One of the most common non-compliant items in new builds or renovations is a bathroom. The usual cause of the problem is badly performed waterproofing that causes failure of the membrane and leaks out of the shower recess or wet area.
Some licenced waterproof technicians do not know what they are doing. Some technicians don’t seem to care if the job is not compliant to AS 3740. As long as it looks good enough for them to get paid and go onto the next job.
There are many things that may not done correctly. A leak control flange for floor penetrations may not be fitted or may not be fitted correctly.
Corners and junctions must have a bond breaker. This allows for movement and elongation of the membrane without it failing.
The entire area must be dust free before the application process. The area to receive the membrane must be primed with the correct primer. The membrane must be suited to the application and the substrate.
If water does escape the shower recess there is a secondary water-stop at the doorway that has the membrane terminate to it. The membrane will be covering the floor and also 150mm up the walls to provide an impervious barrier to water. Any water that may be under the tiles is then contained in the wet area and does not damage the rest of the house.
In short, once the membrane has been tiled over it is impossible to ascertain the standard of work that has been performed. Because a membrane system has been designed and formulated to have tile adhesive stick to it really well tiles cannot be removed without damaging the membrane. The wall sheeting will also tear away as the membrane stick to it really well. There is no cheap repair for a leaking membrane. The tiles, wall and floor sheeting and membrane will all have to be reinstated.