SA Roofing May 2016 | Issue: 79

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MAY 2016 ISSUE: 79

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MAY 2016

ISSUE: 79

EDITOR’S COMMENTS...................................................................................................... 2 CONTRIBUTORS & EVENTS........................................................................................... 4 COVER STORY............................................................................................................... 6-10 ROOF STRUCTURE FAILURES................................................................................ 13-14 LIGHT GAUGE STEEL TRUSSES...............................................................................17-18 WATERPROOFING..................................................................................................... 19-20 OVER-ROOFING ASBESTOS................................................................................... 23-26 PAINTS & COATINGS................................................................................................ 28-31 THATCH......................................................................................................................... 32-36 BULK INSULATION.......................................................................................................... 39

Trademax Publications SA Roofing Tel: 0861 SA ROOF (0861 727 663) Fax: 0866 991 346 Email: info@trademax.co.za www.trademax.co.za Postnet Suite 241 Private Bag X103 N1 City 7463

ROOF TILE MACHINERY................................................................................................ 40 PUBLISHER: Billy Perrin 082 266 6976 billy@trademax.co.za EDITOR: Celéste Perrin editor@trademax.co.za ADVERTISING: Jacqui Marsh jacqui@trademax.co.za LAYOUT & DESIGN: Craig Patterson craig@trademax.co.za SUBSCRIPTIONS: Belinda Thwesha belinda@trademax.co.za DISCLAIMER The views expressed herein are not necessarily those of Trademax Publications. Although we have done our best to ensure the accuracy of our content, neither Trademax Publications nor SA Roofing magazine will be held liable for any views expressed or information disseminated, in editorial content or advertisements, in this issue.

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EDITOR’S COMMENTS

With flying colours Events of the past week or so have given me pause to consider a world without colour. Frankly, in such a place everything would be off-colour.

T

he reason for my sentimentality over colour has nothing at all to do with roofing. A few days ago, the revered musician known as Prince, author of the timeless song and album titled Purple Rain, died. You don’t have to be old-ish, like me, to appreciate what an exceptional talent he was, or what an icon. Purple Rain has been playing repeatedly on most radio stations – all over the world – and hence my thoughts have been drifting. When I Googled ‘purple,’ almost the entire search result came up with…yes, you’ve already guessed it. So let’s move on to a horse of another colour. Or not.

While we may not be completely in the dark, I strongly doubt that many (if any) of us notice to what extent our daily lives are infused by colour. And I’m not talking about colour only in its literal sense. I’m talking about important matters, like dealing with red tape (I think of all the building and safety regulations that have to be adhered to, albeit for good reason), getting rid of a white elephant in the workplace, or scoring brownie points with the boss. Things are not always black and white, that much I’ve learnt.

This edition of SA Roofing features an in-depth article by SAPMA, the paint experts. I am very pleased to be sharing their expert insight on roofing restoration and coatings.

These are important facets that are sometimes not given enough attention. I am also happy about the article because my husband is colour-blind. (Oh, I’m not worried about possibly embarrassing him…he just denies it and, besides, he has no problem telling everyone that his wife can talk a blue streak.) This is a golden opportunity for me to imprint on him the importance of consulting professionals when it comes to matters of importance – like paint selection.

In this issue you will not find any red herrings, no grey areas, and no black magic. I must stop smiling though, because while I may be tickled pink at my playful indulgence in colourful words, SA Roofing is in fact a serious trade publication. In a time of doom and gloom though, perhaps I will be pardoned for this atypical lighter take on things.

I leave you with the assurance that, from our LCP Roofing cover story all the way through to the last page, you might just find that silver bullet in answer to your roofing question.

I hope you enjoy the read. And, as always, you have carte blanche to send me any questions or other feedback.

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CONTRIBUTORS & EVENTS

Contributors LYNDSAY COTTON Lyndsay Cotton began his career in the construction industry in 1989 as a Technical Assistant at the City Council of Pretoria. He graduated in 1992 with a BSc (QS) degree and obtained a Diploma in Project Management shortly thereafter. Cotton has been directly involved in the construction of well over 300 projects, including upmarket complexes and ultra-luxury individual residential units.

He is the current Chairman of and serving on the Board of Directors for the ITC-SA (the Institute for Timber Construction SA), which is the only professional body representing timber construction in South Africa. Well versed in residential construction particularly, Cotton is renowned for his knowledge of and expertise in all aspects of roofs and roofing. He is particularly passionate about maintaining high levels of professionalism in the industry, as is evidenced by his regular contributions towards continued education of all stakeholders involved in the roofing business. Cotton has authored several instructive commentaries and articles on important roofing matters, many of which have been published in the SA Roofing magazine and elsewhere, or been disseminated via the ITC-SA network. He readily shares information that is aligned with his commitment to uphold the highest standards in roofing.

He was part of the team that established LCP Roofing (Pty) Ltd. in 2010 and currently serves as General Manager. The company now boasts, amongst other achievements, the SANS1900 accreditation for monoplaner prefabricated timber roof trusses (nail plated).

SA Roofing welcomes the SA Paint Manufacturing Association (SAPMA) to this issue and thanks the association for its editorial contribution that highlights some very important aspects of roof restoration, and painting specifically.

TINUS DE JAGER Tinus de Jager completed his roof inspector’s training in 2000 through Roof Inspection Services, which was headed up by the late Victor Booth, a Specialist Engineer in Timber Engineering. Under Mr Booth’s mentorship, de Jager gained expert knowledge and experience in conducting both domestic and commercial roof structure inspections. De Jager became an accredited ITC-SA member (the Institute for Timber Construction SA) in 2001 and has served on the ITC-SA Board of Directors as Inspector Director.

Other duties for the ITC-SA have included qualifying audits on licensed truss fabricators prior to issuing such fabricators with a ‘Certificate of Competence.’ In 2005, de Jager successfully completed the ITC-SA Basic Estimator Designer course.

He also founded Dynamic Roofs, a truss manufacturing plant offering design, manufacturing and erection services for new roof structures, which he oversaw from 2009 to 2011. With a wealth of experience under his belt, de Jager regularly does roof structure assessments for private home owners, insurance companies, banks and engineering firms.

DION MARSH Dion Marsh holds a National Diploma in Quantity Surveying and Construction Management. Involved in the roofing industry for close to 25 years already, his extensive experience ranges from contracting to manufacture and supply. More specifically, he has served as a member of the SAMCRA Technical Committee (the Southern African Metal Cladding and Roofing Association) and also as a member of the SANS1273 Working Group.

As the General Manager of Ash & Lacy South Africa (Pty) Ltd, a division of Ash & Lacy Building Systems UK, Marsh oversees the operation’s manufacture and supply of innovative and cost-effective building envelope solutions that yield ongoing savings throughout the entire operational life of the building. He works closely with design professionals, property developers, contractors and building owners, offering expert consultation on energy-efficient roofing and cladding solutions that focus on sustainability and the reduction of carbon emissions.

Highly skilled in conducting comprehensive roof and cladding refurbishment assessments – including alternative asbestos abatement methods – Marsh is also a noted authority on the groundbreaking Ashgrid spacer system, having played an instrumental role in launching and establishing the system. With his in-depth knowledge of the South African roofing and cladding sectors, Marsh remains committed to providing the industry with premium products, forward-thinking solutions and unmatched customer service.

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COV E R S TO RY

Failing to prepare is preparing to fail A successful roofing project will enjoy optimal ‘flow’ on site. This is also critical for the contractor, fabricator and erector, as each party strives to fulfil his responsibilities and move on to the next task at hand. In this article, Lyndsay Cotton shares insight into problems and solutions for improved site preparation and better collaboration among the different contractors – practical information that can help a roofing project flow without unnecessary complications.

Article by: Lyndsay Cotton, General Manager of LCP Roofing and Chairman of the ITC-SA

T

he ultimate goal of the professional roofer is to successfully close out the roofing phase of a building project on time and within budget. Accurate scheduling and effective site communication go a long way towards achieving this goal, especially when there is good cooperation between the roofing contractor and the main contractor or project manager.

resources and skills to meet project deliverables. Instead, they concentrate on their expertise in managing external professionals and particular skills as required and suited to specific projects.

Nowadays, forward-thinking building professionals and project managers are differentiating themselves from competitors by focusing on how they deliver their expertise, rather than on what they offer. This new approach is in line with the life cycles of modern construction projects, which are seeing a noticeable shift towards project management-based processes.

There is a definite trend growing in South Africa that not only roofing professionals but the construction industry as a whole should take cognizance of: Projects (mainly residential) are being given to the amateur building professional to not only start, but to complete, despite the work so often being fraught with problems, delays and substandard workmanship. This is partly due to rising building costs, but more noticeably because information and resources are so readily available to the unproven owner-builder or part-time project manager.

Due to the almost infinite variety of project types commonly undertaken by individual construction companies, building professionals can no longer rely on extensive in-house

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PROBLEM TREND IN SA

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COV E R S TO RY

PROBLEMS: BUILDING DESIGN Due to an unremitting demand for more cost-effective designs, the designs of buildings themselves are often inadequate or incorrect. Fewer and fewer architectural professionals are getting involved in residential building design, and drawings are often flawed or issued with very little or no supporting information or documentation. Some of the most common problems are: • No roof layout drawings on plans: • This is problematic because the design of the roof layout is not up to the roofing contractor; the design responsibility of the building, including the roof arrangement, lies with the architectural professional.

• The roofing professional will place the roof, designed according to a rational design, on the building according to the aesthetic requirements of the architect or client.

• Incorrectly designed roof layouts: • Mono roofs abutting into or above windows, openings or doors.

• Instances where roofs fall into and against upper level walls.

• Where rainwater discharges over entrances and doorways.

• Placement of chimneys in valleys and two valleys converging into one. The negative effect of this cannot be overemphasized.

• Overlay hips under 500mm are very problematic on tiled roofs; and, where the pitch is less than 17.5 degrees, overlays should be even up to 1m wider.

• Gable overhangs that, due to their width, cannot support either their own weight or that of the roof covering.

• Incorrect specification or total omission of vital information (whether a design requirement or a local authority requirement): • Roof pitch.

• Roof loadings (what the roof will be loaded with). For example: Air-conditioning units or ducting, geysers or solar panels, and electrical ducting.

• Types of ceilings required. (Suspended or nailed-up ceilings call for different bracing requirements.)

• Types of roof covering/Roof covering specifications.

(Some types of coverings cannot be laid below a minimum roof pitch.)

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• Overhang required. (This can have a significant impact on the roof loading and costs.)

• Internal bearing walls not indicated.

• Dimensions either not noted, or the building does not square out.

• Sections and elevations. (Especially where special trusses or ceiling details are required.)

• Incorrect or poor material specifications: • Examples include timber sizes no longer manufactured, timber grades no longer available, trade/brand names either not available or not applicable, and inefficient specifications or not keeping in touch with modern design methods.

• Where ‘copy & paste’ roof notes do not match the actual descriptions on the drawings and/or specifications.

• Roof coverings not suited to the terrain categories.

• Addition of ‘lean-to’ roofs that are not compatible with the minimum specifications of the roof coverings. Also, inadequate support for lean-to roofs.

• Insufficient head heights and lintol depths, especially on patios.

• Specifications in contravention of the National Building Regulations. (For example, the specification of a roof wire holding-down detail on a metal sheeted roof.)

• Specification of non-rigid ceiling and insulation materials, which interfere with the bracing details of a roof structure. (That is, the application of expanded polystyrene foam (EPS) insulation products in-between the rafters and the battens or purlins without adequate consideration for the bracing rules.)

• Purlin spacing on metal sheeted roofs which do not cater for, or contravene, the terrain category where the roof will be erected.

• The ‘kink’ on a Bali or Polynesian roof specified in the incorrect position.

Although the abovementioned points are very important and warrant attention, it is not commonplace for the roofing professional to be involved or consulted during the design stage, and so he can become heir to several of these problems.

However, many of these points can usually be addressed in the early stages of the project and the pertinent and relevant complications can be resolved.

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COV E R S TO RY PROBLEMS: BUILDING CONSTRUCTION • Roof bearing problems are significant. Roofs work on the principles of squares, 45-degree diagonals and triangles of various configurations, heights and pitches.

• Skew walls; the foundation is wrong. This refers to the ability of building contractors and their bricklayers to set buildings out accurately. Whilst many building elements can accommodate such setting-out errors (internal walls can be ‘packed’ out, or floor tiles can be laid diagonally), it is at the point when the roof is measured up that it becomes apparent that the building is ‘out-of-square.’

• Walls that taper vertically either inwards or outwards.

• Inadequate bearing surfaces. It is good practice to build the final brickwork layer as a header course.

• Slabs and upstand beams. Where roof trusses, concrete roof slabs and upstand beams are coincidently part of the roof structure of a building, certain rules must be followed.

• A truss wall plate cannot be on the same level as the top of the concrete on a roof slab, as the roof truss overhang and slab waterproofing have to be catered for. This is even more significant where abutting upstand beams have to be catered for.

• Roof slabs must be constructed before the roof trusses are required to be erected.

• Parapets and gables: In order to prepare the adjoining vertical surfaces before the trusses are installed, specific care must be taken in the plastering and/or finishing of the brickwork. The building contractor should be able to determine all finished levels from either the architect’s drawings or his own expertise.

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• Parapet walls not built to the correct height. This is especially problematic where a roof structure comprises of beams and rafters, as surfaces can be installed at the incorrect pitch.

• Gables not built to the correct height or pitch.

• Wall corbels.

• Corbels are not shown on the plans but built, or corbels are built to sizes far exceeding the maximum allowed by SANS10400.

• Omission of header courses where corbels cut into the overhangs.

• Inadequate knowledge of the National Building Regulations.

• Insufficient lintol depths over openings.

• Absent, non-structural or non-conforming support to roofing components.

• Incorrect holding-down details for different roof types.

• Deviations from approved plans, standard details and layouts.

• Unauthorized and non-documented changes.

• Omission of structural elements.

• Changes of building sizes and layouts.

• Addition of, or changes to, chimneys not originally allowed for in the design phase.

• Failure to resubmit change documentation to the local authorities.

• Failure to produce updated and accurate drawings with correct drawing numbers and, most importantly, revision numbers, dates and submission to the relevant subcontractors.

• Sites not ready for roof installation.

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HEARTY CONGRATULATIONS FROM SA ROOFING!

ROOF STRUCTURE FINAL DESIGN, FABRICATION AND ERECTION STAGE There is a significant amount of work and planning that goes into the final roof design, fabrication and erection stage.

Problems encountered on the previous stages are further exacerbated by: • Buildings not being ready to be measured for final design on the agreed-to dates. This could result in: • Delayed production schedules.

• Potential price increases.

• Reallocation of logistic and human resources to other projects.

• Unavailability of roofing materials.

• Access limitations: • Delays due to access control limitations of personnel.

• Physical access restrictions of delivery vehicles to sites.

Roof trusses can be up to 13m long (and even longer). A tile delivery vehicle can have a gross vehicle mass of up to 55 tons.

• Lack of or inadequate lay-down areas for timber trusses and roof tiles.

• Restrictions in working hours.

• Restrictions due to environmental considerations.

• Restrictions due to the main contractor not complying with local authority or estate regulations.

• Building work not complete: • Lintols not built or brickwork mortar still ‘green.’

• Formwork to upstand beams not stripped.

• Roof wires or hoop iron straps not installed, or incorrectly built in.

• Gable or dividing walls not built.

• Internal load bearing walls not built.

• Beam filling not done before the commencement of roof coverings.

• Plastering not done where overhead work is still to be executed. (The side or gable wall for a double storey section over a single storey garage.)

• Slabs not cast and upstand brickwork on slabs not built.

• Chimneys not built.

• Walls are not built level, not only on one gridline, but across the entire building.

• Plaster sand and cement not on site before tiling work commences.

• Last brick courses not laid as a header course or not jointed properly.

• Entrance piers or arches over porte cochère not complete.

• Main contractor deliverables not on site: • Client supply items such as sand and cement for ridging not available.

• Special boarding or insulation not delivered on time.

• Client-supplied services for finishings, such as sanding or painting before erection, not arranged timeously.

• Agreed-to contractual arrangements not met.

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SOLUTIONS AND CHECKLISTS

COV E R S TO RY

5 MAY 2016 MARKS LCP ROOFING’S 6TH BIRTHDAY.

If these issues are identified prior to commencement of the project, the roofing professional, through detailed interaction with his client, can take several pre-emptive steps to prevent and resolve a number of serious problems that would otherwise occur.

A checklist for the main contractor and fabricator will assist in ensuring that the roofing portion of the construction project is started and completed without delays.

A: THE MAIN CONTRACTOR »»The final-approved construction drawings are followed without deviation; »»The fabricator is a professional member of the Institute for Timber Construction SA (ITC-SA) with a current certificate of competence; »»The fabricator designer is professionally registered and qualified to design for the fabrication of the roof according to the categories of, and as defined by, the ITC-SA; »»The quotation received is in accordance with the minimum requirements as laid down by the ITC-SA; »»SANS10400-XA National Energy Regulations are complied with; »»The roofing professional is supplied with the correct drawings and revisions; »»The roofing professional has supplied a roofing solution according to the accepted quotation; »»The roofing professional is informed of the site measure date in a timely manner; »»The main contractor is fully conversant with the National Building Regulations and they are being strictly complied with, namely: »» Lintols are constructed according to regulations under SANS10400-K Annex B »» Holding-down details are correctly installed and according to the correctly designed truss spacings and roof coverings quoted for - as per SANS10400-K 4.2.11 Roof fixing, SANS10400-K 4.3 and 4.4 »» Corbel projections do not exceed the 1/3 rule unless a rational design is done, and the corbels are clearly indicated on the drawings »» Minimum pitches are designed for as per SANS10400-L and the manufacturer’s minimum specifications »» Geyser supports are discussed and provided for as per SANS10400-L »»The final brick course is built as a header course unless aesthetic requirements dictate otherwise; »»Site access is arranged. Permits and access control is approved; »»A level and suitable lay-down area is provided for delivery of the roofing materials; »»Solar panels and/or solar geysers that are required or provided for in the specifications are indeed designed for; »»All roof slabs are constructed and upstand beams or brickwork is in place; »»All bearing surfaces are designed to support the roof structure; »»Main contractor deliverables are in place; »»Main contractor-supplied scaffold and hoisting facilities are in place; »»All health and safety requirements are communicated to the erector; and »»A competent foreman is in attendance at all times.

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COV E R S TO RY B: THE FABRICATOR »»The main contractor is fully conversant with the terms and conditions of the quotation; »»Latest date for site measurements and deliverable dates are agreed upon; »»Site is ready for measure before visiting the site; »»The client file is up to date, with specific notes of the following on file: »» The accepted and signed quotation »» The accepted and signed roof layout »» The specific terms and conditions of the contract are ratified »» Special trusses and technical drawings are approved »»The roof structure and related elements are designed according to best practice and to the minimum requirements of the relevant building regulations, any statutory regulating authority such as the NHBRC, and the representative professional body – the ITC-SA; »»The fabricator holds himself accountable for designing to the minimum prescribed standards of his membership of the ITC-SA (the only representative professional body in the fields of roofs and roofing in South Africa); »»A complete and detailed erection drawing will be supplied on site; »»It is agreed not to accept substandard building practices, especially relative to the placement of a roof structure on the bearing surfaces; »»Where practical, the main contractor will be warned of any inability by the fabricator to perform, due to nonperformance of others or otherwise, and practical advice will be offered. It must be clearly noted that it is not the duty of the fabricator to design elements of the building structure save for the roof structure itself. This responsibility, without doubt, rests with the architect and structural engineer.

KNOWLEDGE OF CONSTRUCTION DETAILS It is important that the main contractor be a practicing expert on all construction details related to the site management of the roofing trade. He is not expected to be a roofing structure design or layout specialist, but he must understand and be completely conversant with the components that make up a roof structure. As such, he must understand the relationship between the various elements.

The main contractor is the vital link that connects all the building trades. He must control the sequence of trades and make sound decisions about the role of the fabricator and erector on site.

The advice, information and examples contained in this article are intended to be of benefit to not only main contractors, fabricators and roofing erectors, but all those with an interest in the construction and erection of roof structures, with the aim of furthering discussion around real problems and practical solutions that will better enable roofing projects to come to successful completion.

FOR MORE INFORMATION, CONTACT: LCP Roofing (Pty) Ltd. Lyndsay Cotton (c) 082 564 2730 | 0861 LCPROOF (e) lyndsay@lcproofing.co.za (w) www.lcproofing.co.za

C: THE ERECTOR »»Is a professional member of the ITC-SA. »»Will erect the roof structure in full compliance with the erection drawings, minimum standards as prescribed by the National Building Regulations, and according to the bracing rules as laid down by the ITC-SA.

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ROO F S TRU C T U R E FA I LU R E S

On dangerous ground The serious problem of roof structure failures, and the concern around the frequency with which they occur, received much-needed attention in the previous edition of SA Roofing. It is no coincidence that, here, we address another disastrous collapse.

Information provided by: Tinus de Jager, Certified Inspector (SAQA); ITC-COC/0125/INS

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ast month, while SA Roofing was talking to certified roof inspector Tinus de Jager about his article on roof structure failures (that appeared in the April edition), he informed us that he had just received an urgent call to investigate yet another structural roof failure.

The roof failure, which had been discovered by the building tenants, occurred in perfect weather just after employees had started leaving for their homes that afternoon. The owner, understandably very worried as this happened at the start of a long weekend, contacted the ITC-SA (the Institute for Timber Construction SA) for the names and numbers of engineers or inspectors who might be available to assist. Eventually the contractor was able to reach de Jager, who was glad to help.

ACTION TAKEN As a start, the immediate area was cordoned off with barrier tape, and the building was rendered completely off limits to all employees.

Once on site, de Jager was accompanied by the main contractor and a safety officer and given a brief safety induction. They proceeded to enter the first floor where the collapse had occurred, to do an inspection of the area.

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They needed to determine the condition of the remaining roof sections on both sides of the collapse in order to make recommendations on which steps to take, to ensure that the sections were made safe enough to allow for further clearingup activities. It was safe enough for the tenant to remove sensitive documents, furniture, computers and personal belongings that had not been completely damaged or destroyed, from the building. It was agreed that de Jager would do a further assessment of the remaining roof structure the following day.

Subsequent to his second inspection, de Jager concluded that the entire remaining roof structure was unsafe for continued use. Steel-covered scaffolding walkways were then constructed throughout all the passageways on the first floor, to enable people to come in and remove all their remaining valuables.

FINDINGS In explaining why this collapse occurred, de Jager says it is not a clear-cut case. “I would hesitate to claim what the primary cause for failure was, but from experience I am quite certain that it was a combination of bad practice, ineffective remedial work, and the possibility of manufacturing errors,” he says, adding, “The latter, however, can only be confirmed once, or if ever, the original design documentation can be obtained.”

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ROO F S TRU C T U R E FA I LU R E S There were also numerous examples of non-compliance with standard roof erecting procedures. De Jager concluded that previous remedial work was ineffective and inconsistent and probably aggravated the situation in some instances.

A combination of all the above factors just made it impossible for the structure to perform, ultimately resulting in the failure.

NEXT STEPS De Jager recommended that the building be evacuated as soon as possible and that the current roof structure be removed to allow for the construction of a new roof structure. This was by no means an easy recommendation, he states. “I must make it clear that a decision like this is not made lightly, as the cost implications are enormous. People’s safety, however, remains the overruling priority in such findings.”

A tender process will now be initiated for the supply and installation of a new roof structure. Special attention will be given to ensure that the contractor responsible for the erection of the new roof is capable and qualified for the job.

Quotations for the supply of the trusses will be carefully scrutinized to ensure that all design requirements in terms of additional loads as well as bracing materials and sundries have been taken into account.

The final designs will also have to be checked by the respective systems engineers. This is a standard procedure followed with regard to all systems for public buildings.

PREVENTION Could this collapse have been prevented? “The first thought that came to my mind was that a thorough visual inspection should have been done just after the erection of the structure,” de Jager says. “Many of the inadequacies could and would have been noticed then and could have been addressed or rectified immediately.”

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An annual structural inspection, as is now required by law, should have taken place a year after the initial construction. De Jager feels certain that such an assessment would surely have picked up the first signs of failure, or at least have revealed non-compliances in terms of the basic Roof Erecting Procedures.

ROLE OF THE INSPECTOR De Jager feels strongly that inspectors must get more involved, and he references Regulation no. 8 under the new Construction Regulations, which makes provision for the appointment of a Competent Person by the Principal Contractor to oversee a particular section of a project, where the size and risk profile of the project necessitates the supervision of such construction.

“Roof inspectors should not be shy to offer their services to clients, especially the owners of commercial buildings, to ensure that roofs are being erected correctly. This service will ensure that correct procedures are being followed during the erection phase and that poor habits and incorrect practices are eliminated.”

De Jager says that, in his experience, owners are willing to pay for such a service. “For this purpose, I am in the process of drafting a guideline to assist erectors in following a sequence of effective roof erecting procedures that will eliminate the bad practices that have caused so many failures to date.”

“I have no doubt that, if proper supervision takes place during the erection process to ensure compliance with general good practice, we will make great strides in eliminating roof failures in the future,” he concludes.

For more information, the author can be reached via e-mail to: Tinusdj@hotmail.com.

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A network of more than 190 licensed roof truss manufacturers across South Africa, provides a competitive and economic solution to even the most complex of roofing problems. This MiTek fabricator network, using MiTek’s state-of-the-art software programs, provides high quality, purposeengineered truss units to satisfy the need of an ever increasing complex roof market. The scope of MiTek’s services includes not only unrivalled expertise in terms of professional structural engineering service but also the extensive Research and Development into all aspects of timber and light gauge steel roof design and construction as well as a full range of manufacturing equipment - that makes MiTek a World Leader. creating the advantage World Leaders since 1956.

MiTek Park,754 16th Road, Randjespark, Ext. 34, Halfway House,1685. Midrand (Head Office) Tel: + 27(0) 11 237 8700 Cape Town Tel: 021 905 0244 • Durban Tel: 031 700 6332 • Port Elizabeth Tel: 041 581 7525 email: marketing@mitek.co.za • www.mii.com/southafrica *MiTek

Industries South Africa (Pty)Ltd, a division of the worldwide MiTek Group.

Ultra-Span the best choice for this roof

L I G HT G AU G E S TE E L TRU S S E S

®

When it came to the roof design of the Siyabuswa Community Hall, it was evident that an optimal solution was going to be required due to its large span. But the obvious choice was immediately clear.

Roof erection: Multiples of four trusses were framed together on the ground before being lifted onto the building with a crane.

W

hen Bapedi Consulting Engineers asked Giant Engineering for a roof structure estimate for the Siyabuswa Community Hall, a primary consideration for Edward Curry from Giant Engineering was the large span involved. Knowing that it offers a span of 20,5m, Curry had no hesitation in choosing Ultra-Span ® Light Gauge Steel (LGS) for the roof structure design of this important public facility. The quote was accepted without any problems.

This is a relatively large roof structure at more than 1,000m² with clear spanning trusses of 20,5m. And yet it only required 8,500kg of Ultra-Span ® LGS, which represents a mass of 8,4kg/m² for the complete roof structure.

Giant Engineering, a long-standing MiTek-licensed truss supplier, proceeded to install not only the roof structure, but also the roof sheeting, the Dutch hip-end louvres, as well as all the gutters.

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Completed roof: A team of six people constructed the complete roof structure in just five days.

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L I G HT G AU G E S TE E L TRU S S E S

Large span 20,5m internal view: At just over 1,000m² this roof structure, with clear spanning trusses of 20,5m, only required 8,500kg of Ultra-Span® LGS. This works out to a mass of 8,4kg/m².

QUICK WORK

Uwe Schlüter, Business Development Manager at MiTek, says many of the other MiTek-licensed timber truss suppliers are, just like Giant Engineering, also starting to provide Ultra-Span ® LGS roof structures as it enables them to cater for a much larger section of the market with great success.

The trusses were all pre-assembled in the factory, with the large trusses done in two halves for site splicing. Multiples of four trusses were first framed together on the ground before finally being lifted by crane onto the building.

On site, Giant Engineering had to retrofit special MiTek tiedown straps to the inside of the walls, as no original tie-down straps had been fitted by the contractor. Despite this, the full roof structure erection was completed in just five days with a team of six people.

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MiTek South Africa (t) +27 011 237 8700 (e) marketing@mitek.co.za (w) www.mitek.co.za

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FOR MORE INFORMATION:

Turn the wheel for the right product to meet your project requirements Tel: 011 462 9122 ati@ati-insulations.co.za www.alububble.co.za

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WATE R PROO F I N G

Exclusive rooftop garden calls for innovative waterproofing Waterfall Equestrian Estate, situated on a hilltop in Midrand, houses some of Johannesburg’s most luxurious homes on beautifully landscaped grounds.

It was here that Kaytech supplied an innovative drainage system that would effectively maintain the integrity of a rooftop garden.

I

n addition to magnificent homes, the estate boasts stables, paddocks and an equestrian arena that add to its sustainable and integrated ecology. In keeping with this environment, Rekopane Landscapers suggested the creation of a rooftop garden as a special feature on one of the homes.

FOUR COMPONENTS When approached by the landscapers for assistance in the vitally important drainage of the rooftop garden, Kaytech’s Winnie van der Merwe suggested a fourcomponent system consisting of a layer of bidim A4, a layer of Flownet, a third layer of Kaytape, and a final layer of bidim A2.

Bidim A4 protects the waterproofing layer.

Rekopane Landscapers started off by installing waterproofing directly onto the roof. For protection of this waterproofing, bidim A4 was installed. Bidim is Kaytech’s multi-graded continuous filament, non-woven, needlepunched geotextile – manufactured from 100% recycled polyester. The needlepunching process provides several advantages, including an appreciable thickness, high porosity, and a high drainage capacity. When incorporated in a subsoil drain, bidim allows the highest possible throughflow rate while still providing excellent filtration characteristics.

To control the flowpath of water, Flownet DN3, a heavyduty, extruded, HDPE drainage net with directional flow was installed over the bidim A4. Used as a drainage core, Flownet replaces the need for stone aggregate in subsoil and structural drains. A layer of Kaytape S270 was subsequently rolled out over the Flownet. This slit film, woven polypropylene tape geotextile acts as a high modulus separator that, in this application, would keep open the flowpaths and prevent the low modulus bidim from intruding into the Flownet openings.

Kaytape S120 is laid over the Flownet.

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The composite drain was completed with the installation of a top filter layer of bidim A2. In total, 100m2 of each product was used for the drainage of the roof garden.

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WATE R PROO F I N G

To add filtration diameter to the drainage system and to help prevent clogging of the bidim, a layer of high-quality, clean river sand (minimum 50mm thick) was placed over the drainage system and covered with a final layer of topsoil.

Rekopane Landscapers was highly impressed with the ease and speed of installation of these products that enabled them to complete the entire project within one day.

The final bidim A2 layer separates the cover soil from the woven tape underneath.

The trusty hard hat – still hard at work The constant movement of heavy equipment and tools can pose a very real danger to anyone located on an industrial or construction site. Serious head injuries can be avoided by using a rugged but comfortable hard hat.

T

he Beluga hard hat by North has undergone all mandatory requirements in accordance with the standard set out by the SABS, says Stephan Poole, Supply Chain Manager for North. “It has been tested for electrical insulation, resistance to penetration and flames, shock absorption and chin strap anchorage strength.”

The Beluga is manufactured locally in accordance with stringent SANS1397:2003 requirements.

What other aspects make for a quality hard hat?

The Beluga: • Is manufactured from either polypropylene (PP) or acrylonitrile butadiene styrene (ABS) raw material.

• Is able to withstand impact of up to 5kN according to the SABS standard.

• Has vents for air circulation to ensure that the wearer stays cooler.

• Comes with either plastic or steel lamp brackets.

• Is available with recessed earmuff slots.

• Has a sun brim visor that offers sun protection on the neck, while a peak offers good protection from the elements.

• Has a water ‘gutter’ that assists with water run-off when working in the rain.

• Provides a choice: The standard click-lock and a ratchet assembly, or a foam or leatherette headband.

The four-point chin straps can also be fitted with or without a chin cup.

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The Beluga hard hat.

The Beluga has stayed with the times, offering definitive lines in a wide range of colours for a more modern look in addition to comfort and safety. “It comes complete with 30mm accessory slots, a four-point nylon web suspension with a forehead comfort band, and a crown pad. It is ideally-suited to workers in all industries where head protection is required,” Poole concludes.

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Reg No: CoR18.3 2013/068719/07

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MANUFACTURERS OF

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SUPPLIERS OF HIGH QUALITY, TESTED DAMP-PROOFING AND WATERPROOFING PRODUCTS • Chemical dpc creams • APP Bitumen Membranes • UV Protective Coatings • Long-lasting water repellents Provision of training & advice Approved Applicators Johannesburg: 011 708 3603 Cape Town: 021 982 5131 Strand: 021 854 4506 Email: info@safeguardchem.co.za

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OV E R- ROO F I N G A S B E S TOS

Health and safety guidelines when overroofing an asbestos cement roof

Due to problems in old asbestos cement roofs and lately also with fibre cement profiled roofs and their roof lights, it has become commonplace to ‘over sheet’ the existing roofs with a spacer system and new profiled metal sheets. There are several key reasons for this, as Dion Marsh explains.

Article by: Dion Marsh, General Manager of Ash & Lacy South Africa (Pty) Ltd.

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irst, the expensive and hazardous process of a roof removal and disposal is avoided, and environmental damage averted. Then, there is the opportunity for additional insulation to be installed, ensuring compliance with energy efficiency regulations. Another important consideration is that operations within the building can continue without disruption. Additionally, the enclosure of the asbestos cement roof sheets prevents any further risk of weathering or deterioration, rendering the material inert and safe for the remainder of the life cycle of the building.

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TAKE NOTE It has been established through consultation with industry colleagues that, as with most roofing activities, there are different views on how tasks should be carried out for particular situations.

For many reasons, the over-roofing of existing, fragile roofing materials is no exception. As with most guidance documents, we cannot be prescriptive. It is therefore essential that all companies embarking on this type of work make themselves aware of the hazards likely to be encountered – and that they implement the control measures necessary to reduce those risks to the minimum possible.

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OV E R- ROO F I N G A S B E S TOS

ASHGRID METHOD The Ashgrid bar and bracket spacer system is secured through the troughs of the existing asbestos cement roof sheets into the underlying purlin. The drilling process is carried out in conjunction with an H-series asbestos-certified vacuum cleaner, which captures 100% of the dust produced. Insulating the resultant cavity is highly recommended, and with certain building occupancy classes it is mandatory in order to comply with SANS10400-XA. A suitable outer weather sheet is then installed to the new Ashgrid bars, using conventional fixing methods.

PLANNING A comprehensive evaluation of the existing roof and its location must first be undertaken to establish its suitability for over-roofing. Factors to be considered include: • Condition of asbestos cement sheets (friable or damaged), roof lights and glazing.

• Suitability of roof and gutters to accept the selected system.

• Adequacy of existing structure to accept additional load of selected system.

• Internal access for installation of safety and debris nets.

• External access for installation of scaffolding, loading platforms and edge protection.

• Presence of overhead, high-power electricity cables.

• Suitability of access and ground conditions for a crane or other means of hoisting materials to roof level.

SAFETY MEASURES Before work commences, a comprehensive risk assessment must be carried out to identify the specific hazards faced and any counteractive control measures required to ensure the health and safety of both roof workers as well as others in the vicinity who may not be directly involved but might be affected. Examples include: • Prevention of exposure to asbestos fibres in the unlikely event they are released during the fixing of spacer system brackets through the roof sheet.

• Prevention of falls through fragile roof surfaces – for people, equipment and replacement materials.

• Prevention of persons falling from roof edges or into the building.

• Prevention of debris (arising from work) falling from roof edges or into the building.

• Hoisting and distribution of materials to, along, and over the roof.

• Means of rescuing persons as a result of falls, into nets or suspension from harnesses.

• Measures to protect others below or in the vicinity of the work being done.

• Verifying the experience, qualifications and training of the operatives in order to ensure their ability to carry out the work efficiently and safely.

• Ensuring that materials to be installed are classified nonfragile.

NOTE: This is not an exhaustive list; the onus remains on the contractor to ensure that all possible precautions to minimize risk are considered and properly implemented as required.

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OV E R- ROO F I N G A S B E S TOS

Prior to roofing materials being loaded directly onto the roof structure, the adequacy of the roof to accept the additional loads must be verified as acceptable by a qualified structural engineer.

All hoisting arrangements must be subject to prior planning, initiated and supervised by a competent person.

SAFE SYSTEMS OF WORK It is essential that a method statement/safe working system be devised in consultation with the client/building occupant. This must take into account the abovementioned factors and that only appropriately supervised, trained, qualified and experienced operatives should be used for the work.

The preferred option to prevent injury from falls is safety nets, which are established as an effective form of fall protection.

They should preferably be installed internally, close to the underside of the existing roof, to provide collective protection.

Due consideration must be given to ensuring sufficient clearance over racking and other equipment to allow for the deflection of the safety net when arresting a person’s fall.

It should be noted that safety nets will not relieve the contractor from his duty to minimize the risk of falls through the existing fragile roof during the over-roofing work. Crawling boards or similar types of safety equipment must also be in place and used when operatives need to traverse the existing fragile roof.

Where it is not practical or possible to install nets internally, alternative steps must be taken to prevent falls through the existing fragile roof material. These can include the use of sacrificial safety nets that are left in position over the existing roof and below the new sheets. However, due consideration must be given to the additional risks the net installers will encounter before deciding to use this system, as well as the controls necessary when working on fragile roofs to install these nets. If used, these must be adequately secured around the perimeter of the roof and to each other. It should be noted that this option is generally only suitable for profiled sheets used with a bracket and bar, or a top fixed bar over cladding system.

ROOF ACCESS & EGRESS It is vital that a safe means of access and egress is established for the roof work. The most effective means of providing a safe working environment and ease of access around a fragile roof is a fully boarded perimeter scaffold, positioned no more than 300mm below eaves level, that includes additional lifts at gable ends.

The preferred method of access and egress to and from the scaffold platform is via a purpose-fitted staircase. This scaffold should provide perimeter edge protection and ideally also means of manoeuvring materials into position and fixing the initial row of 1-metre long spacers from the gable and the first tier of sheets without accessing the roof. The scaffold should incorporate purpose-designed loading bays for mechanicallyhoisted roof sheets and materials. These should be strategically positioned to reduce as much as possible the unnecessary manual handling of new roof materials at roof level.

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Safety nets for all applications must be installed by trained and competent installers in a manner that does not pose additional risks to the installer or building occupants.

Another option is the use of lightweight timber crawling boards – a minimum of 600mm wide – positioned strategically and spanning at least three purlins at the leading edge, and utilizing the new roof as a working platform. Where practical and possible, a system that incorporates means of attaching safety harnesses should be utilized when working from crawling boards without the safety nets. If not utilized, sufficient crawling boards must be used to safely manoeuvre enough of them in turn to ensure continuity of fall protection for the whole leading edge. Some longer crawling boards are manufactured to provide harness securing points. However, their size can make them heavy and difficult to move over a profiled sheet safely, and this can create an additional hazard.

Short, lightweight boards spanning no more than three purlins are easier to move and will always provide a platform from which to move the one adjacent to it as work progresses, if utilized correctly.

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RESCUE PLAN The decision to implement any process will be governed by a number of site-based factors and the need to provide the optimum protection for those working on roofs or doing below-roof work.

Where fall arrest systems such as nets and harnesses rather than fall prevention methods are utilized, it warrants a reminder that a specific rescue plan must be established in accordance with the Occupational Health & Safety Regulations.

DEBRIS AND DUST FROM INSTALLATION To provide adequate fixing positions for spacer systems that will support the new roof, holes will be drilled through the existing asbestos/fibre cement profiled sheet. It is essential that steps are taken to prevent the dust emanating from this process from releasing fibres into the building or atmosphere.

The preferred option is the use of an H-series vacuum cleaner.

All drilling is carried out in conjunction with this specialized vacuum, which is designed to capture any dust and asbestos fibres created during the drilling process. The powerful H-series vacuum cleaner is fitted with an Ulpa Filter for 99.999% efficiency at 0.12 micron. It is ESD safe, meets HSG264 standards of surveying, and is fully compliant with BS EN 60335-2-69. An Internet video clip can be viewed here: https:// youtu.be/QNemGnOf_kQ.

The use of self-drilling or tapping screws to form the holes provides an opportunity to apply a light grease or similar substance to the screws before use. Alternatively, a coating of wallpaper paste or similar substance may be applied to the

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original roof along the spacer fixing line. The substance used will collect dust emanating from the drilling process, aided by the spiral thread on the screws, and will prevent it from being released into the atmosphere when the holes are drilled.

Any debris created through accidental breakage must be treated as hazardous waste, be thoroughly damped down and placed in sealed bags for disposal at a licensed site.

PERSONAL PROTECTION It is unlikely that asbestos fibres of any significant quantity will be released into the air during this type of work. However, as part of the project’s risk assessment, extra precautions to protect the people carrying out the work must be considered and implemented as needed. Examples are the use of disposable overalls and FFP3 filter masks appropriate for the wearer.

IMPORTANT NOTES The advisory measures contained in this article are not exhaustive; they are intended to provide information and advice on methods that can be adopted or adapted to ensure that the work is carried out as safely as possible. Roofing contractors are free to select any method that is safe to use, supported by a robust risk assessment, and compliant with all current legislation.

Within the South African regulations, there is no requirement to be registered as an approved asbestos contractor to carry out asbestos roof enclosures. It is, however, still a requirement that an employer or self-employed person notify the Provincial Director of the Department of Labour in writing prior to the commencement of asbestos work, and to ensure that written procedures are laid down and followed to prevent the release of asbestos dust into the environment. All suitable Health and Occupational Safety precautions should be followed whilst carrying out the work.

All asbestos work carried out in South Africa should be in accordance with Government Gazette Regulation No. 7276 Vol. 440, Pretoria, 10 February 2002, No. 23108.

For more information, the author can be reached via e-mail to: Dion.Marsh@ashandlacy.com.

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Roofing Matters:

What you should know about roof restoration (Part 1) Roofing professionals know what an important part of one’s home the roof is. It makes up about 40% of the external surface and acts as the first line of defence against the elements. In this, the first of two articles in our regular Roofing Matters series, expert Toni Stella tells us why roof restoration is so important – and how to get it right.

Article by: Toni Stella, National Training Manager of the SA Paint Manufacturing Association (SAPMA)

Check the condition of your roof thoroughly and carry out any necessary repairs before painting it, SAPMA advises.

R

estoration is the upgrade and rejuvenation of an existing roof, and includes several aspects. Restoration work can be undertaken on various roof types, but the most commonly restored roofs in South Africa are metal roofs and those with concrete tiles.

Full restoration work normally extends to: • Cleaning and removal of lichen • Repairs, including re-pointing, re-mortaring and/or reflashing • Replacement of damaged tiles or roof sheeting • Application of a coating system

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A quick distinction between roof repairs and roof coating (painting) is warranted: If roof repairs –such as leaks– are not fixed, they can become expensive problems and potentially even dangerous, e.g. when water comes into contact with electrical wiring or fittings. Restoring and applying a colour coating system will extend the life of the roof and improve its aesthetic appeal, but repainting by itself will not solve all repair or restoration problems. More specifically, repainting alone is not the solution to roofs that are leaking, have become extremely porous, have faulty laps or cracked tiles, are rusting, or where the mortar has deteriorated. If the roof is very old and has considerable erosion or surface weathering, those areas of the roof will most likely need to be replaced as they will be unsuitable and unsatisfactory to recoat.

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PA I NT S & COATI N G S

Using a high-pressure water blaster is one of the best ways to clean a roof, especially a roof with a rough surface.

TO RESTORE OR NOT If it is determined that a roof is suitable to be restored, it is a very worthwhile option as, depending on the age of the roof, this could further extend its life by as much as 15-20 years, in addition to giving it a new appearance.

In some instances roof restoration is not an option, including when the roof is pitted or eroded, and particularly once it has become extremely porous (absorbing water) through age.

Another example is metal roofing with severe rust that will require significant and costly repairs to make the roof watertight. If the repair is in fact even possible, the cost involved will prove uneconomical. In cases like these, full roof replacement is advisable.

ABC’S OF RESTORATION Typically, if the roof’s general condition and/or surface coating has deteriorated with age and needs upgrading, it’s time for some restoration work.

There are a number of reasons for painting roofs, with the two main objectives being improved appearance and protection.

Similarly, when you repaint a roof, the goal is usually to recolour it and restore the overall finished appearance, resulting in a new-looking, attractive roof.

Appearance: The surface of every roof will deteriorate over time, and may eventually look dull and faded. Visible rust, fungi and stains will worsen the problem and make the roof appear blotchy and messy. Roofs in this condition will seriously detract from the overall appearance, appeal and value of a house. Alternatively, a roof may be in good condition but the owner may wish to change its colour to give the house some fresh new appeal. In either case, painting the roof is decorative, enhancing the appearance of the house and adding to its value.

Protection: After years of exposure to the elements (rain, wind, hail, sunlight), every roof will experience a degree of decay.

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Rust may be destroying the sheets on galvanized roofs, leading to leaks that need repair. Cementitious surfaces will degrade due to weather and chemical exposure. These surfaces may then become porous, absorbing rainwater and placing a huge amount of stress on the roof trusses. In both instances, painting is a protective function that helps prevent the need for costly repairs while safeguarding the homeowner’s investment.

CONSIDER THIS BEFORE PAINTING A ROOF • What sort of roof is this? Most roofs comprise of either galvanized iron or concrete tile, but because there will be significant differences in the age and condition of the roof, this can change the system SAPMA recommends. And, the question must be asked: Is the roof already painted?

• Is it corrugated or IBR? • Is it a clay or slate tile?

• Is it a Chromadek ® roof?

• How old is the roof?

• What is the condition of the roof and paint system?

• Roofs in good condition are easy to paint.

• NOTE: Old and uncoated metal roofs may look sound, but will have a vastly reduced layer of zinc left and may need a second coat of primer.

• Tile roofs may be contaminated with mould.

• Is the home (or building) close to the sea – say within 500 metres?

• Roofs close to the sea should have two coats of primer applied.

• The underside of exposed galvanized soffits must have extra coats of primer.

• Roughly how big is the roof?

• To determine correct paint quantities and select the most appropriate accessories, you need to know if it’s concrete tile or corrugated or IBR. • Are you painting the roof yourself? If so, you will need information on: 1. How to correctly and safely prepare the roof for painting.

2. How to correctly and safely apply the paint.

3. The correct paint system.

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TERMINOLOGY AND TECHNICAL TERMS IN ROOF PAINTING RIDGE CAPPING:

The special tiles that run along the top of the roof set in mortar.

HIP CAPPING:

Similar to ridge capping, but the special tiles run along any sloping functions at the tops of the roof tiles, also set in mortar.

VALLEY:

The intersection of two sloping roof surfaces, towards which water flows (the opposite of a hip).

EAVES:

The area underneath the lowest, overhanging part of the roof.

FASCIA:

The eaves gutter is normally fixed to a metal or timber fascia, which runs along the bottom edge of the roof.

FLASHING:

A strip of material (usually metal) that covers the area between the roof tiles and another surface such as a pipe, chimney, roof light or a wall.

SKILLION:

A roof that slopes in one direction only, frequently covering an addition to the home. It often has a shallower pitch slope than the main roof.

SARKING:

A layer of boarding and/or a layer of waterproofing material fixed underneath the roof tiles. Waterproofing sarking is frequently needed under skillion roofs.

ROOF MATERIALS: TILES AND METAL • Cement-based roof tiles:

The texture and colour of the tiles affect the preparation and painting.

• Granular or stone chip tiles: These tiles look and feel rough. This is due to the coating of small granular stone chips that is added by slurry to the surface of the tile after manufacture. This layer of stone chips tends to loosen, often quite quickly due to abrasion and the effects of heavy rain and hail.

• Pigmented cement tiles: These tiles are recognized by the fact that the colour penetrates throughout the whole tile, i.e. it does not only coat the surface of the tile. This permeating pigment is achieved by adding oxide to the cement.

• Factory-applied coating of pigmented slurry: These tiles tend to be earthy colours. The colour is a thin layer on the surface only but does not actually penetrate the tile. Because the slurry-coated surface may degrade over time, it is important that it be checked thoroughly before painting.

• Fibre-reinforced cement roof tiles:

Fibre cement roof tiles are flatter and thinner than cementbased roof tiles. They are a natural dull grey colour. They are also available in a variety of profiled sheets, which may be easily painted.

• Clay roof tiles:

These tiles have a very smooth surface that looks like baked clay, and they have a yellow ochre colouring. Clay tiles should not be painted. Although clay tiles are porous to water, the paint particles are too large to penetrate and adhere to the tile.

• Slate roof tiles:

Slate roof tiles are most commonly a dark grey or black colour and usually have a very shiny appearance. It is not feasible to paint slate, as it is non-porous and paint does not adhere to the surface well. Therefore, slate roofs should never be painted – the paint will simply peel away from the surface.

• Harveytile lightweight steel sheeting: These are galvanized metal sheets that have a layer of grit applied to the surface, making the surface very durable so that it does not usually require painting.

• Chromadek ®: These metal sheets have a smooth baked-on colour coating applied at the factory. They are available in a variety of colours and do not usually require painting. If they are painted, careful preparation is necessary.

STEP-BY-STEP ROOF PAINTING Regardless of the material the roof is made of, all roofs must be cleaned before any paint is applied.

1 Cleaning the roof Roof cleaning depends on the budget and materials available.

Using a high-pressure water blaster is one of the best ways to clean a roof, especially roofs with a rough surface. You could also use a broom and hose, but will need a fungal wash to help remove the mould from within the pores of the surface. This is where high pressure is good: it gets into all those nooks and crannies. For roofs with a smooth surface like galvanized iron, high pressure is also good, but these roofs can be washed quite easily with a broom, some detergent, and a hose for rinsing afterwards.

2 (A) Painting a corrugated/IBR iron roof A new iron roof must be washed with a degreaser before paint work starts, unless the roof is more than one year old and has weathered. (This means that the oil from fabrication has worn away and the iron has been slightly etched through weathering.)

Unpainted galvanized iron, as well as any sheets of galvanized iron that may have been replaced on an existing roof, must first be primed with a suitable primer. Two coats of suitable paint will have to be applied. As for colour, this is a personal choice but it is worth noting that lighter colours will reflect the heat, whereas darker colours will absorb the heat.

• Metal roofs: • Galvanized corrugated iron and IBR sheeting: These roofs are recognized by their corrugated profiles and their metallic finish. If properly prepared, they can be very successfully painted.

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• You should spray about a metre-wide section and work your way down the sheet, spraying in the direction of the flutes in the corrugated iron. The joints in the iron can serve as a guide, making for an easy way to tell exactly where you are at. Once you have worked your way down the sheet and completed that section, move back to the top of the roof and repeat for the next sheet of corrugated iron.

You must keep a wet edge at all times – that is why you go back to the top of the roof before it starts to dry. If you decide to work back from the bottom to the top, the top part could have tacked off by the time you get back up there.

You can also buy rollers that are shaped like corrugated iron.

They do work well, but you will still need to cut in all the corners and ridge caps. With some roofs you may need to run the brush down the join in the sheets, because sometimes they are slightly raised and the roller will not get into this area.

You could also choose to brush paint the complete roof. (I have done it in the past, but that was before I bought my first airless spray gun.) If you decide to use a brush, there are a few things to remember:

If the roof looks really bad, and just about all the colour has gone, it will have to be sealed first. Most roof sealers or primers dry clear. It is important to apply this liberally and give the roof a good coating so that it can properly soak into the tile.

As with any roof, two coats of suitable paint must be applied.

Again, for choice of colour, remember that darker colours absorb the heat while light colours reflect the heat.

For a tiled roof, airless spraying is also the best and the quickest way to paint, and again there is a technique involved: • Paint about four tiles down from the top, and then paint across the roof until you get to the other end. From there, go back to where you started and repeat spraying about four tiles down again. Then continue across the roof to the other end. Each time you start a section, paint up to the bottom edge of the previous tile painted. This will help avoid overlap marks.

You could also choose to paint a tiled roof with a brush, but it will take a long time to complete the task. One suggestion is to hire an airless spray gun. The money spent on the rental will be made worthwhile by the time saved.

• Start early in the morning, and do not try to paint in the heat of the day – the paint will dry far too quickly. Another thing to remember is to work in small sections, similar to spraying, but maybe only a half-sheet width at a time. Also, make the overlap mark the hollow of the corrugated iron and not on the top of the ridge.

2 (B) Painting a tiled roof Typically, a tiled roof gets painted because all the existing slurry or coating has worn off and the roof is looking a bit shabby.

With tiled roofs, there is a common issue with ridge capping.

They may very well need to be fixed before painting can start.

This is generally referred to as ‘pointing and bedding of ridge caps.’ Most will need re-pointing and some many need rebedding.

With re-bedding, you take off the ridge cap and re-bed it in a new mix of mortar. Pointing is where the ridge cap is not moved but the outer mortar is repaired, generally with another layer of mortar applied over the existing layer. If any repairs like these were done after the roof was cleaned, it is important to use a (garden) hose and give the roof a final clean. Sometimes a broom can also do the trick.

PA I NT S & COATI N G S

Airless spraying is the quickest way to paint any roof, but it requires a certain technique in applying the paint:

THE RIGHT PAINTING CONTRACTOR

Painting a roof will not only improve its appearance, it will also add protection against the elements, says Toni Stella, SAPMA Training Manager.

Whether it’s for your home or an industrial or commercial building, using a skilled, professional painting contractor takes the stress out of painting. But finding the right one is an important decision that requires careful consideration. The SA Paint Manufacturing Association (SAPMA) has reputable paint contractors as members and is happy to supply their contact details and assist with other paint inquiries.

For more information, call SAPMA on 011 615 1195.

DO YOU HAVE A GREAT PROJECT OR STORY TO SHARE WITH SA ROOFING READERS? Send your article and high resolution images to editor@trademax.co.za or call 0861 727 663 for more information.

YOUR PRINT MEDIA PARTNER OF CHOICE, SUPPORTING LOCAL TRADE.

CONTACT US: info@trademax.co.za / 0861 727 663 / www.trademax.co.za

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Worthy of praise When the task fell to Biggarsberg Thatchers to build eight Zulu huts to be used for guest lodging at the historically important Ncome Zulu Cultural Museum, they made every effort to ensure that the results do the site justice. It’s clear that their objective was fully met.

Interior of a Nguqa sithandaze Zulu hut.

T

he Ncome Zulu Cultural Museum is built on the site of the legendary Battle of Blood River that took place in 1838. The museum overlooks the bronze wagons or ‘wagon laager’ of the Voortrekker (Boer) Commandos across from the Ncome River/Bloed Rivier (so named in isiZulu and Afrikaans respectively).

The focus of the Biggarsberg Thatchers brief was the construction of the Zulu huts, known as ‘Nguqa sithandaze.’

Nguqa means bend. The doors are traditionally very low, hence the need for bending. Sithandaze means prayer. The Nguqa sithandaze is traditionally used for the purposes of thanksgiving, prayer and worship ceremonies for the departed.

Today the cluster of eight thatched huts serves as accommodation for tourists visiting the former battlefield.

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NGUQA SITHANDAZE CHALLENGES AND SOLUTIONS The project presented a few challenges, which included the laying of the thatch grass and the binding of the grass to the laths. Due to the curvature of the domed-shaped structures, the grass tended to lift and separate from the bundles below.

But Biggarsberg Thatchers simply proceeded to select all the finer thatch grass from their warehouses, which then ensured a smooth and even finish to the exterior of the roofs.

Another factor was that the fibreglass centrepiece acts as a skylight, and this is the only natural light in the building. These fibreglass installations to the ridge were challenging as they were manufactured off-site and had to be modified on-site to suit each individual dome.

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The Zulu thatch huts at the Ncome Zulu Cultural Museum.

FUNCTIONAL EXTRA FEATURES Biggarsberg Thatchers added several enhancing features: The covering to the metal ring beams was achieved by the thatch grass being soaked in water to soften the fibres and then being plaited into ropes. (The traditional Zulu name for these ropes is ‘umjiko.’) The plaited ropes were then used to wrap the metal ring beams.

Thatch rolls were used as beam filling, which resulted in a natural and very aesthetically pleasing finish.

One rather comical challenge was to discourage the builders on the site from sleeping inside the huts. Thatch grass offers excellent thermal properties that keep the huts very cool in summer and very warm in winter, and they therefore quickly became the preferred place to sleep.

The thatching of the eight Nguqa sithandazes took the Biggarsberg Thatchers team approximately eight weeks to complete.

For more information, visit www.thatcher.co.za.

The thatched gatehouse at Ncome Zulu Cultural Museum.

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Thatch – all the insulation you need Thatch is by far the most natural product to use on a roof, as it is harvested off the land and used without going through processes to create an actual roof covering. With the high thermal values of thatch, there is no need for any other products to create insulation.

Source: TASA - Guide to Thatch Construction in South Africa

Photo credit: Shaun Dunmall

T

hatching in South Africa is a fast-growing industry. In an environment where more members of the public are leaning towards natural materials used in ‘green design’ and construction, and thatch being a completely natural roofing product, thatching is growing in popularity.

Looking at roofs from a ‘green’ point of view, the best roof one can put on a building would be a thatch roof. First, the structure is comprised of timber poles storing CO 2 for the life of the building. And then the actual thatch is also a natural CO2 storing product, but with an added advantage, being the fact that thatch grass is perennial. So, the thatch is expected to last for many years, during which time most of the CO2 is not released. By using thatch, the roof is therefore designed for present use but is also good for future recycling.

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Furthermore, dependence on resource-intensive products and materials is reduced. Thatch is an earth-friendly, recyclable material. It is a local, carbon-free material and by using thatch, we are truly supporting not only environmentally friendly construction, but also locally supplied materials. Thatching makes use of materials that are naturally obtainable, i.e. grass or reed. In South Africa, only certain indigenous grasses are typically used.

Due to global warming, temperature variations within seasons are becoming more extreme. More insulation products are brought onto the market regularly, but thatch still remains the most natural and eco-friendly solution. And, aesthetically, it is one of the most pleasing roof construction finishes. No other product has these two characteristics as a raw product.

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Photo credit: Alice

SAVINGS AND OTHER BENEFITS Thanks to the high thermal values of thatch, usage of heating and cooling is dramatically reduced and energy savings are guaranteed – good news with talk of ever-increasing electricity costs and possible power failures.

The myth of high costs for thatch roofs when compared to tiled roofs has also been busted in recent projects. Thatch is proving to be a most effective roof covering with many costing items taken into consideration. Thatch is a natural insulator that requires no thermal insulation, gutters or downpipes, nor fascias, soffits, ceilings, cornices, painting or other finishes.

Moreover, with a roof pitch of 45 degrees, a great deal of extra ceiling or loft space can be created, giving a building a strong sense of volume. With all these factors taken into consideration, a thatch roof is one of the most economical choices for a roof finish on the market.

Another misconception about thatch that is regularly proven to be incorrect is the ‘high’ cost of insurance. With various ways to incorporate fire protection systems into the roof, insurance is in fact brought down drastically by insurance companies.

There is no overnight cure to restoring our planet, but in going ‘green’ and by opting for a thatch roof as a more natural construction method and materials option, one is definitely on the right track towards making a difference.

MINIMUM TOTAL R-VALUES OF ROOFS As part of the overall calculations required by municipalities upon receipt of building plans, architects submit U-values and R-values (both are energy values). The U-value measures how effective a material is as an insulator, or its thermal conductivity.

The lower the U-value, the better the material is as a heat insulator. This thermal conductivity refers to how quickly heat is lost from it, and is measured in watts per m² per Kelvin.

The R-value refers to thermal resistance and is dependent upon the type of material, its density and thickness. Tiny air particles trapped in the insulating material resist the movement of heat (and cold). The higher the R-value, the better the insulation is at reducing heat flow.

A thatch roof functions as both an insulated roof and a ceiling.

The roof will ensure that the building is cool in summer and warm in winter, since thatch has a high insulation value. A thatch roof shall receive the minimum total R-value specified in the following table, for the direction of heat flow.

From the results of a test report ASTM C 518-10 by TTL dated 11 June 2013, the K-value of a thatched roof is: K = 0.056 W/ (m.K). The required thickness (D(m)) to comply with SANS10400-XA is therefore:

CLIMATIC ZONE 1

CLIMATIC ZONE 2

CLIMATIC ZONE 3

CLIMATIC ZONE 4

CLIMATIC ZONE 5

CLIMATIC ZONE 6

Minimum required R-value (m2 .K/W)

3.7

3.2

2.7

3.7

2.7

3.5

Minimum required thickness for thatched roofs (mm)

207

179

151

207

151

196

Direction of heat flow

Up

Up

Up & Down

Up

Down

Up

DESCRIPTION

D(m) = R(m2 .K/W) x k(W/(m.K)

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However, if the thickness calculations shown are less than the requirement in SANS10407-2015 Edition 2, the greater of the two shall apply. The difference in thickness will then have a positive energy influence on the building holistically.

The deemed-to-satisfy provisions are based on climate zones, including dry bulb temperatures, thermal neutrality, humidity and southern coastal condensation risk.

Thatching is a specialized field, and professional guidance and workmanship is essential to ensure a successful project.

The Thatchers Association of South Africa (TASA) is there to assist the public as well as architects, engineers and other professionals with any queries.

For more information, visit the TASA website at www.sa-thatchers.co.za.

OVERVIEW OF CLIMATIC ZONES ZONE DESCRIPTION 1

Cold interior

Johannesburg, Bloemfontein

2

Temperate interior

Pretoria, Polokwane

3

Hot interior

Louis Trichardt, Nelspruit

4

Temperate coastal

Cape Town, Port Elizabeth

5

Sub-tropical coastal

East London, Durban, Richards Bay

6

Arid interior

Upington, Kimberley

SOURCE REFERENCE AND CREDIT: A GUIDE TO THATCH CONSTRUCTION IN SOUTH AFRICA – 2016 Edition 1. © The Thatchers Association of South Africa (TASA).

BIGGARSBERG THATCHERS

Theunissen Thatching, a founder member of the Thatchers Association of South Africa, is a well established company. We specialise in all aspects of thatching and wooden structures.

BIGGARSBERG THATCHERS

Kosie Theunissen tel: 021 883 8383 cell: 082 854 5949 | tthatch@adept.co.za

Make the ‘Right Choice’ the first time!

Winner of the Best Thatch Roof in the World Award 2014

John: 083 270 3826 Shaun: 083 635 8746 Office: 034 651 1664 Email: thatchers@thatcher.co.za Web: www.thatcher.co.za

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B U L K I N S U L ATI O N

Higher electricity costs: Insulate well and pay less Following the most recent Eskom electricity price hike, and with winter just around the corner, we can all get ready to face higher energy bills. Domestic residences will be affected, but even more so will be large commercial and industrial buildings that must remain adequately heated on a larger scale. With proper insulation, you can avoid paying unnecessary costs by effectively reducing heat loss in your building.

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roof and ceiling that is poorly insulated can contribute up to 40% of the overall heat loss of a building during winter. A cost-effective way to significantly reduce this heat loss, and thereby reduce the building’s energy consumption, is to install a thermally efficient insulation blanket such as Romatherm ® into the ceiling or roof.

Whether installed within the ceiling void of a pitched roof or between the joists in the ceiling void of a flat roof, Romatherm ® offers substantial thermal benefits and cost savings.

Romatherm ® is a white polyester fibre insulation blanket, manufactured from recycled PET bottles (e.g. soft drink and water bottles). It is thermally bonded and an ideal choice for lay-on insulation for ceilings. And because it is available in roll form in various thicknesses, it is suitable for domestic, commercial as well as industrial applications. It is the optimal cost-effective insulation solution that provides excellent R-Values to satisfy the requirements under SANS10400-XA.

BENEFITS OF ROMATHERM ® • Tested by the SABS for thermal performance as well as for fire propagation.

Romatherm ® does not contribute to flame spread and is not toxic. It complies with SANS428 Fire Standards. (FTC15-148 B/B2/2) • Manufactured to ISO 9001—2008 (Reg LS4428).

• Can also be used as an acoustic dampener in roof applications.

• On flat ceilings, Romatherm ® can be laid in-between the trusses on top of the battens, or over the truss ties.

• Does not collapse over time – retains its ‘loft.’

• Friendly to the touch, will not irritate the skin, and does not affect breathing in any way – therefore is very easy to install.

• VOC free – no CFCs or HCFCs are used in the life cycle of this product (OPD =0%), and it is 100% recyclable.

Romatherm ® helps to secure a healthier living and working environment and at the same time reduces energy consumption and costs.

For more information, visit www.datlink.co.za.

THICKNESS

DENSITY

WIDTH

LENGTH

R-VALUE

TOTAL R-VALUE

40mm

10kg/m²

1.2m

10m

0.8

1.2

50mm

10kg/m²

1.2m

10m

1

1.4

55mm

6kg/m³

1.2m

10m

0.9

1.3

75mm

10kg/m²

1.2m

8m

1.9

1.9

100mm

10kg/m²

1.2m

6m

2.4

2.4

135mm

10kg/m²

1.2m

5m

3.1

3.1

100mm

11.5kg/m³

1.2m

8m

2.7

2.7

135mm

11.5kg/m³

1.2m

5m

3.1

3.5

145mm

11.5kg/m³

1.2m

5m

3.3

3.7

* Also available in 750mm wide rolls

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ROO F TI L E M AC H I N E RY

Semi-automatic roof tile extruder especially for Africa The SPS712 roof tile extruder has been developed specifically for remote projects within the African market.

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unique collaborative effort between Pan Mixers South Africa (PMSA) and ABECE of Sweden has brought about the SPS712 for the African market, where skill levels are low and proactive maintenance is not always a priority. With this in mind, the companies paid particular attention to detail in their development of this semi-automatic roof tile extruder.

FUNCTIONAL FEATURES One example is the dual start/stop function that requires the operator to use both hands to either start or stop the machine, thereby enhancing operator safety significantly.

To ensure ease of maintenance, as well as to keep the machine clean, the extrusion head flips upwards. All working parts are easily repairable and do not require special tooling to be removed.

The SPS712 utilizes an aluminium palette to shape the tiles. It can manufacture up to 5,000 concrete tiles in a nine-hour shift, depending on the specific plant configuration. This equates to about 10 tiles per minute.

The extruder features a heavy-duty design that incorporates high-quality materials and components in its manufacture. It has a 1.5kW motor power roller and a 5.5kW hydraulic power pack for the pusher movement. A stand-alone depalleter is also available, as well as ridge and trim tile manufacturing equipment. Yet it is easy to install, operate and maintain – important considerations with regard to remote project sites in Africa.

EASY TO OPERATE AND MAINTAIN Fredrik Toftemo, the ABECE Area Manager, explains that concrete is fed from a conveyor into the concrete hopper above the slipper and roller unit. Aluminium pallets are manually placed on the support rails that guide the pallets through the extruder. A hydraulic cylinder pushes the pallets through the release oil spray system and the making head in order to shape the concrete tile.

In collaboration with PMSA, ABECE has pioneered the SPS712 extruder for Africa.

The manufacturing process only requires three to five labourers, depending on the level of automation and the skill level of the staff.

“Combined with the fact that concrete roof tiles are such an eco-friendly product, the SPS712 extruder is the ideal machine for African conditions,” Quintin Booysen, Sales and Marketing Manager for PMSA, concludes.

Thereafter, the automatic knife unit cuts and shapes the tile.

This knife unit is kept clean by a water spray system.

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