Technical Bulletin Issue 11 by Sava

HI Technical Bulletin For registered members of the SAVA Certification Scheme

Issue 11 | November 2010 All content © National Energy Services, Ltd Welcome to Issue 11 of SAVA’s Home Inspector Technical Bulletin. The bulletin focuses on Home Condition Reports and associated non-energy issues. We trust that you will find the bulletin useful for your day-to-day work and we welcome any feedback you have about what you would like to see covered in future editions. The contents of this technical bulletin may supersede certain scheme rules or requirements appearing in the Product Rules, Inspection and Reporting Requirements, training manuals or elsewhere. Members must therefore ensure that they have read and understood this document. IN THIS ISSUE

Party Walls and loft extensions

Environmental damage claims

Reporting the presence of mining

Reader’s comment on conservatory article

Case study–1870 rural property

Penetrating damp

Party Walls and loft extensions

Ask the Expert–damp meter reading

Using party wall procedures, loft conversions invariably need the cooperation of neighbours. This is because

One of the most cost effective ways to

the work to convert the loft will interfere

enhance the value of your home and to

with the party wall.

increase the accommodation is a loft conversion. Loft conversions have been

Any alterations to the ceiling joists/new

a common form of extension for several

floors of the roof room that adjoins the

decades. In recent years, thanks to

party wall; the purlins supported in the party wall; the roof covering where it

more relaxed planning rules and difficulties in obtaining finance as a

co-operation and consent of neighbours

consequence of the current banking and since the middle of the nineteenth wider economic crisis, an extra room in century. The Party Wall Act 1996

abuts a party line; in fact, anything that relies on the party wall to provide support, might require notice to be

the roof has become the obvious

extended this requirement to the whole

served on adjoining neighbours in order

alternative to moving house.

of England and Wales from 1 July 1997.

to seek their co-operation.

In late 2008, planning law changes made This issue is covered in a previous HI Technical Bulletin, (January 2009, Issue it easier to convert a loft. For a

As Home Inspectors we are less likely to advise clients on proposals to convert

detached or semi-detached home you

6). We considered the impact of the

roof voids but we do need to be aware

no longer need permission for

Party Wall Act 1996 on the work of the

of the issues that might arise if

conversions that do not exceed 50 m3

Home Inspector, looking at the impact

inspecting a loft conversion when

and do not go within 20 cm of the eaves. on the need for party wall procedures on the cost of repairs and therefore the However, in inner London work on the party wall to a property has required the impact on condition ratings.

reporting on the condition of a dwelling.

(Continued on page 2) Page 1 of 12

HI Technical Bulletin Issue 11 | December 2010 | National Energy Services the adjoining property to be undermined. This could have led to disputes between neighbours  Or worse, the work could have

disturbed elements of the adjoining property, such as flashings and other roof coverings, roof structures or A party wall in a typical loft conversion. It will have been altered by the finish and support heating appliances (as in this case) but will also provide support to an altered roof structure (Continued from page 1)

even elements of the

Perhaps one of the most misunderstood

accommodation below in the

aspects of the Home Condition Report

neighbour property (e.g. cracks or

and the Home Condition Survey is how

loss of key in plaster)

to report the presence of mining in the

 Finally, the perceived loss of privacy

from being overlooked as a result of Having briefly outlined the law relating to such works, we shall look at the potential issues to be considered when assessing a loft conversion.

Reporting the presence of mining

area of the property. This article provides a brief summary of the importance of recording the presence of

the creation of a loft conversion

coal and salt mining activity (keeping in might also have caused relations with mind that there are other mining the neighbour to deteriorate activities too). This is why the Party Wall Act requires a

The first issue is to establish when the

The importance of this will become even

property owner to give notice to their

loft was converted. If the property is

more significant if proposals by the Coal

neighbour if they intend to carry out any

situated outside inner London, and it

Authority, intended to dovetail with the

work that might impact on the structural

was converted prior to 1 July 1997, the

replacement of their computer systems,

strength or support of the party wall, or

chances are that no formal procedures

are implemented in autumn 2011. The

cause damage to the neighbouring side

will have been entered into with

changes proposed are to:

of the wall. In doing so they can avoid

neighbours. However, in the case of loft

disputes and claims after work has

conversion works undertaken after this

begun.

 Stop providing access free of charge

to information relating to mining

date, the Home Inspector needs to

activity. This information might

advise in their report that legal enquiry

continue to be available through

be made to confirm that procedures

other sites who subscribe to obtain

were followed.

the Coal Authority data but this is not certain.

It is also important to alert legal advisers

 Limit the availability of information in

to the issue of whether any disputes remain as a consequence of these works.

the Mining Search Report relating to

Examples include:

subsidence claims in connection with coal mining made under the

 Neighbours who have previously

compensation scheme to the period

enjoyed a harmonious relationship

since 31 October 1994 (the practical

can easily be antagonised as a result

start date of the Authority). Searches

of noisy or messy and intrusive

currently provide information back as

building work.  The affect of noise, but more

View of neighbouring garden from loft window

far as 1984. The reasons behind these changes appear to relate to

importantly vibration, along the party wall could have caused elements of

(Continued on page 3)

Page 2 of 12

HI Technical Bulletin Issue 11 | December 2010 | National Energy Services

various online services that can provide basic checks of the risk of mining activity in the locality. However, the reliability of these is dependent upon whether the

(Continued from page 2)

the cost of storing the current information and other ‘cut backs’.

available online at www.coal.gov.uk/

information was sourced directly from

services/propertysearch/gazetteer/

the Coal Authority.

guidancenotesenglandwales.cfm

If you have any doubt about the

However, if a conveyancer is

in an area where mining activity has

possibility of mining activity in the inexperienced or fails to identify that the locality, it is best practice to recommend property is in an area of present or that a mining report is obtained.

previously taken place therefore will

previous mining activity then they can

According to the Coal Authority

become even more critical if the

potentially blame the HI if they also

guidance, there is a risk of coal or rock

proposals are adopted. Many think that

relied on ‘the advice on the ground’ and

salt mining and a CON 29M search

it is proximity to a mining shaft that is

the HI also failed to point out that the

(Mining search) is necessary in respect

relevant and fail to appreciate that

property is in a mining area.

of properties in certain specified places

Knowledge of whether a property is

in the counties and county boroughs of

located in a mining area is one of the

England & Wales listed in the box below.

Identifying in a survey that a property is

mining and the potential for mining subsidence can occur some considerable distance from a shaft head. The mine doesn’t just go down: it also goes in any direction over many metres out from the

HI’s tools of the trade. If you do not have specific local knowledge there are

shaft following the seam of coal, rock salt or other minerals being mined. In addition many old shafts are long since

In England

In Wales:

Bristol

Isle of Anglesey (Sir Ynys Môn)

capped but still a risk, while others are

Cheshire

Blaenau Gwent

not even known to the Coal Authority.

Cumbria

Bridgend (Pen-y-Bont Ar Ogwr)

Derbyshire

Caerphilly (Caerffili)

Devon (see guidance)

Carmarthenshire (Sir Gaerfyrddin)

Durham

Cardiff (Caerdydd)

East Riding of Yorkshire

Denbighshire (Sir Ddinbych)

identify many issues in their report that

Gloucestershire (including Forest of

Flintshire (Sir y Fflint)

the conveyancer might not otherwise be

Dean)

Merthyr Tydfil (Merthyr Tudful)

aware of. One of these might be that a

Greater Manchester

Monmouthshire (Sir Fynwy)

property is located in an area where

Herefordshire

Neath Port Talbot (Castell-Nedd Port

mining has taken place. Coal and brine

Kent

Talbot)

(rock salt) mining is usually identified

Lancashire

Newport (Casnewydd)

Leicestershire (but excluding Rutland)

Pembrokeshire (Sir Benfro)

Lincolnshire

Powys

Merseyside

Rhondda Cynon Taff

The Home Inspector is the ‘man (or woman) on the ground’ and is the ‘eyes and ears’ of the conveyancer. The HI will

through legal searches and conveyancers have codes of practice and guidance to assist them in making appropriate

Northumberland

(Rhondda Cynon Taf)

searches. This is documented in a joint

Nottinghamshire

Swansea (Abertawe)

publication produced by the Law Society

Shropshire

Torfaen (Tor-Faen)

and the Coal Authority, entitled

Somerset

Vale of Glamorgan (Bro Morgannwg)

“Coal Mining and Brine Subsidence

Staffordshire

Wrexham (Wrecsam)

Claim Searches: Directory and Guidance–

Tyne & Wear

6th edition”.

Warwickshire West Midlands

This is a useful reference tool from

Worcestershire

which the HI can learn more and is

Yorkshire (North, South, West)

Page 3 of 12

HI Technical Bulletin Issue 11 | December 2010 | National Energy Services

Case study–1870 rural property The following case study has been submitted by John Bennett. It relates to some of the key issues identified at a property previously associated with agricultural uses and highlights some of the issues of inspecting rural properties. The property is a large detached house built

Photo 1: Brick work under bay window

Photos 2 a & b: Spalling brickwork

around 1870 set in an area in excess of one acre. Local knowledge and information obtained from Local Authority maps confirmed that the property was originally a farm and that a new bypass had been constructed alongside its northern boundary. The property has solid brick walls under a pitched roof covered with natural slate with suspended and solid floors on the ground floor and timber upper floors. The property is generally in good order and has been maintained and decorated internally to a very high standard. The main issues with the property are summarised in this case study. D4. Main walls CR3 The external brickwork is cracked in a number of areas and some repairs are required. This has occurred at the point of

In some areas the external ground level is too high which has partly blocked an air vent to the suspended timber floor (Photo 3 over the page). This is considered serious and in need of urgent repair or replacement. Repairs and treatment to prevent further damage would be costly. Applying the condition rating path: J – Repairs are required, i.e. cracks filled, re-pointing and repair to damaged brickwork, lowering external ground level, damp proof course treatment L – Repairs: not cosmetic/minor–the performance of this element is impaired (condition of external solid wall may be allowing damp penetration) N – Defects do not currently affect the structural integrity but do spoil the intended function and would be very costly to repair P – This path delivers a CR3 (Continued on page 5)

weaknesses below the bay windows (Photo 1) and above the main entrance. Sloping floors in the dining room and on the first floor landing and distorted door frames provide further evidence of historic movement. After careful consideration of all the evidence, I concluded that the movement was not structurally serious or ongoing, although I stated in my report that minor seasonal movement may still occur. The more flexible original lime-based mortar joints have been re-pointed in places with strong cement mortar which hinders and restricts the evaporation of moisture from the bricks. This encourages water to dry out on the inner face of the wall and may therefore be a contributory factor to the damp found inside the property. The trapped moisture in the bricks may also freeze and this has damaged the faces of some bricks (Photo 2 a & b). There does not appear to be a damp proof course and high

A note on movement Movement is often found in and around bay windows to older properties. This is because where foundations to the building might be very shallow, the foundations to the bay were often even less substantial. As a consequence differential movement is commonly observed in this part of the structure. This kind of differential movement can also be more pronounced when the house is close to trees. In these circumstances it can be an early indicator that the main walls themselves might be undermined in the future if action is not taken to control the influence of the trees. Sometimes movement between the bay and the main structure is so serious that it indicates that the bay might actually need rebuilding or underpinning with a foundation design that is more appropriate and in balance with the main structure. This can be more obvious and necessary particularly with multi-storey bays.

Page 4 of 12

HI Technical Bulletin Issue 11 | December 2010 | National Energy Services (Continued from page 4)

E4. Floors (suspended timer) CR3 The timber floors to the ground floor and first floor are sloping in places. A house of this age does not have concrete foundations and some amount of historic movement may be expected and is not considered structurally significant. The internal decorations are in good order and there are no major cracks to the internal walls. The timber floor in the drawing room is very springy in the corner near to the fireplace. The external vents are partly blocked by the high ground level and there is a concern that damp has caused rot in the supporting floor joists. Further investigation is required to discover the actual cause and full extent of the problem and further advice should be obtained.

A note on mortar The use of cement mortar to re-point the brickwork of older housing stock is a commonly encountered problem in properties built before the second half of the twentieth century. Bricks manufactured up to this point were generally softer and as a consequence walls were less repellent to moisture. The walls would absorb a certain amount of moisture from the rain or air and the structure of the wall allowed it to ‘breath’. Moisture in the brickwork would be absorbed and then travel through the brickwork, attracted to the more absorbent lime mortar, before leaching back to the surface of the mortar joints. The lime mortar used to bed the bricks tended to be sacrificial, allowing the porous surfaces of the bricks to survive frost action and the mortar joint slowly degraded itself. By contrast the cement mortar repels moisture and hence the brick surface becomes more saturated, as it is the bricks only that absorb the moisture. In consequence frost action causes the bricks to spall, while the hard cement mortar remains intact.

Photo 3: Partly blocked vent

Applying the condition rating path: J – Repairs are required, i.e. the floor in the drawing room requires strengthening and floor joists may have to be replaced L – Repairs: not cosmetic/minor–the performance of this element is impaired N – Further investigation is required, i.e. floor boards will have to be lifted (to check for possible damp and woodworm) P – This path delivers a CR3 Environmental risks to the property The description of the service at the back of the HCS states: “The surveyor assumes that the home is not built with, nor contains hazardous material and is not built on contaminated land. If any materials are found during the inspection which may contain hazardous substances or if the surveyor finds evidence that the land may be contaminated, this will be reported and further investigation recommended.” In other words the HI has a duty to identify potential risks when there is evidence to be observed (see also the article Environmental damage claims on page 8). There was an old fuel pump in the grounds (Photo 4) that raised concerns for the presence of a redundant fuel tank below ground.

In worst cases penetrating dampness can be a bigger issue in older walls re-pointed with cement mortar and even the localised stability of the wall can be affected where the degradation of the brickwork is so extreme that bricks disintegrate.

The cost of decommissioning and decontamination can be considerable and I therefore recommended further investigation.

(Continued on page 6) Photo 4: Old fuel pump

Page 5 of 12

HI Technical Bulletin Issue 11 | December 2010 | National Energy Services (Continued from page 5)

The vendor stated that the tank had been decommissioned but could not produce the

Photo 6 : Acoustic fencing

paperwork. The standard text on contamination did not adequately explain the situation so the issue was also reported under Section C – “Legal issues and risks Photo 5: Transco gas installation

to property and people”. In addition a Transco gas installation (Photo 5) was found in a corner of the grounds. According to the vendor there was a leasing and access agreement regarding the installation and so a note was included under Section C–Issues for Legal Advisors. Re-instatement cost calculations and exceptional adjustments Finally, the 3 m high acoustic fencing (Photo 6) which was installed following the construction of the bypass was included at a value of £50,000 for insurance purposes following advice from the vendor. A quick search on the internet confirmed that this cost was not excessive.

A note on reinstatement costs Care should be taken when calculating reinstatement costs and the approach adopted by John is a good example of the additional adjustments that sometimes have to be made. The BCIS tables provide rebuilding cost figures based on model dwelling specifications and the additions such as walls, fencing and other items are also based on specific descriptions. Where the property you are inspecting varies significantly from the standard BCIS specification you need to make reasoned adjustments and make note of your assumptions in your site notes. If in doubt it might be necessary to recommend that specialist advice is obtained for the calculation of the reinstatement figure.

Environmental damage claims  Vegetation dieback, indicating

Early in 1992, as a consequence of claims we cannot see contamination or test for arising from environmental damage in

it as part of our inspections. However,

the US, insurers in the British market

we have a duty to identify potential risks

limited their exposure to environmental

of contamination when there is evidence

losses. Their alarm was aggravated by

to be observed during our inspections.

uncertainties concerning allocation of ultimate responsibility for the remediation of contaminated land, the lack of environmental standards and the possibility of further legislative proposals from the European Commission. As a result, professional insurance policy wordings were amended to exclude liability for losses arising from pollution or contamination. In surveys we therefore exclude reporting on contamination in, on, or under the ground in standard reports as

possible contamination  Sources of electro-magnetic radiation

on site or nearby such as telecom masts, electrical substations or

Evidence might include the less common features such as the fuel pump illustrated in the case study on the previous pages, but could also include:  Old oil storage tanks for heating

systems  Old cesspits (as opposed to septic

tanks) that might discharge onto

power lines This is not an exhaustive list! Surveyors and HIs also need to use publicly available information and local knowledge to identify previous uses of land which might include conversions of buildings and associated grounds from uses such as:

adjoining land and then into water courses  Invasive flora, such as Japanese

 Contaminative industrial uses such as

tanneries, dye works, engineering etc.

Knotweed & Giant Hogweed

Page 6 of 12

HI Technical Bulletin Issue 11 | December 2010 | National Energy Services (Continued from page 6)

 Agricultural contamination such as incineration

Japanese Knotweed

areas, slurry pits, animal burial.  In all commercial or agricultural conversions

the risk of the use of contaminative materials such as asbestos that may or may not have been stripped out upon conversion or used in

Giant Hogweed

ancillary buildings that have been demolished and cleared from the site  Landfill, mining and associated waste tipping

Desktop reviews can also indicate that potential contamination is present: the reader can be alerted to make further enquiry through careful

Do you agree with the Inspector? We like to hear your views. Have you come across a property that would make for an interesting case study? Contact the Editor with your views, opinions and ideas

warnings in Section C of the HCR or HCS.

Reader’s comment on conservatory article Following our article Assessing Conservatories featured in Issue 10 of the HI Technical Bulletin, Mike Sampier, Cheviot Surveys Ltd, wrote to the editor, commenting:

at: bulletins@nesltd.co.uk Indeed we have a duty of care and whilst Attention is drawn in the article to the we may not claim to be security experts

condition and adequacy of the

it would be remiss of us not to point out

separating door–but only in the context

obvious security weaknesses to our

of heat loss. The security of this door is

clients.

also important, particularly if it has been

The conservatory is a good example of a

removed!

situation where security may be very weak, particularly if the structure was

I have just read with interest the article

not erected to the appropriate BR

on conservatories published in the latest

standards. More so if a lean-to

HI Technical Bulletin. I did so in the

greenhouse has been adapted for use as

context of having recently renewed my

a living space (Photo 1), even if only for

home insurance policy, and having

seasonal occupation. For example,

undertaken a couple of insurance

louvered glass windows provided for

surveys where conservatories had

ventilation which typically have flimsy

suffered storm damage. In addition,

locks and glass panes that can be lifted

I have a long standing concern over the

out.

lack of any reference to security in the

Photo 2: Conservatory with door removed

A more general aspect of conservatory construction and use is the matter of heat gain. A south facing conservatory will regularly become intolerably hot in

original HCR and the present SAVA HCS.

summer unless there is mechanical

Whilst I appreciate that the regulatory

ventilation and effective sun shades

framework for the HCR precluded any

(preferably external).

mention of security in a survey that was essentially a ‘public’ document, there is no obvious reason why this aspect of a

(Continued on page 8)

property condition should be ignored in the HCS.

Photo 1: Greenhouse adapted to living space

Page 7 of 12

HI Technical Bulletin Issue 11 | December 2010 | National Energy Services (Continued from page 7)

Response from the Editor Mike raises a very interesting and valid

Lean-to conservatories are often

issue. The HCS was developed in a

constructed across existing windows,

format which very closely relates to the

and have an impact on the ventilation

HCR to give qualified Home Inspectors a

provision for the inner room. If that

competitive product to offer to

room is a kitchen where gas appliances

purchasers who require a report on the

are used then there may be a serious

condition of their intended purchase.

safety issue. Similarly condensation problems may be exacerbated by the reduced ventilation. I mentioned having recently renewed my home insurance. In the process of completing the data for the online comparison website I encountered the

However, the term ‘survey’ does imply something more than a report on condition and although the terms of engagement are well defined we are currently looking at several areas for improvement to the existing HCS product.

Penetrating damp Dampness can occur when water penetrates the fabric of the building, normally through roofs or walls. The cause of the penetration can be due to a defective material, poor building work or incorrect design. A surveyor needs to be familiar with these causes in order to follow the trail of evidence found during a building inspection. This article looks at some matters the surveyor should consider. Roofs Penetrating damp through roofs is usually caused by leaks due to the failure or incorrect installation of the covering material. Common materials are slate and tile to pitched roofs, lead, asphalt or bituminous felt to flat roofs.

basic security checklist that is now

The SAVA Condition Rating Protocol has

All roof cladding materials have a life

included in all insurance applications,

been revised and will be issued as

expectancy period and within this a ‘life

and it occurred to me that this would be

version 4 soon as part of these

to first maintenance’ period. When the

a valuable addition to the HCS. The

improvements.

covering material fails, it allows water

SAVA are also considering aspects such

ingress into buildings.

as reporting on security as potential

Locating the exact point of the leak in a

areas for improvement.

roof can be difficult, as penetrating

items include:  Key operated deadlocks on exit

doors (Photo 3)

water may travel along roof members

 Multi-point locks on sliding patio

and develop as a leak inside the

doors (Photo 4)

building some distance from the

 Key operated locks on windows

external defect. Water will follow the

(Photo 5)

path of least resistance and will often

 Padlocks on outbuildings (Photo 6)

penetrate a ceiling around light fittings. A common location for water penetration into a roof is at the junctions between it and the walls and chimneys (Photo 1 over the page). The junction is often made water tight Photo 5: Multi-point deadlock

with lead flashings, soakers, backgutters and front aprons. The flashings are usually lead, however zinc, copper and felt have also been used.

Photo 3: Key operated deadlock

Photo 4: Key operated window lock

(Continued on page 9) Photo 6: Padlock on outbuilding

Page 8 of 12

HI Technical Bulletin Issue 12 | xx 2010 | National Energy Services

Absorbed rainwater usually evaporates before reaching the inner face. Penetrating damp problems will usually occur in walls of this thickness and

Photo 1: Evidence of water penetration around chimney breast (Continued from page 8)

Comprehensive technical information

greater if the wall is in a severely exposed

can be found on the Lead Sheet

position, has defective rainwater goods or

Association website at

has a leaking overflow pipe or other

www.leadsheetassociation.org.uk.

plumbing leak.

Walls Penetrating damp is most commonly

Solid walls of 225 mm (one brick) thick

associated with the absorption of

and a render coat is usually required.

rainwater through solid walls. Rainwater

Penetrating damp also occurs in cavity

runs down the face of the wall or sits on

walls and is one of the most common

the top of parapet walls and soaks into

defects reported to the NHBC under their

the wall.

10 year guarantee on new houses.

Sand cement fillets were used in pre-

Most building materials have some

1920s houses and are a common cause

degree of permeability, bricks have

of water ingress. Sand cement is a rigid

varying degrees of permeability, class 'A'

material and suffers from initial

engineering bricks have the greatest

shrinkage resulting in cracking which

resistance to water absorption due to

allows water penetration, particularly

their dense pressed manufacture.

on the windward side of a building.

Common and facing bricks have varying

In general, lead flashings are more

degrees of permeability.

reliable. They should not exceed 1.8 m

Natural stone also has varying degrees of

in length and joints should be designed

permeability, limestone will readily soak

to prevent water ingress and resist

up ground and rain water whilst granite

wind uplift whilst allowing thermal

and marbles are water resistant. Using

movement. Joints can be welded,

low permeability materials create its own

lapped or hollow and solid roll. Lead

problems; the material does not absorb

flashings are secured to the vertical

rainwater and it streams down the face of

face with lead or copper clips or

the wall and is absorbed by the porous

wedges to prevent wind uplift.

mortar bed joints. Having accumulated

The spacing of the clips should be determined by wind exposure, in severely exposed locations the flashing may require a continuous clip. When lead is used as a flat roof covering it is the area of the lead which is a critical factor because it has a high coefficient of thermal expansion. A lining of building paper should be used

over the wall area the rainwater increases near to ground level and can produce

invariably suffer from penetrating damp

A cavity is built into a wall to prevent water penetration by creating a gap between the inner and outer leafs. However, problems arise when the cavity is bridged. Bridging of a cavity results when an obstruction passes across the cavity, such as wall ties, overflow pipes, insulation, window and door jambs and lintels. Cavity wall ties are manufactured with a drip or twist in the tie which should prevent water travelling across the tie. However, during construction mortar ‘snots’ are often dropped down the cavity and sit on the wall tie bridging the cavity. Partial cavity insulation bats are often installed using the wrong ties and this also allows bridging.

similar symptoms to rising damp (diagram bottom right).

(Continued on page 10)

Render coats were often used to increase water resistance on solid walls, their purpose being to create a water resistant face to prevent water absorption into the solid porous facing bricks or block-work.

between the lead and roof deck to

In moderately exposed positions most

accommodate the thermal movement

325 mm thick solid brick walls will resist

and prevent excessive erosion of the

water penetration.

Page 9 of 12

HI Technical Bulletin Issue 12 | xx 2010 | National Energy Services

Brick cuts, wall ties and other debris are often found at the bottom of cavities and these cause penetrating damp at DPC level, often mistaken for rising damp.

(Continued from page 9)

Oil based moisture sealants are prone to cracking as the oils dry and their life span

Cleaning the cavities at DPC level can cure suspected rising damp in some situations.

Polyurethane foam cavity insulation

can be as short as one year. Polysulphide

injected into cavities was also a common cause of bridging around wall ties as the

sealants are an improvement on oil based Damp-proof courses should be installed sealants and can have a life expectancy of under coping stones on parapet walls to

foam prevented the tie drip or twist from

over 15 years and have better adhesive

prevent the downward ingress of water,

functioning.

properties and slump qualities.

and lead flashings should be carried down

It is common practice for new properties

When applied correctly, silicon sealants

to have the cavity of a wall filled with rigid with primers and backing beads have a insulation during construction and if not life span in excess of 25 years and exceed carefully and properly installed can lead

the adhesion, movement and slump

to water penetration across the joints of

performance of the previous sealants.

from the copings to tie in with lead flashings and soakers on the roof. Coping stones should have a drip chased into the underside of the overhang and this should be kept free of the mortar bedding

the insulation. The BRE publication

material. The drip is often bridged by the

Thermal insulation: avoiding the risks

joint mortar which should be 'jointed' to

provides guidance on which method of

form a continuous drip along the length

external wall construction and insulation

of the wall.

is appropriate for specific levels of

Simple good working practice would

exposure.

prevent many water penetration

Water penetration is common around

problems and good maintenance.

door and window frames (Photo 2) where the frames have not been adequately

Attending to leaking gutters and Photo 3: Application of poysulphide sealant

plumbing leaks before they cause penetrating damp would also drastically

sealed. All frames should have a

Penetrating damp in door and window

continuous sealant applied to the

reveals can occur in both solid and cavity

perimeter of the frame against the

walls. In solid walls the windows are

external face of the wall (Photo 3). Careful consideration should be given to

usually set within the front 200 mm of the HIGGINS ASSOCIATES, 1995, edited by wall and this allows for water ingress into Stephen Neale, November 2010

the selection of the sealant.

the reveals on exposed elevations or

reduce the number of penetrating damp problems.

where a porous building material has been used. In cavity walls penetrating damp of the window or door reveals is usually due to the absence of the vertical DPC in the jamb where the brickwork is returned to form a solid wall to close the cavity. Vertical DPCs were introduced in the 1965 Building Regulations and houses Photo 2: Localised damp patch near door and window frame

built prior to 1965 with cavity wall construction may not have a vertical DPC (Photo 4). Current regulations are

Photo 4: Vertical dpc

insistent upon insulated jambs and proprietary cavity jamb closers incorporating a vertical DPC. Click on a headline to read other articles in this bulletin | Party Walls | Reporting the presence of mining | Case Study–1870 rural property | Environmental claims | Reader’s comment-conservatories | Penetrating damp | Ask the Expert–damp meter readings |

Page 10 of 12

HI Technical Bulletin Issue 11 | December 2010 | National Energy Services

Ask the Expert– damp meter reading “I have just read the latest HI Technical Bulletin Issue 10 and have a couple of queries regarding the best practice for damp meter readings. Firstly, as best

'G', 'Y' or 'R' (or use black/blue/red colour-coded dots) to confirm exactly where readings were taken and what level of dampness they indicated–would this be a satisfactory approach offering adequate protection in the event of a

Taking moisture meter readings around a door opening, using the capacitance or scan function

complaint or claim?”

practice, would sketches in elevation as

readings at one metre intervals and,

well as in floor-plan 'from above' not be

Russell Lock, DipHI MRPSA

required? When training as an HI, I

other areas of potential risk, this was not

seem to remember being advised to

Response from the Editor Russell describes his own practice of

provide such sketches so that the height

recording moisture meter readings and

judgement.

at which readings were taken can be

this appears to be a good example of

noted in order to evidence whether

best practice. However, he also asks for

rising or penetrating damp applies.

clarification on two clear questions:

The floor plan sketch was used more to

although readings should be taken in considered in the Fryer v Bunney

Surveying practice has undergone continual improvement since that time, particularly in the recording of what we

Would elevation sketches where

see on site. Therefore my conclusion

simply identify where readings had been

the position of damp meter

was that best practice is to at least

taken rather than the results of those

readings are recorded around door

annotate where no dampness was found

readings, and to highlight any

and window openings be best

and to record on a sketch (elevation or

obstructions to those readings being

practice?

otherwise) the position of readings

taken such as furniture.

This is essentially the same question I

Secondly, is more detail regarding the

posed myself in the article in Issue 10 of

readings themselves not required? The

the HI Bulletin. It is fair to say that my

best practice outlined seems to simply

recommendation to annotate in the site

indicate whether damp is present or not. notes the fact that readings have been Whereas a bit more detail could be taken around such openings is based on useful, especially when recording rising damp. For example: readings taken just above skirting boards can be high and become progressively lower the higher up the wall the readings are taken. In training I was encouraged to quote on

current case law. It is also the case that case law has not tested this point since Fryer v Bunney in the 1980s. At that time is was

taken where dampness had been discovered. However, I am aware of practitioners who are already undertaking the next stage in the development of best practice and are recording damp meter readings at all positions taken on elevation sketches (see diagram on page 12) in the way that Russell describes. 2.

readings themselves not required?

understood that the surveyor’s best practice was to take damp meter

Is more detail regarding the

Firstly, although it might provide

the elevation plan the actual meter

additional detail to the practitioner, it is

readings; whilst this may be going too

not necessary to record the actual

far it may be useful to quote as green/

readings taken unless you are carrying

yellow/red or low/medium/high.

out a meaningful empirical analysis of

My own proposed method of recording

the levels of dampness in the wall or

damp meter readings is therefore to use

other feature of the building. Moisture

a floor plan sketch to confirm where

meters are calibrated to take readings in

readings were taken and any

cellulose-based materials (usually timber

obstructions present such as furniture, and then on elevation sketches quote

Taking moisture meter readings in timber skirting board, using the resistance function, inserting the pins into the timber

in buildings). (Continued on page 12)

Page 11 of 12

HI Technical Bulletin Issue 11 | December 2010 | National Energy Services We can hypothesise as to the sources

(Continued from page 11)

and causes of the various forms of The readings (percentage or otherwise)

dampness based on these readings and

recorded by the moisture meter in other

the other evidence we see on site such

materials such as brick, plaster or mortar

as lack of sub-floor ventilation, high

are only relative and cannot be relied on

external ground levels or poor pointing.

as an accurate indication of moisture

However, accurate diagnosis can in

levels.

many cases require invasive investigation (taking readings deep in

Secondly, we use the resistance and capacitance functions of moisture meters to help us to initially assess whether

in checking for evidence of the approximate moisture content in walls etc. If we identify the presence of relatively high moisture content by use of the moisture meter then we should be looking for other evidence to suggest the possible causes. It is therefore sufficient to record in site notes either that low or high levels of moisture are present at the approximate position where the reading has been taken.

the wall, use of the hygroscope and taking material samples for analysis).

dampness is present in walls and

In other words the moisture meter

associated elements of a structure when

used in the context of the work we do

undertaking Home Condition Surveys, or

as Home Inspectors should never be

even more detailed Building Surveys.

seen as a test but as a tool to assist us

An illustration of how one of our HI Candidates has chosen to record the positions where he has taken moisture meter readings on the internal surface of elevational walls (with thanks to John Hathaway-Collins).

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