Bathroom & Toilet Waterproofing

This treatment is specified where the inspection shows it is the right answer for the problem found.

Where it applies. Bathroom, toilet and shower floors and wet walls, in new construction before tiling and in existing bathrooms where leakage is showing on the ceiling or wall below. It applies once plumbing has been proved sound — there is no waterproofing system that resists a live pipe leak, so an isolation test comes first and any defective line is corrected before we start.

Preparation. Tiles and screed removed to the structural slab across the full wet area, not just the visibly failed part. The slab is checked for fall toward the drain and re-screeded if it runs the wrong way. Cracks cut out and filled. A coved fillet formed at every wall-to-floor junction. The drain body is exposed so the membrane can be dressed into it. Every pipe penetration — supply, waste, floor trap, shower mixer — is cleaned so a sealing collar can be fitted individually rather than the annulus being packed with mortar. Salt-contaminated plaster on affected walls is cut back beyond the damp line.

Application. A cementitious polymer-modified or PU tanking membrane, brush or trowel applied in two coats at right angles, with reinforcing tape bedded into the first coat at all junctions, corners and penetrations. On the floor it covers the full area and is dressed into the drain. On walls it is taken up to at least 300 mm as standard, to 1,800 mm or full height in the shower zone, and continuously behind any wall-hung fixture. Coverage is applied to the specified kg per m² rather than to visual coverage.

Curing and programme. 4 to 12 hours between coats. The membrane is ready for flood testing at 48 hours and ready to tile after the test passes — realistically a bathroom is out of use for 5 to 7 days including tiling and grouting. Tiling directly onto a membrane that has not cured is a common site shortcut and it debonds.

Testing and warranty. The drain is plugged and the floor flooded to 25 mm for 24 hours, with the ceiling below observed throughout. Where the bathroom sits above another flat we arrange for the owner below to be present at the test, which also settles the question of liability. Tiling begins only after a pass. Eligible completed work carries Leakproofs by Betterwork’s written ten-year warranty on the treated area, with exclusions stated on the estimate.