Roeland Trietsch from Melbourne Polytechnic advocates for waterproofing standards in domestic wet areas to be updated.
Originally created in 1989, the Waterproofing Standard of domestic wet areas (3740-2010) is focussed on internal waterproofing applications. The latest version of this standard was released in 2010 and I believe is well overdue for revision.
The design of internal wet areas has changed significantly in recent years along with the use of different construction materials within internal wet areas. For these reasons, I believe this standard be reviewed.
According to this standard, the following areas are considered domestic wet areas: bathrooms, showers, laundries and sanitary compartments.
Clearly mentioned in the introduction, it sets out the minimum requirements for materials, design and installation of waterproofing for the areas mentioned above. My approach to any waterproofing application is to go above and beyond, to eliminate potential failures in the future. This standard should also ensure a high standard of application, and I have some suggestions that may be beneficial to the overall outcome of a waterproofing application.
Firstly, the definition of a wet area should be amended. A kitchen has the same risks associated with a water leak as a laundry. A dishwasher and a washing machine both have a water connection and should be treated the same way. Both types of appliances have plastic elbow water connectors that are quite fragile and could snap off or crack due to over tightening. A mandatory waterproofing system including a floor with fall and a floor waste (to collect and divert the water towards drainage) should be installed in both scenarios.
The standard allows professionals to install a membrane system below a screed in a shower. In my experience, I would always sandwich the screed between two membrane systems; one below and one above the screed. This should protect the screed from being saturated with moisture and avoid a common issue within any wet area; efflorescence. Even though I always recommend using washed sand for a screed, there is a risk for salt and mineral deposits appearing in a wet area. Especially when using dark coloured cementitious grout.
Another concern is the waterproofing requirement for the walls within a shower. Currently the minimum height of a waterproofing membrane is 150mm above a finished floor level and the internal wall junction to be waterproofed up to 1800mm high and 40mm wide on either wall side. The rest of the wall surface is required to be water resistant.
I have seen shower walls leak due to moisture travelling through the grout and slowly saturating the substrate below and escaping the wet area. Best practice should be the bench mark, not the minimum requirement. As a result, I would always recommend the entire wall surface to be waterproofed to ensure a quality install of a waterproofing system.
New design trends are implemented within wet areas without clarification by the current standards. An example of this would be the common use of large rain heads that are often part of high-end shower designs. Is the 1800mm high membrane going to be sufficient is this situation? Or do we have to extend the membrane to the ceiling height?
Many of my students are looking for clear information within this standard but sometimes it generates confusion. The “grey” areas should be eliminated and provide waterproofing applicators with clear instructions.
My final suggested amendment to the standard relates to the unrealistic scenario of waterproofing a floor to 1500mm from the shower connection on the wall and terminating the membrane with a curved waterstop in the floor. This is the rule for concrete and compressed fibre-cement sheet flooring.
Installing a curved waterstop in a tiled floor scenario would make a tiler’s job difficult and time consuming. The finished result would also be very unsightly. In my opinion, end-users are better off waterproofing the entire floor surface to protect the substrate below and have an aesthetically appealing result. A bathroom floor with fall incorporated would be even better!
Despite a few recommendations and improvements, the standard still provides a great deal of information for waterproofing applications within internal wet areas.
About the author
Roeland Trietsch has been working in the waterproofing industry for many years, running his own business. Three years ago, he has transitioned to teaching Certificate III in Construction Waterproofing at Melbourne Polytechnic.