Encouraging a more holistic approach to waterproofing

“When we reviewed photographs of the wet areas in the bathrooms under construction, we found major faults,” O’Mara said. 

“While we could see a great level of care had gone into the application of the waterproofing membrane, we noticed that the product on the floor was one colour and the product on the walls was a different colour.”

An inquiry to the builder revealed waterproofing products from two different manufacturers had been used in the bathrooms.

The team also noticed the wall linings weren’t fixed with screws but had been glued on, meaning the substrate would eventually fail under the weight of the tiles.  

“Although the level of workmanship in terms of the waterproofing application was some of the best we’ve seen, they used the wrong products,” O’Mara said.

“Plus, no matter how good the waterproofing is, if the substrate fails, the waterproofing is not worth anything. The result was the developer pulled out all the bathrooms and started again.” 

A more holistic approach to waterproofing

Many waterproofing issues stem from the fact it has traditionally been viewed in isolation from the broader building design. This means there has been little consideration given to how a waterproofing membrane will interact with adjoining sections of a building, or the impact of building deflection on drainage.

This lack of integration needs to change, said Engineers Australia Fellow and Chartered engineer Michael van Koeverden FIEAust CPEng, Director of CQT Services.

A past President of Engineers Australia’s Newcastle Division and ast National President of the Concrete Institute of Australia, van Koeverden is Engineers Australia’s representative on a committee convened by the NSW Building Commissioner to improve waterproofing practices. The group will produce technical specifications for waterproofing and development of a formal waterproofing qualification.

“The reason it’s become so apparent that training is needed is because of the extent of water damage in new buildings, and the way waterproofing has been treated in the past,” he told create.

“In many cases, people consider a waterproofing membrane to be a waterproofing solution. We are moving towards a more holistic approach and a new definition of waterproofing, where it’s the collection, redirection and drainage of water, rather than just the application of waterproofing membranes.”

A more integrated approach is also important as the standard for concrete structures (AS 3600:2018: Concrete Structures) requires a design life of 50 years, while waterproofing membranes can last as little as 10 to 15 years.

“We have a potential disconnect between the waterproofing provided by the membranes and what the structure is required to do,” van Koeverden said.

“Future designs will be required to nominate 10-year deflections, joints will need to be identified clearly on drawings in terms of what their role and function is, and part of the engineers’ responsibility is to provide a design that’s capable of meeting the requirements for waterproofing.”