Leaking showers and Waterproofing Defects are the most common Defects we find in Sydney Homes.
It may surprise people to learn, that the most common building defect, is also one of the most expensive to fix – leaking showers and membrane defects.
Based on experience, we find most showers start leaking after 10-15yrs due to failure of the waterproof membrane behind the tiles.
What is a Waterproof Membrane?
A waterproof membrane is a vital part of ‘wet area’ construction that prevents water from penetrating into the surrounding building elements. ‘Wet areas’ are rooms that require the installation of waterproofing such as bathrooms, toilets, laundries and behind basins. The waterproof membrane must be installed by a suitably licensed waterproofing contractor. When complete the work should come with a written certificate to ‘certify’ the work in case of future problems. Normally a warranty should apply for 6 years from the date of installation / construction. Waterproofing certificates are usually required as part of the ‘Occupation Certificate’ when major renovation work is done or with new dwellings – at the time of completion. The occupation certificate (OC) is the ‘over-arching’ building certificate obatained when all work has been satisfactorally completed. An occupation certificate relies on the waterproofing certificates as part of the completed doccumentation. The building inspection report may recommend obtaining a copy of the certificates where possible and relevant.
A waterproof membrane is usually installed below the tile screed, which is the graded sand and cement floor topping layer installed in bathrooms to achieve a slope towards the drainage with tiles. (tiles are installed on top of the screed once it hardens).
Waterproof membrane products in domestic bathrooms are usually a thick paint-on polyurethane material that hardens to form a thin waterproof layer. Subsequent materials are installed over the top, such as tiles. The membrane covers the floors in all areas with an upturn of at least 150mm at the lower walls. In the shower the membrane must continue high up the walls as well as around bath tubs and behind basins. To understand the membrane requires thinking about the bathroom floor and lower walls forming a ‘tank’ or ‘tray’ that can hold water until it has drained away. Aluminium ‘L’ angles are installed below the tiles in two main locationns: 1 – around the footprint of the shower recess (under the base of the shower screen). This is the main tray intended to keep most water inside the shower cubical, trying to stop water spreading out accross the bathroom floor. The second aluminium angle is installed in the door threashold to prevent water seeping out the bathroom door way. Reinforcing tape is applied with the wet waterproofing material where the membrane passes from floor to wall or around angles and in corners. The fabric helps to ‘bridge’ these different areas and profide reinforcement where building movement might occur during the life of the building.
Membrane section – no screen
Membrane section – level shower floor
Membrane section – floor drain detail
Membrane section – hobbed shower
Where and Why do Waterproof Membranes Fail in Bathrooms?
Based on experience the most common areas for membrane failure in bathrooms include the following:
- Bathroom door threshold. This is possibly the most common area for waterproof membranes to fail. This is where water seeps out through the door threshold of the bathroom, causing damage to the adjacent flooring materials. Usually water seeps out from the shower and across the bathroom floor (under the tiles) eventually seeping out where the floor angle is installed.
- Shower tap wall penetrations. Also very common, the tap bodies are a common point of failure of the waterproof membrane. The tap must pass through the tile, membrane and wall substrate to connect to the pipes inside the wall. A combination of reinforcing tape and gaskets are needed to waterproof around the metal tap bodies. Usually these taps are under the main stream of water in the shower and are an obvious point for water to collect. Copper, steel, brass, plastic, tiles, timber and masonry are all common materials found at the point of membrane pentration. These different building materials will expand and contract at different rates, causing ‘differential’ movement and opportunity for the membrane to fail.
- At the junction between the floor and wall tiles or inside the internal vertical corners. Again these junctions between different building materials and different wall sections are a common source of movement leading to cracks in the membrane. A combination of flexible sealant, foam bond breakers and reinforcing tapes are installed under the waterproofing in corners and around drainage pipes. Failure here can result from excessive or unanticipated movement.
- The shower floor drain connections – Especially common with large architectural drains but also with 100mm round floor wastes, we often see leaking below bathroom areas originating from the shower drain pipe. Obviously a point of concentration for water, the waterproofing membrane must continue down into pipes and bew fully reinforaced around drainage collars. This is commonly not done properly and is evident by the collection of minerals below the drainage pipe.
Factors such as installation defects or building movement are the main causes for membrane failure.
What can be done to repair a leaking shower?
Where significant leaking is occurring, the best recommendation is to completely renovate the bathroom, which is required to replace the membrane properly and in accordance with ‘wet area’ building codes and the waterproofing standards AS 3740. The problem with this advice is the high cost associated with a bathroom renovation. Bathrooms are one of the most expensive rooms in the house due to the large number of trades involved to make it happen and the compliance regulations. A standard bathroom is in the vicinity of $25K-$30K, but architectural or bespoke high end bathrooms can cost between $50K-$75K or more.
Asside from a bathroom renovation, there are other repair options that can prolong the life of the bathroom, however leaking typically returns in these cases. Repairs such as retiling the shower recess or installing a sealant repair are common attempts to prevent water penetraiton. These can be done for a fraction of the cost of a bathroom renovation but are not permenant solutions.
Leaking shower, membrane defect
leaking shower high moisture readings
Leaking shower drain under floor, subfloor view
