Bathroom Waterproofing

Waterproofing is the only part of a bathroom that is completely invisible once the job is finished and the only part whose failure takes the wall frame, the floor structure and the room next door with it. It is also, for exactly that reason, the easiest place in a renovation to save a few hundred dollars without the customer ever knowing.

What the standard actually asks for

Waterproofing of domestic wet areas is governed by an Australian Standard, and it is more specific than most people expect. It sets out which surfaces have to be covered and to what height, how junctions between surfaces are treated, how penetrations are sealed, and what the substrate has to be before anything is applied.

The parts that matter in practice are the junctions, not the flat areas. A membrane rolled across an open floor is the easy bit. Where bathrooms fail is at the wall-to-floor junction, at internal corners, around the waste, where the tap bodies and the shower rail penetrate the wall, and at the edge of a hob or a step-down. Those points move slightly as a building moves, which is why they are bonded with flexible detail rather than simply painted over.

The other requirement people underestimate is the substrate. A membrane bonds to what it is put on. Applied over a dusty screed, an unprimed sheet, or a surface that is still holding moisture, it will do exactly what it is asked to do and then let go.

Falls, and the reason they come first

A membrane is a barrier, not a drain. Any water that reaches it has to be led somewhere, so the floor underneath has to fall to the waste before waterproofing begins.

This is the sequence step that gets compressed when a job is running late, and it cannot be fixed afterwards. If the screed does not fall correctly, water sits on the membrane under the tiles indefinitely. The bathroom will look perfect and will slowly saturate the tile bed, and the first symptom is usually staining in the grout that no cleaning will lift.

Cure time is not padding

Once the membrane is on it has to cure to its full film thickness before anything covers it. Depending on the product and the conditions that is a real wait, and in the humidity here it can be longer than the tin suggests, because the coating gives up its moisture more slowly when the air is already carrying so much.

Tiling onto a membrane that has not fully cured is completely invisible at handover. It is one of the most common reasons a bathroom that was renovated properly in every visible respect starts leaking in its second or third year.

We build the cure into the program rather than treating it as slack, and the wet area is inspected before tiling starts.

The certificate

At completion you get a certificate recording what was applied, where, and by whom. Keep it. It is what you hand a purchaser, an insurer or a body corporate when the question comes up, and on a unit it is often the document that decides whether a claim is entertained at all.

For waterproofing as part of a larger job it is included in the scope rather than quoted separately. If you are chasing an existing failure instead, start at leaking shower repairs, or call 0468 047 067 and describe what the room is doing.