranty

proposal or decline

scheme if approved by

proposal.

Technical Department.

Quotation sent to Developer/Builder as per application if approved by Technical Department.

Internal Services

13.0 Internal Services Statutory Requirements

Design

Building Regulation Requirements

Where a specialist design is requested or required, they shall:

The requirements of the Approved Documents of the Building Regulations should always be followed, and all the relevant approvals sought from the Building Control Body.

•

Be designed by a suitably qualified person.

•

Be supplied with clear precise instructions.

•

Be supported with structural calculation when outside the guidance of the Approved Documents.

•

Be available for inspection by ICW.

If any calculations are required to support the proposed design, then these should be provided by a suitably competent and qualified person. The calculations will need to be designed so as they safely distribute loads and forces to the foundations.

Workmanship

Water Services and Supply

During the construction phase:

Service supplies and installations should be designed by an expert, considering the required pressures and flow rates from the incoming mains, detailed drawings should be available for inspection.

•

All workmanship must be completed in a competent workmanship like manner.

•

Protected against unnecessary damage.

•

Design and Installation specifications are followed.

•

Products and materials are inspected for suitability for their purpose.

Materials

Protection from Freezing Where water services are located within unheated spaces it is important to reduce the risk of freezing, insulation should be installed it is accepted that minimum insulation thickness of 24mm will be adequate for the prevention of freezing to domestic installations.

All materials used shall: •

Be adequately protected and stored in a correct manner.

•

Comply with relevant British Standards or equivalent European Technical Specification with the certification available for inspection by ICW.

•

Be installed as per Manufacturers details.

•

13.0

Hot Water Services Hot water supply may be provided from an instantaneous source such as a combi boiler or the provision of a storage system, where a cylinder is installed it must have the access to all relevant parts as specified in the installation manual for maintenance, any pipe work installed in uninsulated spaces must be insulated to prevent freezing. Hot water services are to be designed with the following min flow rates:

Location

Min Flow Rate (l/s)

Temperature

Bath Tap

0.3

Wash Hand Basin

0.15

Shower

0.1

Sink

0.2

141

13.0

Unvented Hot Water Systems

Examples of acceptable discharge arrangements are:

Where an unvented system is installed it must be accompanied with a third-party accreditation and the installation completed by a competent person.

•

To a trapped gully with the end of the pipe below fixed grating and above water seal.

To minimize the danger from excessive pressure, the systems should include a min of two independent safety devices, this is in addition to any thermostat provided to control the desired temperature of the stored water, the design of the safety devices should also take into consideration the location and configuration of the devices.

•

Downward discharge at low level, up to 100mm above external surfaces such as car parks, hard standings etc, are accepted providing that a wire cage or similar guard is positioned to prevent contact whilst maintaining visibility.

•

Discharge at high level into a metal hopper and metal downpipe with the end of the discharge pipe clearly visible or onto a roof capable of withstanding high temperatures and 3m from any plastic guttering system that would collect such discharges.

Unvented systems should be indelibly marked with the: •

Manufacturers details.

•

Model reference.

•

Rated storage capacity.

•

Operating pressure of the system and expansion valve.

•

Relevant operating data on each safety devices fitted.

•

The max primary circuit pressure and flow temp of indirect hot water storage system units or packages.

In addition, a warning sign should be indelibly marked on the hot water storage system unit or package so that it is visible after installation.

142

13.0

Electrical Electrical installations should be in-line and comply with the IEE Wiring Regulations and BS7671, Installations should be registered with a recognised body such as NICEIC and a certificate should be issued on completion. There is a requirement to supply outlets to rooms as identified below:

Room

Outlets

Living Room

Dining Room

Kitchen

Utility

Double Bedroom

Single Bedroom

Hall/Landing

Loft

143

For structural stability avoid back to back chasing, and chasings should be fully filled with mortar prior to covering.

Cables that are not protected by a conduit should be located horizontally or vertically from the outlets within the green area of the diagram and a minimum of 50mm from the surface of the wall.

13.1 Space Heating Space heating systems should comply with the appropriate following British standards and codes of practice:

Whole home heating systems should be designed to provide internal temperatures as shown below with an assumed external air temperature of -3 degrees:

Code

Code of Practice

Location

Temperature in Degrees

Air changes

BS5410

Code of practice for oil firing

Living Room

1.5 per hour

BS5449

Specification for forced circulation hot water central heating systems for domestic premises

Dining Room

1.5 per hour

Kitchen

2 per hour

BS5482-1

Code of practice for domestic butane- and propane-gas-burning installations Bedrooms

1 per hour

BS5864

Installation and maintenance of gas-fired ducted air heaters Bathroom

2 per hour

BS5871-1

Specification for the installation and maintenance of gas fires, convector heaters, fire/back boilers and decorative fuel effect gas appliances

Separate WC

2 per hour

Design, installation, testing and maintenance of services supplying water for domestic use within buildings and their curtilages

Hall and Landing

2 per hour

BS6700

BS8303

Installation of domestic heating and cooking appliances burning solid mineral fuels

144

13.1

Windows and Doors All external timber should be a species classified as suitable in BS EN 942 and meet the requirement found in TRADA Wood Information Sheets 3.10 and 4.16. Products which are not constructed of timber i.e. Aluminium, Glass and UPVC should meet the requirements of the following: •

BS 4873 Aluminium windows.

•

BS 5286 Specification for aluminium framed sliding.

•

BS 6510 Steel windows and doors; • BS 7412 PVC-U windows; • BS EN 514 PVC-U windows.

All doors should meet the requirements of the buildings SAP calculation and should also ensure that adequate means of escape and ventilation are available.

145

13.2 Escape Windows Means of Escape Approved Document B requires that escape is required from every habitable room and this will be achieved by installing windows with a clear openable area of 0.33m2. This can be achieved by ensuring at least one dimension has a minimum of 450mm wide. The access to this window cannot be higher than 1100mm from the floor level.

Protection from Falling Guidance found in Approved Document K2 specifies a minimum guard height of 800mm to window openings in the external wall. It is advisable that where possible windows are installed higher to prevent guarding. However, in the situation where guarding is required, and the openable area of the window is less than 800mm the window will require permanent guarding to BS 6180.

Installation and Workmanship As soon as possible windows and doors should be installed to ensure the water tightness of the building. All the windows and doors should be to the correct sizes, dimensions, specifications and should be installed as per manufacturerâ&#x20AC;&#x2122;s details. There should be no gap greater than 10mm around the opening, and for gaps less than 5mm the sealant should cover the frame and the masonry by 6mm to ensure weather tightness.

146

13.3 Safety Glazing Safety Glazing for Critical Locations In all cases the minimum requirement of Approved Document K (4) of the Building Regulations 2013 Protection against impact with glazing must be followed. K4.—Glazing, with which people are likely to come into contact whilst moving in or about the building shall: •

If broken on impact, break in a way which is unlikely to cause injury; or

•

Resist impact without breaking; or

•

Be shielded or protected from impact.

147

Conversion

14.0 Inspection Process International Construction Warranties Limited will carry out targeted inspections on all converted and refurbished properties. The main purpose of carrying out inspections is to reduce the risk of latent defects through a tightly targeted programme of risk management. Each development being assessed on its merits including; the complexity of the site, site environment, method of construction and the experience of the developer / builder. When registering your site with us, you will receive contact details of your allocated International Construction Warranties Limited surveyor or appointed approved inspector, with who you can arrange your first site visit. In order for us to gather a full understanding of your development and what you wish to achieve, your appointed surveyor will arrange a pre-planning meeting with your site manager with the purpose of discussing the development as a whole, including programme of works and the method of construction. Following this meeting your appointed surveyor will discuss your risk management programme, targeting site inspections to suit the agreed stages of the development.

Our Inspection programme of risk management cannot eliminate all risks but together with the following stage inspection memoirs will endeavour to: -

The programme of risk management inspections is planned to cover all significant structural and weather penetration elements. At each inspection, your appointed surveyor records all the data gathered and provides a site generated report for each plot where technical advice is given, or a defect is recorded. The following inspection overview will indicate the elements of construction that should be completed and will allow the site manager to check works during the build to completion and provide an indication into the aspects of construction your appointed surveyor will want to inspect. The recorded information is held by International Construction Warranties Limited providing an on-going record of information for each plot. This provides an invaluable source of management data and, as a unique service to our clients; we can offer a regular reporting service. Please note: Works that are not acceptable to International Construction Warranties Limited will require rectification before an Insurance certificate can be produced.

Conversion Construction Stage’s Site Overview

Commencement of site/Site Overview

Minimise the risk of defects going undetected.

Initial Inspection

Foundations (If applicable) & Strip out of existing structure

•

Increase satisfaction of the new building user whether this be residential.

Intermediate Inspection

Superstructure to Roof including pre-plaster

•

Reduce the likelihood of claims e.g. For the Builder/ Developer during the two-year defect liability period and for the End Insurer of the Policy.

Completion Inspection

Final Inspection prior to Handover

•

Reduce any uncertainties.

•

The number of inspections carried out on the construction of your development will vary depending on initial and on-going risk management assessments carried out by your appointed surveyor. These occur at three different stages throughout the course of the build in order to identify areas where assistance can be given to reduce the number of latent defects at each stage of construction. Your appointed surveyor will carry out at least three inspections throughout the build, however, the amount and frequency of inspections will vary depending on the complexity and speed of construction. 148

14.1 Site and Construction Overview Stage (Site Overview) Checklist

Item of construction to be quality checked

Builder Check

ICW Inspect

General â&#x20AC;&#x201C; The ICW surveyor will check all details on-site are identical to those quoted and uploaded onto the Smartsurv Inspection Application i.e. Plot numbers, site address, contact details etc.

ICW surveyor to introduce themselves and to take note of site agents name and contact details.

Check that all proposed plots under the current phase have been registered and that the plot numbers on- site are as those described on the SmartSurv application.

ICW surveyor to explain the on-site paperwork and inspection recording system.

Site wide elements - the ICW surveyor will discuss the type of construction to be adopted together with general observations on the ground conditions, foundation type and site wide elements.

The ICW surveyor will discuss the principles of the development on the following issues: Construction type Traditional or non-traditional or Modern Methods of Construction. Exposure conditions of the Site Have they been considered in the design. Are there any rooms to be constructed below ground? (habitable or non habitable and if so, are insurance backed guarantees going to be provided). Ground conditions: - type of subsoil - water table level - contaminants, gas etc - shrinkability if clay and trees (present or removed) - foundation design (standard / engineered) - difficult site condition i.e. sloping site - land drainage required Sound insulation: - are RSDâ&#x20AC;&#x2122;s to be used, unique numbers required - pre completion testing is this by UKAS or ANC member - from Approved Doc E pre completion testing required Is this by UKAS or ANC member

149

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

14.1

Item of construction to be quality checked

Builder Check

ICW Inspect

Foundations discussed in detail to establish the type and design (only applicable if new foundations are part of the new works): - strip - raft - piled - underpinning - other - existing ground obstructions - sulphates in the ground (cement considerations)

Tanking: - are there any walls to be tanked or require tanking - are there any basement areas and what is proposed to prevent water ingress, attention to detailing of junctions - structural design, wall, floor construction - ventilation, fire resistance and means of escape in case of fire - services passing through and land drainage around perimeter - is an Insurance backed Guarantee to be provided

Drainage: - mains drainage, foul and surface water - MH size and location, gradients and protection - non-mains drainage - septic tank / treatment plant / cesspool - size and location - vehicular access required - outfalls and porosity tests - soakaways - size, location and ground conditions (porosity tests) - land drainage Ground floor type: - ground bearing - beam and block or similar type - cast insitu concrete - timber

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

150

14.1

Item of construction to be quality checked

Builder Check

ICW Inspect

External wall type: - masonry cavity / solid - timber frame - steel frame - concrete frame / panel / other External wall insulation: - full fill - Partial fill - clear - other Movement joints: - location - type/design - restraint

Internal walls: - partition walls - type, loadbearing / non loadbearing - foundations - party walls - masonry - solid - cavity - dry lined or dense plaster - timber framed - metal framed - other

151

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

14.1

Item of construction to be quality checked

Builder Check

ICW Inspect

Upper floors: - floor type - timber, concrete, other - spans - fire resistance - insulation Party floor: - floor type - timber, concrete - sound performance - density or isolation

Roof - pitched, flat, mansard, other: - timber, steel, other - trusses or cut - fixing details Roof covering: - slates, tiles, thatch, high performance felts, lead, other - fixing specification - nailing / clipping, manufacturers details - roof penetrations - chimneys - stability and trays / flashings - parapets / copings - stability and trays / flashings - vents -flashings - roof lights - consider design, trimming and weathering

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

152

14.2 Foundation to Ground Floor Stage (Initial Inspection) Checklist

Item of construction to be quality checked

Builder Check

ICW Inspect

Foundations in place and constructed to comply with the Building Regulations and/or the relevant British Standards, checks made: - strip - raft - piled - underpinning - existing ground obstructions - sulphates in the ground (cement considerations)

Load bearing walls from foundation to dpc: - bricks and blocks below dpc - selection of bricks and resistance to ingress of moisture

Basements: - ensure that all tanking is correctly installed and linked to the dpc and dpm above of the above ground structure

Floors - all floor substructures in place and constructed to comply with the Building Regulations and or the relevant British Standards, checks made for: Timber: - size, centres, spans and grading of joists - fixings and bearings - multiple and trimming members - adequate ventilation - restraint straps and noggins - concrete - size and bearing of units - damaged units - no cavity obstructions and trimming of openings - adequate support to internal partitions and service entries filled - all dpcs linked to suitable dpmâ&#x20AC;&#x2122;s

153

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

14.2

Item of construction to be quality checked

Builder Check

ICW Inspect

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

154

14.3 Strip Out and Assessment of Original Structure Stage (Initial Inspection) Checklist

Item of construction to be quality checked

Builder Check

ICW Inspect

Walls - all walls to be plumb and structurally stable, checks made for: Masonry: - dpcs lapped and bedded on a smooth joint / proprietary damp proof measures - dpcs in place around all openings / proprietary damp proof measures - lintel bearings and beam supports correct Timber / steel frame system: - sole plate preparation and fixing adequate - plumb - decayed timber / replacement - cavity barriers correctly located - damage, notching and drilling of members - breather membrane intact Internal walls: - built off adequate support - masonry joints filled and bonding adequate Lintels and bearings

Floors - all floor substructures in place and structurally stable, checks made for: Timber: - size, centres, spans and grading of joists - decayed timber / replacement - adequate ventilation - restraint straps and noggins Concrete: - size and bearing of units - damaged units - no cavity obstructions and trimming of openings Adequate support to internal partitions

155

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

14.3

Item of construction to be quality checked

Builder Check

ICW Inspect

Roofs (internally) - all roofs to be weathertight and structurally stable, checks made for: - centres and sizes of joist, binders, purlins, struts and or trusses - decayed timber / replacement - fixings of timbers / members - trimming to openings - proximity of timbers to chimneys/ flues - damage and or notching / drilling - restraint straps and noggins in place - bracing - size, location and fixing - valley, hip and dormer roof details - penetrations and weathering - party and gable wall cut to profile and fire stopped (where applicable) - flue and vent connections - felt condition and laps - cross ventilation / warm roof detail Roofs (externally): - ensure that the batten sizes, spacing and fixings are compatible with the covering and each other - all finishes (tiles, slates, lead or felt) should be free from damage, laid to falls where appropriate and finished to a basic visual standard - all coverings should be nailed, fixed, clipped to the correct specification in accordance with the relevant British/European Standards or the manufacturers - original materials to be retained/altered or replaced

Miscellaneous: - Staircases - ensure that the staircase has a minimum suitable width, the correct headroom, pitch, riser and going, together with a correctly located and fixed handrail and balustrading - fireplaces, hearths and chimneys properly constructed - windows â&#x20AC;&#x201C; to be retained/altered or replace

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

156

14.4 Superstructure to Upper Floor Stage (Intermediate Inspection) Check List

Item of construction to be quality checked

Builder Check

ICW Inspect

General - items checked during this inspection will cover the quality of build and structural stability / future weather integrity of the structure from dpc to upper floor level.

157

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

14.4

Item of construction to be quality checked

Builder Check

ICW Inspect

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

158

14.4

Item of construction to be quality checked

Builder Check

ICW Inspect

159

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

14.4

Item of construction to be quality checked

Builder Check

ICW Inspect

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

160

14.5 Upper Floors to Pre-Plaster including Roof Structure Stage (Intermediate Inspection) Check List

Item of construction to be quality checked

Builder Check

ICW Inspect

General - always refer to the â&#x20AC;&#x2DC;Upper floors to Pre-Plaster including Roof Structure (Intermediate Inspection) check listâ&#x20AC;&#x2122; in addition to this list. Items checked during this inspection will cover the quality of build and structural stability / future weather tightness of the structure up to pre-plaster and including, roof construction. The structure may not yet be fully weather tight.

161

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

14.5

Item of construction to be quality checked

Builder Check

ICW Inspect

General - all structural items should be in place and completed, namely floors, walls, roof structure, staircases etc. In addition, all services, â&#x20AC;&#x2DC;first fixâ&#x20AC;&#x2122;, should be undertaken or almost complete.

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

162

14.5

Item of construction to be quality checked

Builder Check

ICW Inspect

Roofs (internally) - all roofs to be weathertight and structurally stable, checks made for: - centres and sizes of joist, binders, purlins, struts and or trusses - fixings of timbers / members - trimming to openings - proximity of timbers to chimneys/ flues - damage and or notching / drilling - restraint straps and noggins in place - bracing - size, location and fixing - valley, hip and dormer roof details - penetrations and weathering - party and gable wall cut to profile and fire stopped (where applicable) - flue and vent connections - felt condition and laps - insulation (if fitted at time) - continuity with external wall insulation - cross ventilation / warm roof detail

163

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

14.5

Item of construction to be quality checked

Builder Check

ICW Inspect

Services - generally all services and service paths should be fitted in accordance with the appropriate British Standard and/or governing bodies guidance.

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

164

14.5

Item of construction to be quality checked

Builder Check

ICW Inspect

Services - generally all services and service paths should be fitted in accordance with the appropriate British Standard and/or governing bodies guidance.

Miscellaneous: - staircases - ensure that the staircase has a minimum suitable width, the correct headroom, pitch, riser and going, together with a correctly located and fixed handrail and balustrading - first fix carpentry in place, plumb and square - fireplaces, hearths and chimneys properly constructed - windows - frames appropriately fixed and glazing installed correctly Conservatories - ensure that they are constructed to the same standard as the remainder of the home and form a weather tight and stable addition to the house. In addition, ensure that cavity trays are installed as per any other abutment. Integral garage - ensure that it is finished internally to a reasonable, basic level of decoration appropriate for its intended use. It is weathertight (not necessarily watertight, 100mm brick wall) and where abutting the house incorporates a suitable cavity tray and flashing. Ensure firestopping is complete. Basements - ensure that all tanking is correctly installed and linked into the cavity tray, dpc and dpm of the above ground structure.

165

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

14.5

Item of construction to be quality checked

Builder Check

ICW Inspect

External walls: - rendering - should be durable to resist the weather and impact - should not bridge the dpc Masonry - should be matched in colour and texture providing reasonable aesthetics - joints should be filled / pointed and consistent - mortar should be durable and consistent in colouring - corbelling and or plinths should not be excessive, thus enabling water to collect General - movement joints should be suitably located and filled - weepholes should be evident at all locations of cavity projections and at dpc level within timber frame construction - ensure that surfaces are reasonably plumb and level - lead flashings should be correctly located and fixed - dpc should not be bridged and located a min. 150mm above finished external ground level Level thresholds Should be suitably constructed to prevent damp ingress and allow adequate entry to the dwelling via a wheelchair

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

166

14.5

Item of construction to be quality checked

Builder Check

ICW Inspect

167

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

14.6 Completion Stage (Completion Inspection) Check List

Item of construction to be quality checked

Builder Check

ICW Inspect

Roof void, ensure that: - all flues terminate at the outside air via a proprietary terminal outlet - all tanks and pipes are adequately supported and insulated - all SVP and ventilation outlets are discharged adequately - restraint straps are correctly positioned and supported / blocked - bracing (where applicable) to the structure is adequately sized, fixed and positioned - insulation is adequate and correctly positioned (continuous) - All ducting in loft is adequately insulated - underfelt is continuous and not damaged - ‘warm roof’ - the roof void is completely sealed - ‘cold roof’ - adequate cross ventilation is maintained and unobstructed - check size, centres and damage to structural members forming the roof structure Miscellaneous Provide evidence of warranty backed insurance guarantees where applicable. The whole house should be clean, free from builder’s materials /rubble and be complete prior to handover / conveyance Staircases Ensure that the staircase has a minimum suitable width, the correct headroom, pitch, riser and going, together with a correctly located and fixed handrail and balustrading Flooring All flooring to be laid reasonably level and smooth to accept the intended finish. All boarding to be fixed securely to avoid squeaking, with floating floors to be adequately supported at door openings

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

168

14.6

Item of construction to be quality checked

Builder Check

ICW Inspect

Conservatories Ensure that they were constructed to the same standard as the remainder of the home and form a weathertight and stable addition to the house Integral garage Ensure that it is finished internally to a reasonable basic level of decoration, appropriate for its intended use. It is weathertight (not necessarily watertight, 100mm brick wall) and where abutting the house incorporates, a suitable cavity tray and flashing. Ensure firestopping is complete. Sound insulation - are RSD’s compliance certificates available - pre completion testing reports available from a UKAS or ANC member The following guarantees should be provided ‘where applicable’: - basement tanking, materials and workmanship insurance-backed 10-year guarantee - flat roof (including balconies and terraces), materials and workmanship insurance-backed 10-year guarantee - foundation underpinning insurance-backed 10-year guarantee - timber treatment, materials and workmanship insurance-backed 10-year guarantee - chemical injection damp-proofing, materials and workmanship insurance-backed 10-year guarantee - remedial wall tie replacement, materials and workmanship insurance - backed 10-year guarantee

169

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

14.6

Item of construction to be quality checked

Builder Check

ICW Inspect

Drainage All foul and surface water drainage should be connected, tested and fully operational. Where non-mains drainage is incorporated, it should be sited to allow suitable maintenance and emptying (as should filling any form of storage tank, i.e. oil). Ensure land drainage is present where necessary, i.e. waterlogging likely within 4m of the dwelling. Display robust notice plates indicating maintenance and operating requirements for non-mains drainage and oil fuel storage systems. Boundary, retaining or garden walls - to be complete and structurally stable. Paths, drives and patios - to be laid to reasonable, self-draining falls and suitable to take their intended loading, i.e. the weight of a tanker if storage or septic tanks are located too far from the highway. No path, patio or drive should be within 150mm of the dpc to the external wall of the house or garage. Level thresholds - should be suitably constructed to prevent damp ingress and allow adequate entry to the dwelling via a wheelchair Planting - ensure that any planting scheme introduced has been designed to suit the foundations already constructed Superstructure Ensure that all finishes are to a reasonable basic visual standard, the brickwork / rendering and roof covering is of a consistent nature in quality of finish and workmanship. All windows and door frames must be reasonably sealed where abutting the external envelope to prevent weather penetration. All rainwater goods must be in place and connected to the drainage system and all timber products are suitably treated / decorated to give a reasonable finish and protection against the elements.

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

170

14.6

Item of construction to be quality checked

Builder Check

ICW Inspect

External Walls: - rendering - should be durable and decorated to resist the weather and impact - should not bridge the dpc Masonry - should be matched in colour and texture providing reasonable aesthetics - joints should be filled / pointed and consistent - mortar should be durable and consistent in colouring - corbelling and / or plinths should not be excessive, thus enabling water to collect General - movement joints should be suitably located and filled - weepholes should be evident at all locations of cavity projections and at dpc level within timber frame construction - ensure that surfaces are reasonably plumb and level - lead flashings should be correctly located and fixed - dpc should not be bridged and located a min. 150mm above finished external ground level

171

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

14.6

Item of construction to be quality checked

Builder Check

ICW Inspect

Windows and Doors: - ensure that all windows and doors are: - suitably decorated to a reasonable visual standard and to provide weather protection to the home - designed in such a way to shed water from the external envelope - provided with a suitable deterrent against a forced entry - ensure that brickwork and stone cills and heads shed water and are not damaged / cracked Roofs: - all finishes (tiles, slates, lead or felt) should be free from damage, laid to falls, where appropriate, and finished to a basic visual standard - all rainwater goods should be in place laid to appropriate falls and connected to the drainage system - all fascias and soffits should be decorated to a basic visual finish and to protect them from the elements Chimneys and parapets - ensure that: - all cavity trays and flashings are correctly situated - the chimney is correctly sized for stability and located the correct height above pitch line - the cowling is correctly fitted (where applicable) - the masonry and the flaunching is correctly pointed

NB where there is a

in the ICW Inspect column, these items will be inspected where available to be seen at the time of inspection.

172

173

Conversion Guidance

15.0 Introduction Depending on the condition of the original building, an Expert survey is usually required for the elements below. If the Report concludes that any of these elements are unable to meet the life expectancy of 30 years for the structure and 10 years for non-structural elements, they should be systematically replaced or repaired. The main report may be made up of several individual reports, such as and Engineer’s report on foundations and a specialist company report on rising damp and/or timber treatment.

Additional Guidance on International Construction Warranties Limited Requirements: •

All conversions must be registered with ICW prior to any building works commencing on site.

•

Your appointed surveyor is unable to inspect the development until we have received all the reports, plans specifications etc. and carried out a desktop appraisal.

•

Testing of reclaimed materials such as bricks, timbers, tiles, slates etc. maybe subject to a third-party test to show suitability.

•

All new structural timber must be stamped KD or DRY timber .

Retained Elements: •

Foundations and load-bearing structures, including floors, walls and roof.

•

Damp-proof courses and membranes*.

•

Timber treatment against insect and fungal attack*.

•

Roof coverings.

•

Weather resistance of walls including claddings, render, re-pointing etc.

•

External doors and windows. Existing single glazed windows must be replaced with suitable double-glazed units or an endorsement will be added to the policy to exclude the from cover.

•

External and internal services.

•

Drainage.

174

15.2

Guidance on Experts Reports for Retained Elements

Retained Timber

A full structural report of the existing building as described in BRE Digest 366 including:

•

All retained elements must be free from any rot/ decay/ insect infestation. If advised as per the structural survey or specialists’ recommendation, all timber should be treated accordingly, and an insurance backed guarantee provided.

•

They must be stress graded by an Expert prior to them being used.

•

A structural engineer must provide calculations to justify their adequacy.

•

Moisture content of the timbers must be provided to ensure they are adequate.

•

Foundations.

•

Any basement.

•

Suspended timber floors, including joist ends, wall plates and ventilation.

•

Ground bearing slabs.

•

External and internal walls, including lintels and any built-in timber.

•

Intermediate floors, including, for timber, the condition of any built-in joist ends, wall plates and floor coverings.

•

Any structural concrete (incl. carbonation) / steel frame.

•

Roof structures, including wall plates, joist ends, valley/parapet gutters.

•

Chimney and parapets.

•

Report on investigations regarding rising damp, insect infestation and fungal decay. The report should be complied by a suitably qualified expert (e.g. Certified Surveyors for Remedial Treatment).

•

Weather resistance of walls including claddings, render, re-pointing, parapets and chimney etc.

•

Report on any retained roof coverings, including adequacy of fixings from above and below.

•

External doors and windows.

175

Green Timber/ Ungraded Timbers •

The use of green timber/ ungraded timbers are not permitted as structural members e.g. lintels, beams, joists, rafters, purling etc., nor where they are aesthetic elements but are “fixed” to the structure, as the extent of their shrinkage is unknown and can lead to structural damage of the property.

*In addition to the installer guarantee, the builder is required to provide a 10-year insurance backed guarantee: •

For chemical damp-proof course and basement tanking.

•

Timber treatment against insect and fungal attack.

•

Specialist roofing systems.

•

Proprietary externally applied weatherproofing and/or insulation systems.

•

The report should identify those parts of the building that have not been fully inspected at the time of the survey.

•

Suitable experts, with relevant experience, normally include: Registered Architects, Chartered Civil and Structural Engineers, Charted Building Surveyors, Members of the Chartered Institute of Building orMembers of the Association of Building Engineers.

15.1 Assessment Process Conversion / Refurbishment / Re-build Assessment We will always need to carry out a technical assessment of your property before we can agree to register it for cover under our warranty policy scheme. The assessment is not just a desktop overview of your proposal and specification of the project but will also be subject to our initial site visit. We understand that you need to make quick progress on site, in order to help you to do this we set out below how we can help each other to streamline the assessment process.

However, on larger projects it may be more practical for reports to be received by us on later stages of the building as was work proceeds. If this is the case, please mention it when you first register the project. This will save unnecessary questions and delay later.

What Remedial Works We Expect •

Any roof covering that is not in sound condition should be replaced. If you propose to retain any roof coverings, we will need safe access so we can inspect both above any below the covering. This safe access will also be needed by your expert for their report.

•

All external walls must prevent moisture penetration to the inside and be insulated to building regulation requirements. This can be achieved where walls are “drylined” with a suitable independent system, which will both insulate the fabric and prevent moisture ingress, or by the provisions of an externally applied render/ insulation system.

What are we looking for? In order to understand your project, we need to know as much a possible about it as soon as possible. In particular, we need to see your: •

Project specification – existing drawings, proposed drawings, remedial proposals, plans and specifications (Scope of Works)

•

Structural engineers report – to comment on structural adequacy of retained elements and confirm life expectance of at least 30 years

•

Any habitable areas either below or partially below ground level must be provided with a minimum grade 3 tanking system or equivalent.

•

Experts reports – these will be in addition to the structural engineers reports on rising damp, timber infestation and fungal attack (see guidance on reports later in this document).

•

All repairs and treatments identified in expert’s and engineer’s reports.

•

In addition to the contractors guarantee, min 10-year insurance backed guarantees are required for chemical dpc’s, underground tanking systems, timber treatments for insect and fungal attack, specialist roofing systems and proprietary externally applied weather proofing/insulation systems. Rising damp and timber treatments must be carried out by a BWPDA member.

•

High value cases will also require additional information i.e. Site investigation reports, Geotechnical surveys and design & access statements

By providing us with the correct information when you notify us of the proposed development, we will be able to complete our desktop overview and arrange a site visit in a much quicker time period. Ideally the inspections for all the experts/specialist reports should be carried out when all the relevant parts of the building are opened. Existing plaster and other redundant elements should have been removed e.g. at the “SOFT STRIP” stage. This will enable us to confirm our initial acceptance of the scheme. 176

15.2 Substructure Foundations

•

Pile and beam

An appraisal of the existing building and its foundation should be carried out by a Structural Engineer or similarly approved expert by International Construction Warranties Limited.

•

Pier and beam

•

Proprietary underpinning methods

This appraisal should address such items as settlement, heave, foundation depth and type, soil type, radon and contamination, basement walls and floors and trees adjacent to buildings. When carrying out the appraisal the person should consider the proposed increased loading on the structure and foundations, alterations to existing load paths and any alterations to the existing stability of the building. Where it is proposed to use the existing foundations, International Construction Warranties Limited should be consulted at the design stage. Providing the building shows no sign of movement and the proposals do not increase the loading on the foundations International Construction Warranties will accept the existing footings. Trial holes should be dug to ascertain the extent of the foundation and make-up of the sub-soil. Where the existing foundations are inadequate or the building has moved/cracked and/or the proposals are to increase the load on the footings, a qualified engineer should design a suitable solution. The proposed solution must be sent to International Construction Warranties Limited as part of the required information prior to quotation. When it is necessary to underpin a building, this is covered under the Building Regulations and an application should be made to the Building Control Authority and work inspection by them. Proposals for underpinning should be prepared by an Expert and be in accordance with BS 8004 or a proprietary underpinning system. Underpinning involves extending the foundations downwards in order that the building bears on to move stable ground. There are several ways to achieving this and these include: •

Traditional mass concrete

•

Angle pile

177

The decision as to which system should be used depends on several factors, including the type of existing foundation, depth of suitable strata, and position of water table.

Traditional Underpinning Sequence of underpinning to be carried out in accordance with the approved plans (generally, alternate bay sequence). Refer to diagram below. Where a bay is located at a wall intersection or return, at least 600mm of the intersecting wall or return should be underpinned at the same time. Maximum bay length not to exceed 1.0 metre reduce to 0.7m if the brickwork is poor quality. Excavations to be properly bottomed and de-watered. Size of new foundation to be appropriate for the safe bearing capacity of the supporting sub-soil.

15.2

Angle Pile

•

Determine the position of water table

The stabilization of an existing wall foundation using pairs of piles installed at an angle, through drilled holes in the existing foundation.

•

Assess the drainage characteristics of soil

•

Select an acceptable construction type, this will probably be one of the following:

Pile and Beam The stabilization of an existing wall foundation by the installation of Mini Piles in pairs, one as a tension pile, one as a compression pile, connected by a reinforced concrete or concrete encased steel needle beam supporting the wall.

Pier and Beam The stabilization of an existing wall foundation by the installation of a series of Piers connected to the existing wall by reinforced concrete tee beam and connected with a longitudinal ground beam to provide lateral restraint.

Tanking – Basement Space If the building has an existing basement or it is proposed to build a new basement it is important that International Construction Warranties Limited are consulted at the design stage to discuss and agree the proposals. The designer should identify the intended use of the basement as this has a bearing on its design and construction. Where it is intended that any accommodation below ground level is to be habitable, then the design should be such that no moisture/damp should enter this area/ there are a number of possible solutions to tanking existing basements and guidance is given in BRE Good Building Guide 3- Damp Proofing Existing Basements. Additional information is provided in Approved Document – Basements Design, which although covers design of new basements, identifies several key points. Which are applicable to the design of all basements this includes:

•

Mastic asphalt

•

Cementitious render

•

Self-adhesive membranes

•

Liquid applied membrane

Products which are used should have independent third-party certificates acceptable to International Construction Warranties Limited and, where required, should be installed by an approved installer.

The following are examples of different types of tanking systems. However, the installations must be applied strictly in accordance with the manufacturer’s recommendations:

Mastic Asphalt Method: Build up a 2-coat asphalt angle fillet at wall/floor and wall/wall junctions. Apply 3 coats of asphalt to total of 30mm on floor slab and 20mm to walls. Joints between successive coats should be staggered by at least 150mm (floors) and 75mm (walls). Add 50mm protective sand/cement screed and reinforced concrete loading, coat. Build a vertical masonry lining wall (loading coat), backfilling progressively against the asphalt with a 40mm cement/sand mix.

Cementitious Render or Cementitious Compound Method: Apply a cement corner fillet at wall/floor and wall/wall junctions. Render: apply three coats of the proprietary mix. Lap coats in accordance with the render manufacturer’s instructions and cure. Skim-plaster walls if necessary. Compound: damp substrate, apply two coats to manufacturer’s recommendations, followed by a loading coat and floor screed. 178

15.2

Self –Adhesive Membrane Method: add wall/floor and wall/wall fillets. Secure the membrane to the dry wall and floor surfaces following the manufacturer’s guidance allowing at least 150mm overlap at joint. Protect the floor membrane and build up blockwork lining wall, progressively backfilling with 18mm layer of cement/ sand mortar. Add a new floor screed of at least 50mm thickness and re-plaster.

Liquid- Applied Membrane Method: this system will normally be one of the following: bitumen emulsions and solutions, rubber latex polyurethane compounds, epoxy resins. Usually one or more liquid coats are applied which require a period of cure before laying of a new floor screed and construction of a new inner leaf (normally backfilled with cement/sand mortar). Protect the floor membrane from damage during building operations.

problem, consideration should be given to the removal of the chimney breasts in the basement and providing adequate support at ground level to the retained chimney. Maintain continuity of the tanking system by continuing into the reveals of openings. Continuity of the tanking system is maintained where service pipes pass through the tanking. Where the basement area is to be non-habitable, such as storage, it should be designed to ensure that the area is (Grade 2) reasonably dry and well ventilated. This is of particular importance where timber is present in order to prevent the outbreak of wet/ dry rot in the building. The measures to ensure that the storage areas are reasonably dry are not as onerous as when designing a habitable basement, guidance on ventilation on non-habitable areas is shown in table 4.1.

Existing basement floors may be suitable if it can be shown the slab is of an adequate thickness, usually in the region of 100mm, and is bearing on to a suitable inert hardcore. The proposals to tank the basement should address both the walls and the floor, in order to ensure the integrity of the basement area.

Type of Floor

Minimum ventilation per metre run

Timber

3000mm2

Concrete

600mm2*

Note: *Building Control Authorities may require higher standards

It may also be necessary to provide land drainage to the external perimeter of the basement in order to reduce hydrostatic pressure to acceptable levels (consult the Building Control Authority who may have local knowledge of water table conditions). Internal walls will also require tanking if either they do not have an effective dpc located at the same level as the floor tanking membrane, or if they link with an external wall which is in contact with the adjacent ground. Wall tanking should extend at least 150mm above adjacent ground levels. Where the adjacent ground is retained to the full height of the wall, the wall tanking should overlap the wall dpc located above ground level. Built-in structural timbers such as timber lintels shall be replaced (e.g. with concrete lintels) if they are sealed by tanking. Ensure continuity of tanking is maintained around chimney breasts. To simplify the 179

Prevent conditions of damp that may cause decay or failure of materials such as timber, insulation and reinforced concrete: •

Remove excessive condensation trapped within fabric of the building.

•

Prevent the build-up of gases escaping from ground or leaking gas pipes.

15.2

Detailed guidance on waterproofing basements is contained in the following:

•

Rubble filled walls.

•

BRE Good Building Guide 3 – Damp proofing existing basements.

•

Random flint/granite walls or other similar impermeable materials.

•

Approved Document - Basements for dwellings.

•

Mud walls (Cob), wattle and daub.

•

BS 8102 Code of Practise for Protection of Structures against water from the ground.

•

Rat trap bond.

•

British Cement Association Basement Waterproofing Design Guide.

British Cement Association Basement Waterproofing Site Guide

Damp-Proofing An insurance backed guarantee to the satisfaction of International Construction Warranties Limited shall be provided for all injected chemical damp proof courses. A suitable damp-proof course should be provided to existing walls and be placed at least 150mm above external ground level to ensure that ground moisture does not enter the inside of the building. An existing damp proof course needs to be installed in an existing wall there are two options available: •

Injected chemical damp proof courses.

•

Physically cutting a new damp proof course.

Injected chemical damp proof courses shall be installed by a registered member of the British Wood Preserving & Damp-proofing Association (who will provide a 10-year underwritten guarantee) and be in accordance with BS 6576 Code of Practise for Installation of Chemical Damp-proof Courses.

Most types of wall are suitable for the treatment by a remedial damp-proof course system. There are exceptions to this and include: •

Walls of exceptional thickness i.e. greater that 60mm.

Advice should be sought from the specialist installer as to the suitability of their products/systems. Products used in chemically injected systems shall always hold a current independent third-party certificate acceptable to International Construction Warranties Limited. Provision can be made for physically cutting in a new damp-proof course. The drawback is that they must be mechanically inserted into brickwork or coursed stonework. Random flint walls, rubble in-filled or in unusually thick walls may therefore require some rebuilding. When cutting into the walls to install the dpc it is essential to ensure that all pipes and wiring have been moved out of the way. The new dpc should be linked to any membrane beneath a solid concrete floor or turned down the wall to protect timber and joist ends.

Location of Damp-Proof Courses and Membranes It is essential that any new damp-proof courses are continuous with other damp-proof courses and membranes to provide an effective barrier against rising damp. Damp-proofing courses should be located in a manner that damp susceptible materials such as suspended timber floors, joist ends, and wall plates are located within a dry zone of the wall construction. Continuity of injected damp proof courses should be maintained at changes in floor levels, around chimneys and fireplaces, within recesses, alcoves, party walls, garden walls, etc. Often in rehabilitation work it is not possible to lower ground levels adjacent to walls, as this will reduce the depth or cover to foundation and footings. In cases where the ground level is higher than the adjacent floor level special attention is required to maintain continuity of the damp proofing system. 180

15.2

Further guidance on damp-proof is available: •

BRE Digest 245 Rising Damp in Walls.

•

BRE Good repair Guide 5: Diagnosing the causes of damp.

•

British Wood Preserving and Damp proofing Association.

•

Independent third-party certificates acceptable to International Construction Warranties.

The root cause of fungal attack is dampness. For example, dampness may be caused by the following: •

Rain penetration.

•

Condensation.

•

Hygroscopic salts.

•

Defective rainwater goods and roofs.

•

Bridging of existing dpcs, or no dpc.

Treatments of Timbers- Rot/Insects

•

Defective renders.

Any remedial treatments shall be carried out by registered members of the British Wood Preserving and Damp-proofing Association in accordance with their Code of Practise of Remedial Treatment and associated technical leaflets. A 10-year insurance backed guarantee shall also be provided.

•

Direct penetration of rainwater through solid walls, particularly those facing prevailing winds.

•

Leaking drains and internal plumbing.

•

Incorrect external levels.

In order to obtain insurance, it is necessary to undertake a detailed investigation of all timber members to identify the presence of any insect or fungal decay and treat the affected areas as appropriate. It is essential that the type of fungal attack is correctly identified as treatment methods vary for dry rot and wet rot.

Fungal attack covers wet rot and dry rot. Wood rotting fungi can be divided into two categories according to their effects on the wood: •

Brown Rot- causes the wood to become darker in colour and crack along and across the grain when dry. Badly decayed wood will crumble to dust, and most wet rots and dry rot fall within this group.

•

White rot – the wood becomes lighter in colour and the wood cracks along the grain. All white rots are wet rot.

•

Insects attack included Common Furniture, Death Watch, House Longhorn and Powder Post Beetle.

181

Fungal attack is controlled by two sets of measures, primary and secondary. Areas which have not been inspected should be clearly identified to enable a subsequent inspection to be carried out when the structure has been fully exposed; this could include rafter feet and wall plates which are partially prone to rot. Primary measures consist of locating and eliminating sources of dampness and promoting the rapid drying out of the structure. Where the timber becomes wet and remains wet e.g. the moisture content exceeds 20%, then it is likely to decay, and by eliminating the source of dampness and drying of timbers below 20%, the fungus will normally stop growing and will eventually die.

15.2

Secondary measures consist of determining the full extent of the outbreak then either: •

Removing all decayed timbers.

•

Treating of walls to contain fungi within the wall (only applicable to dry rot).

•

Treating of sound timbers with preservative where required.

•

Using preservative-treated replacement timbers (pre-treated).

•

Introducing support measures such as isolating timbers from walls and provision of ventilation between timbers and the walls.

•

Appoint a specialist company who can provide automatic building monitoring systems. Timber identified as being at risk of decay (such as lintels, joist ends, flat roof timbers, rafter feet, etc.), can be monitored and any changes in moisture content recorded by a central computer and the appropriate action taken before serious damage occurs.

Floors Dry rot commonly occurs when timber is in contact with damp brickwork and where ventilation and heating are inadequate. Therefore, particular attention should be paid to cellars, basements and sub-floors and also behind panelling.

Existing Concrete Floors Where there is an existing concrete ground floor and this is to remain, the following should be identified: •

The thickness and condition of the existing slab, a minimum of 100mm concrete is normally expected. Slabs less than 100mm are more likely to be vulnerable to rising damp, especially if the concrete is of poor quality.

•

If there are proposals to increase the load on the existing slab, such as building a masonry wall, the new wall should be built on adequate calculations.

•

Are there any gaps between the skirting and floor suggesting settlement of the slab; is the fill beneath the slab over 600mm?

•

Are there any cracks in the in the floor due to settlement?

•

If the slab has settled it may be practical to re-level the floor with a new screed or self-levelling compound. Before undertaking any works to a slab which has settled, it must be ascertained that the settlement has stopped.

•

Has the slab heaved due to either sulphate attack or clay swelling? Concrete ground floor slabs are vulnerable to attack by water soluble sulphates present in the hardcore, e.g. colliery shale. Where the slab has lifted and is no longer in contact with the hardcore, sulphate attack is the most probable cause. When the slab lifts it causes the walls containing the slab to be pushed out.

Clay heave can be attributed to the swelling of the clay subsoil when there is a recovery of the desiccated zone following the removal of a tree. The amount of heave can be as much as 150mm. This swelling of the clay forces the ground floor slab upwards and can also push out the walls. Where a slab has heaved, further investigation is necessary to determine the reason for this and appropriate measured taken to rectify the cause and damage. Guidance on this subject matter is available in BRE Good Building Guide 28 domestic floors. Where it can be shown that the existing ground floor is structurally adequate but does not incorporate a damp proof membrane, a damp proof membrane may be laid over the existing slab e.g. 2/3 coat bitumen paint or 1200 gauge (300μm) Polythene over which a minimum 50mm 1:3 screed should be laid (65mm minimum thickness in the case of floating screeds and incorporating d49, chicken wire mesh reinforcement). The damp proof membrane should lap with the damp proof course.

182

15.2

Existing Suspended Timber Floors Where it is proposed to keep the existing ground floor, the following guidance should be followed: •

The existing floorboards/finish should be lifted to ascertain the condition of the timber joists, wall plates and report carried out by a specialist relating to the insect infestation and fungal attack.

Timber joists which were previously built into walls and the joist ends have decayed can be isolated from the damp walls by cutting back the joist and supporting on joist hangers. If the decay extends beyond the proposed cuts for the joist hangers, then the timber can be replaced. This repair method is should only be used where not more than three joists are affected per floor zone and the joist depth being not less than 140mm, unless designed by an Expert.

When deciding if an existing ground floor is adequate, there are several areas which should be addressed, these include:

There are also proprietary methods of splicing new timbers to existing joists with galvanised plates; these systems are an acceptable method of repairing rotten or damaged joists.

•

An adequate DPC to walls/sleeper walls.

Radon and Contamination

•

Are all timbers free from rot and insect infestation? Particular attention should be given to the ends of the joists and wall plates.

•

Adequate ventilation to the subfloor, (1500mm2 of free opening in air bricks per metre run of wall, in older properties where there is no oversite (subfloor) this figure should be doubled).

•

Adequate foundations supporting sleep walls.

•

Joists are of sufficient size and span.

•

Are any load-bearing internal walls build off floor joists.

•

Have joists been weakened by excessive notching or drilling.

•

Adequate trimming to hearth.

•

Strutting of joists with spans in excess of 2.5m.

The surface of the oversite covering should be above the highest level of adjoining ground or laid to fall with a drainage outlet above the lowest level of the adjoining ground and the outlet screened against rodent entry. All sub-floors voids should be cleared of all timber/builder’s rubble as this can provide a ready source of food for dry rot and insects.

183

The aim is to improve the resistance to contaminants and moisture as much as possible, but it has been recognised that this is not always practical. In arriving at an appropriate balance between historic building conservation and improving resistance to contaminations and moisture the advice of the local planning authority’s conservation officer should be sought at an early stage in the design process.

New Concrete Floors Replacement ground floor slabs should: •

Be minimum 100mm thick and preferably located 150mm above the adjacent ground levels.

•

Incorporate below the screed and lapped to form and integral barrier with the adjacent wall dpc.

•

Be laid on a minimum 100mm consolidated and well graded non-organic hardcore. Hardcore which is used must be free from water-soluble sulphates and other deleterious materials. Outbreaks of dry rot have been recorded and attributed to hardcore containing pieces of wood infected with dry rot.

In cases where the finished slab level is substantially higher than the damp-proof course level in the wall, special attention is needed to ensure that damp does not bridge over the dpc.

15.3 Superstructure Drainage

General

Where it is intended to use the existing below ground foul drainage system a CCTV survey should be carried out to ascertain the condition of the drains and manholes. The survey should cover size, type of drain, falls and its adequacy to take the proposed discharge. An air or water test could also be carried out.

Prior to undertaking structural repairs, it is essential that the root cause of the structural defect has been remedied e.g. by underpinning, addition of adequate lateral restraint, buttressing, etc. strengthening works to the structure may also be necessary to accommodate increased or modified loads.

The use of existing surface water drainage may be acceptable providing that it can be shown to be carrying the water away from the building i.e. to a soakaway located 5m away, public sewer etc. A CCTV survey should be carried out.

Masonry Walls

Drainage and Ground Services Excavations for new drains and below ground services should not extend below the spread load line of foundations unless special precautions are taken such as protecting the drains/service installations from damage by backfilling trenches with concrete whilst maintaining flexibility of the drainage system to accommodate movement. Often with rehabilitation work it is necessary to extend the drainage system to connect to additional sanitary accommodation. Slab levels and drain inverts are fixed and consequently insufficient cover may be provided to the extended drain. The manufacturer’s recommendations for protection should be followed.

When damage has occurred to walls, the cause needs to be investigated. Likely reasons for the damage include: •

Ground movement – foundation failure, settlement, subsidence, chemical attack..

•

Thermal Movement – thermal expansion of wall due to temperature changes.

•

Roof Spread – pitched roofs not properly tied, spreading at eaves.

•

External and internal walls not bonded together.

•

Wall tie corrosion.

•

Lintels inadequate over openings.

•

Sulphate attack – water soluble sulphates attack cement-based mortar, normally in a wet environment, i.e. below ground level and parapet walls.

•

Frost attack.

•

Bonding timbers present and subject to rot and shrinkage.

•

Ineffective or no lateral support at floor and roof level.

•

Moisture ingress.

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15.3

Cracking in Masonry Walls Minor cracking can be defined as cracking which occurs in the mortar joints and which does not extend through the masonry components. Providing that the crack is not wider than 4mm and there has been no lateral displacement of the wall, the wall can be repointed. Minor cracking does not usually affect the structural integrity of the wall and may be remedied by raking out mortar joints of the wall and may be remedied by raking out mortar joints to a minimum depth of 15mm and repoint with a mix 1:2:9 Cement : Lime : Sand. If the existing mortar is very weak use a 1:3:12 mix. Major cracking affects the structural integrity of the wall and investigation should be undertaken to find the cause of the problem. If it is necessary, cut out the brickwork either side of the crack (minimum 225mm) and replace, ensuring that adequate bonding is maintained between new and existing brickwork. It is recommended that brickwork reinforcement is used within the new mortar joints. Avoid strong mortar mixes and use well graded sand to minimise shrinkage. The use of gun-applied mortar pointing system should be considered, as they are able to match strength and colour of the existing wall. Where repointing a wall or building a new wall, jointing should be ‘bucket handle’ or ‘weathered’ in preferenceto flush jointing. Recessed pointing is not acceptable (See diagram below).

185

15.3

Bucket Handle (Preferred)

Weathered (Preferred)

Flush Pointed

Recessed (on for cavity walls on sheltered sites)

Flush Pointed

Header Bond

Flemish Bond

Flemish Garden Wall Bond

English Bond

English Garden Wall Bond

186

15.3

Walls Out of Plumb/Bulging

Lateral Restraint at Roof Level

Where walls are more than 25mm out of plumb or bulge more than 10mm within a storey height a structural engineer should comment on the stability. The wall may need to be rebuilt or strengthening works undertaken. Where it is intended to provide buttressing walls to support off plumb and/or bulging walls, they should be designed by an engineer. In raised tie roofs (where no ceiling ties are provided at eaves level) lateral spread of the brickwork just below eaves level may have occurred because the roof has deflected. In such cases it is necessary to prop the roof and to rebuild the affected part of the wall.

The solution is to use retro-straps system, fitting solid noggins between the first three rafters and mechanically or resin bonding the strap to the wall and screwing it to the noggins.

Lateral Support at Floor and Roof Level Buildings may show signs of insufficient lateral support through bulging of walls. Many older houses are built with the floors spanning between the front and back walls with a load bearing spine wall and there is no lateral support to the flank walls floor or roof level. To overcome this, metal rods running through the building at floor and roof level, pulling together with end restraint nuts, can be fitted. This method is still acceptable, but due to the disruption involved as the tie will have to pass through every joist, it is more practical to apply the following system.

Other methods of achieving the acquired lateral supports are available and these include self-tapping tie bars, this system is suitable for tying the walls to floor joists only. 187

Further guidance is available within the BRE Good Building Guide 29: connecting walls to floors.

Bonding Timbers These are common on Georgian buildings and were laid in the internal skin of the wall to reinforce it and to provide fixings for panelling, etc. With the low compressive strength of lime mortar and general timber decay, the bond timber compresses under load. As the timber is on the inner skin, the compression causes bulging outwards. This may be apparent on the external face. Normally bond timbers should be exposed during the conversion and removed in short lengths and replaced with bonded masonry.

External and Internal Walls Not Bonded Together A common defect in properties up to the 1920s is the lack of bonding/tie of party walls to the external wall. Different bricks and bricklayers were often used, with the poorer quality materials and labour being used on the party walls. This junction should be exposed when undertaking a conversion and if the bond is inadequate suitable stitching detail incorporated.

15.3

Arches and Lintels

Wall Tie Corrosion

Where existing timber lintels support structural walls and it can be shown that the lintel is adequate for its purpose, i.e. there is no sign of any structural movement, loads will not be increased and the timbers are free from rot and insect infestation, this lintel can be retained. In order to ensure that a lintel is free from rot, a percentage of all lintels should be exposed at both ends and on the outer face for openings in external walls. International Construction Warranties Limited should be consulted to determine a suitable percentage of lintels to be exposed. Where movement has occurred and the timber lintel is inadequate, the lintel should be replaced with either a concrete or steel lintel and have the appropriate bearing. Consideration may be given to replacing timber with timber and calculations should be provided to justify this.

Cavity walls have been constructed since 1850, but it was not until 1920 that this form of construction was widely adopted. It is important when undertaking a conversion to confirm the construction of the external wall. Care should be taken, where headers are incorporated into the bond if the external brickwork, you should investigate the construction, as many properties in the Victorian period were built with either a 215mm outer leaf and cavity behind, or a 215mm inner leaf, cavity and half brick outer leaf with snapped headers. Where the wall is of cavity form, a survey of the wall ties on a percentage of the development should be carried out. An initial survey can involve cutting out bricks to inspect the condition and predicted (remaining) life span of the ties. During opening up works the ties can be inspected for their suitability and acceptance by International Construction Warranties Limited. Initial evidence of cavity wall failure can include cracking of bed joints in mortar. This is due to the expansion of the wall tie as it corrodes. Bulging of the external leaf could indicate that the ties have failed. Where there is wall tie corrosion or inadequate ties, a specialist company should be employed to provide a report which includes measures to overcome these defects. Where wall ties have corroded to an extent that it is serious enough to threaten the stability of the wall or building, a structural engineer should be appointed to determine the necessary remedial works.

One solution to this, is where new timber lintels are provided over openings, additional structural support can be provided by a concealed steel angle so that the timber lintels acts as a non- structural element. Where cracking has occurred in masonry arches (openings not supported by a lintel), then it will be necessary to prop the wall and rebuild the arched construction. In cases where failure has occurred due to the low pitch of the arch, it may be necessary to incorporate a lintel.

New Masonry Masonry walls should be built off a suitable foundation, incorporate a dpc and be in accordance with Approved Document A (E&W) and Regulation 11 (Scotland), up to three storeys. When a wall is outside the scope of these documents, a qualified Structural Engineer should design the element.

188

15.3

Existing Masonry

Impervious Sheet and Drained Sheet Systems

Where a wall is adequately founded or supported on a beam which shows no signs of distress, it can remain providing there is no increase in load onto the wall. Any increase in load should be justified by calculation.

Systems to prevent water penetration should be installed in accordance with the manufacture’s recommendations and shall possess third party accreditation acceptable to International Construction Warranties Limited.

However, masonry supported on timber beams should be avoided.

New Studwork

In older properties it is possible that Flitch beams and Bressumers may be supported masonry walls and these should be examined by an appropriate Expert to ascertain its capabilities to carry the load onto the wall. Any increase in load should be justified by calculation.

Studwork should be in accordance with current Building Regulations at the specific time of construction.

Existing solid brick or stone walls may be acceptable as a weather resisting wall subject to the exposure category of the building (see exposure to wind driven rain map page 81 and the porosity of the masonry. It is anticipated that all buildings located in severe or very severe locations will require a specialist’s report to identify the extent of any necessary remedial treatment.

Existing Studwork Many properties before 1880, have trussed internal partitions, usually located approximately halfway back in the depth of the property. Often these walls are load bearing and continue up through the building and carry floor and roof loads on the foundations.

The specialist report including the proposed design and/or the manufacturer’s details must be forwarded to International Construction Warranties Limited for approval along with the other requested reports that form part of the conditions placed on the warranty.

If a timber partition is load bearing, provided it is adequate and the loads are not being increased and the timber is free from rot and insect infestation, the partition can remain. Where there are defects i.e. the floor sags on the line of the partitions and there is distortion of door heads then additional strengthening works should be undertaken.

If the above situations cannot be satisfied, then a new external cladding or render system will need to be installed.

New door openings cut into an existing trussed partition should be overseen by a qualified structural engineer, as it can adversely affect the triangulation of the truss.

Independent Metal or Timber Framed Systems These should not be fixed to the existing masonry walls but fixed at the “head and base” to avoid direct contact. Ventilation should be provided to avoid build-up of condensation between the masonry and the inner lining system.

189

15.3

Timber Floors above Ground Level Existing timber floor joists can be retained within the building providing that they are adequate for their purpose. The following points should be considered: •

Joists are of sufficient size for the span.

•

Load on the floor is not being increased.

•

Have joists been weakened by excessive notching and/or drilling.

•

Ends of joists free from rot.

•

All timbers to be treated for insect infestation and wood rot.

•

No masonry walls are built off timber joists.

•

Adequate trimming to hearth.

•

Solid strutting or herringbone.

Where the existing joists do not comply with the span tables on page 191, but can be shown that the joists are adequate, in that there has been no floor deflection, International Construction Warranties Limited will consider these to be acceptable.

Timber Floors A common defect in floor joists is that the ends which are built into solid external walls have often rotted. A percentage of all existing joists should be examined to ascertain if there is any rot in timbers. Where timber rot is identified in these joists, then further investigation should be undertaken on a further percentage of the joists. A system of dealing with the rotten joists should then be implemented: •

Before carrying out this type of work, you should consult a qualified structural engineer to ensure the structural integrity of the building is not compromised.

•

Proprietary methods of splicing new timbers to existing joists with galvanised plates is also an acceptable method of repair.

•

Where the joists have been previously excessively notched to accommodate services then they should be strengthened by the addition of steel plates securely connected to joists.

Movement Joists between New and Existing Construction In order to avoid the damage resulting from differential movement between new and existing work, it is necessary to isolate the new extension from the existing construction whilst at the same time maintaining lateral support to the new construction and ensuring a weather tight joint, the isolation joint should extend through the foundations.

Walls of Special Construction If it is intended to retain walls of special construction such as wattle and daub, tudor, mud walls (cob) etc, they should be altered so as to form a non-structural element e.g. by the incorporation of an additional load bearing wall or framing which provides lateral support to the wall and supports all structural loads previously supported by the wall. It is also necessary to ensure that the wall provides an adequate barrier to the passage of rainwater into the fabric or the inside of the building. This may be achieved by e.g. the formation of cavity construction whereby the special wall forms the external leaf and the cavity construction provides the required resistance to rainwater penetration. It is recommended that expert advice is obtained for these types of construction.

Alternations to Existing Openings Where existing openings are to be filled with masonry, the new work should be adequately bonded to the existing; the weather resistance of the wall maintained and, if a party wall, comply with the requirements for sounds installation. Often it is necessary to make minor modifications to existing openings in order to accommodate new frames. In such cases the length of bearing of the supporting lintels should be verified and where less than 150mm the lintel may have to be replaced. 190

15.3

Floor Joists Permissible clear span between supports with imposed loads of 1.5kN/m2. Dead load more than 0.25 but not more than 0.50kN/m2 Sizes with No Partitions

Sizes with l/w3 Partitions Spacing of Joists (mm)

Spacing of Joists (mm)

Size of Joist mm x mm

C242 400

450

600

400

450

600

C242 400

Maximum Clear Span of Floor Joist (m)

400

600

400

450

600

Maximum Clear Span of Floor Joist (m)

47 x 72

1.27

1.15

0.89

1.35

1.27

1.10

47 x 72

1.15

1.04

0.80

1.21

1.14

0.99

47 x 97

1.92

1.82

1.46

1.03

1.92

1.68

47 x 97

1.73

1.64

1.31

1.82

1.73

1.51

47 x 122

2.55

2.45

2.09

2.65

2.55

2.29

47 x 122

2.29

2.21

1.88

2.39

2.29

2.06

47 x 147

3.06

2.95

2.61

3.18

3.06

2.78

47 x 147

2.76

2.65

2.35

2.87

2.76

2.50

47 x 170

3.53

3.40

2.99

3.67

3.54

3.21

47 x 170

3.18

3.06

2.69

3.31

3.18

2.89

47 x 195

4.04

3.89

3.39

4.20

4.05

3.68

47 x 195

3.64

3.50

3.05

3.78

3.64

3.31

47 x 220

4.55

4.35

3.79

4.71

4.55

4.14

47 x 220

4.09

3.92

3.41

4.24

4.10

3.73

63 x 97

2.19

2.08

1.82

2.31

2.19

1.93

63 x 97

1.97

1.87

1.64

2.08

1.97

1.73

63 x 122

2.81

2.70

2.45

2.92

2.81

2.55

63 x 122

2.53

2.43

2.21

2.63

2.53

2.30

63 x 147

3.37

3.24

2.95

3.50

3.37

3.07

63 x 147

3.03

2.92

2.66

3.15

3.04

2.76

63 x 170

3.89

3.74

3.40

4.04

3.89

3.54

63 x 170

3.50

3.37

3.06

3.63

3.50

3.19

63 x 195

4.44

4.28

3.90

4.61

4.45

4.05

63 x 195

4.00

3.85

3.51

4.15

4.00

3.65

63 x 220

4.91

4.77

4.36

5.05

4.91

4.56

63 x 220

4.42

4.29

3.93

4.54

4.42

4.10

Notes:

Joists should be doubled up beneath baths and any other pointof concentrated load. Maximum partition load 0.8kN/m2 (eg timber framed stud partition). Non loadbearing partitions should be supported as shown in diagram 2.107 No notches in trimmer beam unless designed by an Expert.

Key:

191

C24 timber is approximately equivalent to SC4 grade timber.

Non loadbearing lightweight partitions (loading not greater than 0.8kN/m2 run)

15.3

Chimney Removal

Sounds Insulation

Imperial Brickwork – Metric Blockwork

The aim is to improve the sound insulation as much as possible it has been recognised that this is not always practical. Depending on the status of the building various alternatives are permitted. Please refer to Building Regulations Approved Document E.

Where it is intended to use this construction, attention should be made to ensure that the wall ties do not slope inwards towards the inner leaf. Conventional coursings 450mm centres vertically will not match as imperial bricks are bigger than metric. The use of proprietary ties should be considered.

Chimneys When removing chimney stacks, they should be taken down to below roof level and capped. Chimneys located on external walls should be ventilated to the external air at roof and base level. Where it is intended to re-use existing flues they should be tested for airtightness. Adequate support should be provided to chimneys after removal of chimney breasts. Cantilever slabs built into existing walls or corbelling should not be used. The design of any support should be justified by calculation.

Concrete/Steel Framed Structures Where the scheme involves converting a concrete or steel framed building into dwellings the following guidance is given.

An appraisal of the existing building should be carried out by a qualified Structural Engineer considering the proposals for the change of use, this will include: •

Condition of the structural frame including joints.

•

Proposal to increase loadings on the structure and foundations.

•

Alterations to existing load paths.

•

Alterations to stability systems.

•

Changes in environmental exposure.

•

Recommendations to cover additional reports, testing by specialists.

The floor loads on the building may decrease as they will now be for domestic use only, were previously they were for example, offices. International Construction Warranties Limited will accept a statement from a qualified Structural Engineer confirming, where appropriate, that the existing foundation design is acceptable for the new loads subject to the building showing no signs of distress i.e. movement, cracking etc. Where the intention is to increase the load on the existing structure e.g. by the introduction of an additional floor, then structural calculations should be provided to prove the adequacy of the building and foundations. When intending to retain existing chimneys: the adequacy of the masonry, the existing trays and flashings to resist moisture and retain structural stability should be confirmed by the Expert’s report.

192

15.3

Concrete Framed Buildings

High Alumina Cement Concrete (HACC)

Where the building is of concrete construction additional reports are needed for:

Where High Alumina Cement Concrete has been used in a building and the intentions are to keep the existing structure International Construction Warranties Limited may consider the property for warranty subject to:

•

Carbonation

•

Chlorination

•

The structure being free from obvious signs of deterioration.

•

The building being weather-tight.

•

Structural calculations being provided to show that the floors and roof can solely carry the loads imposed on them.

Carbonation involves a reaction of carbon dioxide in the air with the free lime present in the concrete. Over a period, this reduces the pH level of the concrete. With a reduction in the alkalinity, and the presence of both water and oxygen, corrosion of the embedded steel will occur.

•

Typically HACC precast concrete beams were cast as “X” or “I” shaped beams.

Visual surveys on concrete structures are a starting point to gather information. However, care should be taken as the concrete structure may not show any obvious signs of corrosion and yet corrosion of the reinforcement may be occurring. It is important that a second stage survey incorporates the following:

In addition to any structural reports a visual inspection of the steel frame should be carried out to assess the extent of any corrosion of the framework.

The two major causes of corrosion in concrete are carbonation in association with inadequate depth of cover to reinforcement and chlorine penetration due to de-icing salts and admixtures used to accelerate the setting and hardening of concrete in temperatures at or below freezing point.

•

Chemical tests on the concrete structure to ascertain if corrosion of the steelwork is or is likely to occur.

•

Depth of carbonation can be assessed either on site or in the laboratory and the depth of the reinforcement measured. This allows those areas of risk to be identified.

•

Chloride ion content can be taken by analysis of a drilled dust sample from the concrete.

Where concrete repairs are necessary, they should be carried out by a specialist contractor.

193

Steel Framed Buildings

Where corrosion is present accurate measurements can be made using an ultrasonic gauge. Data collected can then compare the thickness of steel sections against the original steelwork drawings, British Standards and Historical Structural Steelwork Handbook to ascertain if the structural frame is adequate for the proposed loads.

Concrete/Steel Frames When corrosion is apparent, what appears is a thick layer of rust e.g. 10mm only actually indicates a loss of between 1.9mm and 1.6mm of steel and it is therefore important to take readings. Exterior Steelwork - should be inspected. Where corrosion is visible, the steel can be grit blasted cleaned and recoated. Perimeter Steelwork- in direct contact with the outer leaf of the building can be prone to corrosion particularly in older properties. A sign indicating that this has happened is the displacement of the external masonry due to the expansion of the steelwork caused by corrosion. Corroded steelwork occupies between 6 and 10 times the original volume of steel the steel.

15.3

Perimeter steelwork - can normally be inspected during the conversion process and the appropriate repairs/replacement carried out. Interior Steelwork - normally corrosion of unprotected steelwork within the interior of a building is low with only superficial rusting. Providing a visual inspection confirms this and the environment intends to remain dry no further treatment of the steel will be required. Where the proposals involve the steelwork in a “wet” environment such as kitchens and bathrooms it should be adequately protected.

Bimetallic Corrosion This should be considered in the existing and proposed structure. Bimetallic corrosion occurs where two different metals are in electrical contact and are also bridged by water or water containing other chemicals to form an electrolyte, an electrical current pass through the solution from the base metal to the noble metal. Consequently, the noble metal remains protected and the base metal suffers increased corrosion. Where there is a possibility of this occurring or if it has already occurred advice should be taken from a specialist on how to deal with it.

Concrete/Steel Frames

Cast Iron, Wrought Iron and Mild Steel Structures

When corrosion is apparent, what appears is a thick layer of rust e.g. 10mm only actually indicates a loss of between 1.9mm and 1.6mm of steel and it is therefore important to take readings.

Many older buildings which are converted into dwellings e.g. warehouses, cotton, mills etc were built using cast iron, wrought iron or mild steel. Cast and wrought iron were first introduced in 1800’s followed by the use of steel around 1890. With the onset of steel, the use of cast and wrought iron declined.

Exterior Steelwork - should be inspected. Where corrosion is visible, the steel can be grit blasted cleaned and recoated. Perimeter Steelwork- in direct contact with the outer leaf of the building can be prone to corrosion particularly in older properties. A sign indicating that this has happened is the displacement of the external masonry due to the expansion of the steelwork caused by corrosion. Corroded steelwork occupies between 6 and 10 times the original volume of steel the steel. Perimeter steelwork - can normally be inspected during the conversion process and the appropriate repairs/replacement carried out. Interior Steelwork - normally corrosion of unprotected steelwork within the interior of a building is low with only superficial rusting. Providing a visual inspection confirms this and the environment intends to remain dry no further treatment of the steel will be required. Where the proposals involve the steelwork in a “wet” environment such as kitchens and bathrooms it should be adequately protected.

When the intention is to keep the existing structural elements, an appraisal of the existing building is necessary. In addition to this the engineer should comment on the following: •

Determine age of the building and materials used.

•

Assess how its constructed has faired.

•

Justify the loadings by calculation.

•

Identify areas where additional testing and/or opening is necessary.

If the proposed loads remain unchanged or reduced, as will probably be the case, and it can be shown that the existing structure had not suffered any deterioration due to corrosion, deflection of structural members etc; the building may only require localised structural alternations. When the intention is to increase loads, carry out major structural alterations, or the existing building is under designed, a structural engineer should comment on this and provide calculations to justify the proposals. 194

15.3

Filler Joist Floors

PRC Demolition and Rebuild

Many buildings of late Victorian and Edwardian period were built with floors constructed of clinker concrete supported by embedded iron or steel joists. The concrete produced with clinker aggregate was porous and therefore provided poor corrosion protection to the metal.

Where the PRC property is demolished to slab level International Construction Warranties Limited will consider the rebuild for warranty purposes subject to:

The clinker also contains particles of unburnt or partially burnt coke or coal which contains substantial proportions of sulphur. As the concrete is porous the sulphur oxidises to form sulphur dioxide (SO2) and if moisture is present this then forms sulphuric acid (H2SO4). Where floors have been subject to the weather for any length of time severe corrosion of the embedded iron or steelwork is likely to have occurred. When considering a conversion in a building which has filler joist floors it is important to firstly investigate to ascertain if the floors have been subject to damp conditions and whether any significate corrosions has taken place.

•

A structural engineer should comment on the adequacy of the existing foundations to take the proposed loads. Where it is necessary, the footing should be underpinned or a new foundation ‘stitched’ to the existing.

•

The existing slab should be examined for any signs of settlement, heave or sulphate attach and where appropriate trial holes cut into the slab to ascertain the thickness of concrete and the type of hardcore.

•

Any new load-bearing walls are to be built on foundations unless it can be justified by calculations that the existing slab can carry the load.

•

Where the existing below ground foul drainage system is retained a CCTV survey should be carried out.

PRC Repairs Particular attention should also be made during the conversion to ensure that the floor remains dry and this could include providing a temporary covering if removal of the existing roof is necessary. International Construction Warranties Limited will need to inspect the property prior to work commencing to comment on those elements which are being retained:

Surveying Roof Timbers All roof timbers should be surveyed by a specialist and any necessary treatment carried out. Particular attention should be given to rafter feet, wall plates and valley timbers as these often show signs of rot.

•

Ground floor slab – any signs of movement or damp.

Roof Structure

•

First floor joists – deflection of structural timbers, rot, adequate ventilation, insulation.

•

Drainage- external below ground drainage.

•

External – paths, drives, garden walls.

It is essential that the roof structure has adequate strength, stiffness and dimensional accuracy appropriate for the new roof covering. In many existing buildings the roof structure is inadequate to support roof loads and has suffered from excessive deflection. Often, the necessary remedial works are relatively simple and inexpensive. Common problems encountered include:

•

Services – gas, electricity, water etc.

•

Excessive spans of rafters, purlins, binder and ceiling joists.

•

Inadequate ties between rafters and ceiling ties.

•

Insufficient number of collar ties at purlin level.

Where any obvious defects are apparent in the retained structure they should be replaced or repaired. 195

15.3

•

Decay of rafter feet and valley beams.

•

Settlement of purlin supports.

•

Lateral spread of raised-tie roofs.

There are several solutions for strengthening roofs which include: •

Provision of diagonal struts supported on loadbearing walls to reduce effective spans of purlins.

•

Provision of additional purlins.

•

Inclusion of new binders and collars.

•

Strengthening of rafters at ceiling level in raised tie ceilings.

•

Additional ties to connect rafter feet to ceiling joists.

•

Splicing new timbers to rafter feet.

All strengthening work should be designed by an engineer. Additional supports are often required for a new water tanks in roof spaces. These should be located such that ceiling joists are not excessively loaded and the loads imposed are transmitted directly to supports.

Roof Coverings

Where the existing construction is close boarded and there are no provisions to strip the roof to felt and batten International Construction Warranties Limited will consider close boarding to be acceptable if: •

Subject to survey by an expert which must also consider the exposure level.

•

There are no signs of damp ingress into the roof void due to wind driven rain, snow or capillary action of moisture.

A specialist report will be required to confirm the adequacy of the existing roof coverings and if timber treatment is required. If the proposals are to replace the existing roof coverings, then a temporary roof must be erected to protect the building and prevent water ingress into it. Failure to do so can lead to the building becoming saturated and the risk of wet/dry rot occurring. Please note that if you do not provide a temporary covering, International Construction Warranties Limited may refuse to provide policy cover for the project. Adequate ventilation should be provided. Where it is intended to re-use existing roofing tiles or slates, they should have a life span of at least 15 years. Where replacement coverings are heavier than the existing coverings, the works are usually controlled under the Building Regulation and approval is required in respect of the strengthening works to the roof structure. In the case of replacement roof coverings where no extra load is incurred it may still be necessary to strengthen the roof structure if the roof has deflected.

Systematic replacement of all roof coverings, including associated support systems such as battens, felt, flat roof decking, fascia’s, soffits and flashings should be carried out, unless it can be shown that the existing roof covering is adequate. The existing roof covering will only be considered as adequate if it has been replaced in the last 15 years and must be subject to an Experts report. All roof coverings older than this should be replaced. Consideration of reusing slates/tiles will be given subject to the condition of them and we may request that these be tested by a specialist organisation. Fixing of slates, tiles, the condition of existing fixings e.g. nails and clips should be examined if the intention is to keep the roof covering. 196

15.3

Weather Resistance of Walls and Cladding

Internal Treatments

Existing solid brick or stone walls may be acceptable as a weather resisting wall subject to the exposure category of the building (see exposure to wind driven rain map page 81 and the porosity of the masonry. It is anticipated that all buildings located in severe or very severe locations will require at least one of the additional treatments noted below. However, all solid masonry wall situations will require a specialist’s report to identify the extent of any necessary remedial treatment.

An alternative to preventing moisture penetration by using externally applied claddings and renders is internally applied methods.

The specialist report including the proposed design and/or the manufacturer’s details must be forwarded to International Construction Warranties Limited for approval along with other requested reports that form part of the conditions placed on the warranty.

•

These should not be fixed to the existing masonry walls but fixed at the ‘head and base’ to avoid direct contact. Ventilation should be provided to avoid build-up of condensation between the masonry and the inner lining system.

•

Impervious sheet and drained sheet systems. Systems to prevent water penetration should be installed in accordance with the manufacturer’s recommendations and shall possess third party accreditation acceptable to International Construction Warranties Limited..

External Treatments Existing cladding can be retained if it can be shown that: •

The system is maintaining the integrity of the building.

•

It is adequately fixed and the expected life span of the fixings where appropriate is in excess of 15 years.

•

The cladding material is free from and defects.

•

Adequate provision for movement has been allowed.

If the above situations cannot be satisfied, then a new external cladding or rendering system will need to be installed.

Systems are available that are installed on the inside of existing walls to prevent moisture penetration reaching the internal accommodation. These include: Independent metal or timber framed systems.

Interstitial Condensation Vapour control layers may need to be incorporated on the warm side of the thermal insulation. Voids and cavities may also need to be ventilated.

Surface Condensation Under certain conditions the warmth from sunlight falling onto damp solid masonry wall can drive moisture inwards and form condensation on the outside of a vapour barrier.

Control of Damp Penetration Measures should be taken to ensure that thermal insulation in cavities does not encourage the passage of damp from the ground or from the exterior of the building to the inside of the building. 197

15.3

Thermal Insulation of Walls and Claddings

Rendering for Conversion/Refurbishment

Various methods exist to upgrade the thermal insulation of existing walls and floors. Regardless of the methods adopted, it is essential that risks associated with increased thermal insulation are minimised, including:

Where the condition and bond of the existing render can be shown to be adequate it can remain subject to the following exceptions: •

If the render bridges the dpc.

•

Surface condensation caused by improvements to draught proofing of the building.

•

Above door and window openings where it is necessary to examine the type and condition of the lintels.

•

Interstitial condensation caused by moisture laden air passing from a dwelling to within the fabric of the structure and condensing on cooler surfaces.

•

Where there are signs of structural movement in the building and further investigation is required.

•

Increased risk of damp penetration caused by filling of cavities with insulation.

•

Guidance on this subject is available: BRE Good Building Guide 23 & 24.

•

Maintaining the robustness of the external and internal wall surfaces by the provision of adequate mechanical protection over insulation materials. e.g. externally applied insulation systems with render coat mechanical protection

•

Assessing external rendering for replacement or repair.

•

Repairing external rendering.

•

Avoidance of cold bridges around openings and when structural elements extend through thickness of the building envelope.

•

Where planning restrictions prevent the thermal upgrade of the building then International Construction Warranties may deem it appropriate to add an endorsement to the policy regarding the risk of condensation.

198

15.3

Protection of Render Renders are vulnerable to damage through exposure to extremes of temperature during the first few days. Therefore, the following appropriate precautions should be arranged in advance: •

In hot weather, the wall should be shaded from the direct heat of the sun or the work programmed to be carried out in the shade.

•

In cold weather, rendering should not be attempted when there is a risk of frost occurring during the day or the following night.

•

Air temperature should be at least 50C at the time of application.

•

When rendering has been applied, it should be prevented from drying out for two or three days until the mortar has hardened.

•

In drying winds, it may need to be kept damp by gentle spraying.

Where the condition and bond of the existing plaster can be shown to be adequate, it can remain with exception of the following: The existing plaster should be removed where: •

Where rising damp is present.

•

Where a chemical damp-proof course is installed.

•

At the junction of external walls and part walls to see if they are properly bonded.

•

Above openings to examine the makeup and condition of lintels.

•

Where there is possibility of bond timbers which may have decayed.

Where a chemically injected damp-proof course is installed it is necessary to remove the plaster one meter above the dpc level or 600mm above any apparent salt line/ dampness whichever is the higher.

199

Re-plastering work should be delayed as long as possible in order to encourage rapid evaporation of residual moisture and the building should be well ventilated during the drying period. Plastering work must comply with independent third-party certificates acceptable to International Construction Warranties Limited and the chemical damp-proof course manufacturers’ recommendations. Recommended plasters usually incorporate adhesives to increase resistance to the passage of hygroscopic salts from the wall into the plaster. They should not, however, act as a vapour barrier. Gypsum plaster should not be used in conjunction with chemically injected damp proof courses. The plaster should not bridge the damp-proof course or be in contact with the ground floor slab. Final redecoration should not be carried out until residual moisture has disappeared. Matt emulsion paint is recommended for the use during this period. Internally drilled holes which are concealed by skirting boards etc. should not be plugged. Other visible holes and external holes should be plugged.

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