Waterproofing – back to basics

by Tania Wannenburg
Waterproofing back to basics

Three waterproofing experts give us the basics of getting waterproofing right from the start.

Waterproofing is a very specialist area of construction and if the initial application is not done correctly, repairs are imminent.

To get back to basics, WALLS & ROOFS asked several experienced waterproofing experts to give us the gist. We hear from Peter McArdle, specification consultant at Mapei, Harry Govindsamy, customer technical services at Sika, and Gordon Anderson, one of South Africa’s most experienced waterproofing authorities, currently consulting for a.b.e. Construction Chemicals, part of the Chryso Southern Africa Group.

What are the key areas in a building that require waterproofing?
Both the external and internal areas of residential and commercial properties require efficient waterproofing. External areas are areas that are exposed to the elements such as roofs, balconies and terraces. Internal areas include showers and bathrooms and, in commercial developments, gyms, showers, kitchens, water features and planter boxes.

Which areas are often overlooked?
Showers, balcony slabs, flat concrete roof slabs and parapet walls are areas that are very susceptible to leaks because often waterproofing products are not specified or quoted for, so it is not done upfront.

If waterproofing was specified, why does it fail?
The reasons for waterproofing failures are legion, but in my experience the following are the most pertinent:
•    Incorrect, vague or poor specification.
•    The wrong choice of material for the application.
•    A slow uptake of new products in the waterproofing field by specifiers.
•    Poor or incomplete detailing.
•    Failure to recognise that waterproofing is a specialist trade.
•    Good, recognised specifications are too easily overturned by main contractors.
•    The appointment or use of untrained or poorly trained waterproofing sub-contractors.

Damage to installed weatherproofing systems and poor design are two of the main causes of leaks in buildings. My experience commonly indicates that damage to an installed waterproofing system is the prime offender when it comes to leaks. Such damage is often caused by trades or workers having scant regard for the waterproofing.

For example, often when television aerials are installed, the relative wiring is secured by nailing through the waterproofing, with the fitting of lightning arrestors being another regular cause of problems. Hammering nails through the waterproofing system can have only one result, namely leaks.

We often see poor application or the use of incorrect products resulting in the waterproofing failing, especially on balconies, flat concrete roofs and shower areas. If the waterproofing hasn’t been specified in detail upfront, we find that the contractors do not apply the full waterproofing system and that is where it goes wrong.

What is your advice for getting waterproofing right?
Invite the architect or QS to sit with specifying specialists from recognised material manufacturers at the outset of a project to determine which would be the most satisfactory, cost-effective and long-lasting solution. Don’t settle for the “What did we use/do last time” solution, which is too often the case.

For successful waterproofing, input from experts should be sought. A competent and experienced architect or designer working with an efficient builder will guide property owners through the pitfalls. The specified waterproofing systems must be appropriate and made with the full knowledge of the substrate and what will be applied on top of it. Without this information, there will be a risk of failure due to the wrong materials being used in the wrong place.

In addition, the selection of the waterproofing applicator is important. The company selected should have a verifiable track-record.

Make sure that the correct product is selected for each area that needs to be waterproofed, and follow the application directions. If it is done correctly as per the manufacturer’s instructions, then there shouldn’t be any reason for failure.

How long does waterproofing last?
Depending on which products are specified, waterproofing can last anything from five to 20 years. However, if you select a waterproofing solution with a guarantee for ten years, you have to be prepared to waterproof again after that period of time.

What is new in the waterproofing industry?
There are so many new products and technologies available in the world today, but the uptake in South Africa seems very slow. Although many new products may well have EN, DIN or other certifications, they do not have a South African Bureau of Standards (SABS) mark yet, something that is often asked for. If our SABS and CSIR institutions were better funded and more efficient, I am sure the uptake of new technologies would accelerate.

No need for headaches
“Waterproofing does not have to be a problem,” adds Anderson. “By using quality and trusted materials – and paying attention to detail – a good result will be achieved.”

Full thanks and acknowledgement are given to a.b.e Construction Chemicals, Mapei and Sika for the information given to write this article.

McArdle’s checklist for waterproofing a building:
1.    Roof.
2.    Basement.
3.    Ground floor slab (if no basement).
4.    All areas around entries:
a.    Windows.
b.    Doors.
c.    Pipes and ducts.
5.    Bathrooms and showers.
6.    Kitchens.
7.    Balconies on multi-storey buildings.

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