Waterproofing is not just “some black stuff” which must be hidden, with people spending very little time, effort and money on it. That is a recipe for disaster.
Waterproofing is a very important element of a building, and the feeling amongst waterproofing professionals is that far more consideration and attention must be given to this element than what is often the case.
“Waterproofing should not be treated as just ‘some black stuff’ which must be hidden, with people spending very little time, effort and definitely not too much money on it. That is a recipe for disaster,” states Paul Koning, honorary member of the Waterproofing Association in Gauteng (WAG) and Chairman of the Roofing and Waterproofing Institute (RAWI).
In this article, WALLS & ROOFS takes a look at some of the challenges, causes for failures, and gets advice from industry professionals for a successful application.
The flat roof challenge
Why do people want to stay away from having a flat roof and have the perception that flat roofs leak?
“This conception is ill-founded,” says Koning. “Any roof type, whether tiled, slate, metal or fibre-cement sheeted roofs, as well as flat concrete or timber roofs, will leak if they are not designed and built correctly. Therefore one must understand where this reputation comes from.
“Flat concrete roofs are at a disadvantage from the start,” Koning notes. “On a building project, flat concrete roofs have to be waterproofed at an early stage so that the internal finishes can continue. These flat roofs then act as platforms to build scaffolding off, to store building materials, mix mortars and plasters on, access areas to work off and to dump rubble onto. Steep pitched roofs are not a problem because they cannot be used as platforms. Low pitched metal roofs can also take abuse from construction work above, but not as much as flat concrete roofs.”
Another problem that Koning points out, is that flat concrete roofs are where HVAC equipment, water storage tanks and other plant and equipment are installed, which means that maintenance staff will access the roof not only during installation, but over the life of the building, walking all over the waterproofing.
“What chance does the poor waterproofing have of surviving such use and abuse?”
The problem is not with the product
According to Koning, there are numerous good-quality waterproofing systems available for waterproofing flat roofs, from the popular “torch-on” membranes, self-adhesive membranes and PVC and EPDM membranes, to spray-on polyurea coatings and polyurethanes, as well as in situ acrylic and cementitious systems, to name but a few.
“It is important to be advised by reputable manufacturers, suppliers and specialist waterproofing contractors on the suitability of each system for different applications.
As long as good-quality systems are supplied and laid by a well-established, knowledgeable and reputable specialist waterproofing contractors, there would not be so many problems.” Koning states.
So what causes the leaks that give flat roof waterproofing a bad reputation?
• A lack of qualified waterproofers. Having a “bakkie”, ladder, bucket and brush doesn’t make you one.
• Little or no supervision by experienced and qualified waterproofing contracts managers.
• A lack of good standards and quality building work produced by the building contractor. This can be contributed to many the building contractors using labour only sub-contractors and relinquishing some control over the trained and qualified workforce.
• Poor or inadequate waterproofing detailing at the design stage.
• The total lack of care and attention, knowledge and understanding of waterproofing by all the other building trades.
• Flat roofs act as platforms for the rest of the construction work.
• The speed of contracts today. Screeds are not always dry enough before the waterproofing is laid.
• The lack of correct maintenance.
As a professional, Koning presents waterproofing workshops for architects and students in his quest to improve waterproofing standards in South Africa.
He points out that the current statutory documents on waterproofing are SANS 10400 Part L Roof, section 4.3 of the National Building Regulations. “The latest publication of November 2011, which is a great improvement on the previous National Building Regulations, and is currently still being fine-tuned to produce a worthwhile and useable document for waterproofing,” he says.
“There is also SANS 10021, previously SABS 021 Waterproofing of Buildings (Damp-proofing and Vapour Barriers), which has not yet been properly revised since 1998. Currently this document is being revised and should be another valuable document when it is finally gazetted.”
Another good read Koning suggests, is The Waterproofing of Buildings, which is a very helpful guide to waterproofing.
“It is very encouraging to know that there are voluntary waterproofing bodies that take education and training very seriously, especially the Roofing and Waterproofing Institute (RAWI),” Koning adds. “RAWI regularly holds workshops and training sessions sponsored by manufacturers. Through RAWI, workers can be assessed for prior learning and go on CETA approved waterproofing training programs at a certified CETA training academy. Unfortunately, currently this is only available in the Western Cape.”
Tips for getting waterproofing right
“Simply put, it is about education, training and supervision,” states Koning.
He suggests that the subject of waterproofing should be taught at tertiary level and should form part of the curriculum in all building disciplines.
In addition, it is important that architects and engineers get their initial design and detailing of the waterproofing correct at the drawing board stage. This may also influence structural considerations.
With a wide variety of waterproofing systems available in the South African market, system selection is another important aspect, taking into account the situation, the interface with other building elements and the finished product required.
“The manufacturer or supplier of the waterproofing system must be national, well established, with a track-record of good service, and have very knowledgeable and qualified representatives. The company must also be involved with the specialist contractor during the contract and application of their waterproofing systems, accepting and approving the substrates and the application, and signing off the works end of the contract,” Koning recommends.
In addition, the specialist waterproofing contractor must be knowledgeable, experienced, employ highly qualified and trained artisans, be financially sound and have the infrastructure to carry out the job. Skilled contracts managers should supervise the contract on a daily basis and raise issues before they become a problem so they can be addressed correctly.
What about guarantees?
“The old saying that guarantees are not worth the paper they are written on, is not far from the truth,” states Koning. “Don’t be fooled by a guarantee and the long guarantee periods. They are not unconditional that the roof will not leak.”
He explains that the materials have a manufacturer’s product warranty which only covers the manufacturing of the material that it will not be defective or deteriorate prematurely, while the specialist contractor offers a workmanship guarantee that the material has been laid or applied in strict accordance with the manufacturer’s instructions and methods.
Waterproofing at the coast
When it comes to selecting and applying waterproofing systems in coastal regions, Gavin Prinsloo, chairman of the Waterproofing and Roofing Association in the Cape (WARAC), says there isn’t much difference from doing it inland.
“The sea air makes no difference to the waterproofing products; however, it does make a difference to the sheet metal roof covering. Coastal areas require a roof sheeting with a better protective coating to protect it against rust corrosion,” he points out.
One thing that may be a bigger factor at the coast than inland is wind. “In my opinion, waterproofing systems applied in coastal areas need to be more thorough than waterproofing systems inland, for no other reason than the wind. Coastal areas have greater wind exposure when it rains, causing the rain to blow horizontally and not just gently falling downwards. This wind-driven rain tends to find its way through vertical surfaces, which wouldn’t happen in windless rain,” he explains.
“The heat and exposure to the sun are other factors to consider when choosing a waterproofing system. Some systems cannot be exposed to the sun and need to be covered or protected in some way,” Prinsloo adds.
Where to go to . . .
There are several associations in the industry that work to support responsible waterproofing contractors, suppliers and manufactures, but also act as consumer watchdogs.
According to Tony Colvin, executive chairman of the Waterproofing Association of Gauteng (WPAG), the association’s role is to get like-minded waterproofing contractors and suppliers on the same page, and ensure that members do not let their customers down and overcharge for shoddy workmanship and use of inferior materials.
“One of the biggest problems we encounter when dealing with the public is ignorance – great expectations of what the customer believes he should be getting from the contract and apportioning blame,” he says.
“The waterproofing contractor is there to apply a product to a situation and is not responsible for faulty design of the original structure. Obviously the waterproofing contractor is regarded as an expert and frequently is in a position to offer advice. However, advice is not always taken (especially when the result is expensive or unsightly) and when the client is unhappy with the end-result, he blames the contractor. When approached in cases like this, the association tries to resolve the issues amicably and to everyone’s satisfaction,” Colvin explains.
Scrutinising new products
Colvin further notes that new products are constantly coming onto the market from all over the world, carrying many accolades. However, the fact is that the biggest part of South Africa is thousands of metres above sea level and closer to the equator than the whole of Europe and many other countries that manufacture and install waterproofing on exposed roofs. Consequently buildings here are subject to much higher levels of ultraviolet (UV) degradation.
“We also share information regarding products coming onto the market, whether of proven quality or not. Through the national body we provide information to the South African Bureau of Standards (SABS) and other authorities regarding correct specifications to minimise future problems,” he concludes.
Words of advice
Tony Colvin, WPAG: “Our advice to specifiers is to not be taken in by fancy sales talk, and to check carefully the reputation and credentials of the suppliers recommending a product or system.”
Full thanks and acknowledgement are given to Paul Koning of KVB Associates, the Waterproofing Association of Gauteng, the Roofing and Waterproofing Institute and the Waterproofing and Roofing Association Cape for the information given to write this article.
Caption: The waterproofing system used on the roof and parking deck at 2 Military Hospital included: a bitumen primer with two layer of 4mm torch on membrane, covered with a dimpled high density polyethylene protection membrane below insulation, a sand bed and interlocking pavers.
Courtesy of a.b.e. Construction Chemicals