Bathroom Waterproofing Done Right: Step-by-Step Before You Tile

Bathroom leaks are one of the costliest repairs in a home, because fixing them means breaking tiles, often damaging the ceiling of the flat below and redoing plumbing. Almost all of them can be prevented with an hour of attention before tiles are laid.

The rule: tiles and grout are not waterproof. Water passes through grout lines over time. The real protection is the waterproof layer underneath, plus a floor that slopes to the drain.

The correct sequence

1. Finish plumbing first. Pressure-test all concealed pipes for leaks before covering them.
2. Prepare the base. The floor slab and walls should be clean, sound and free of loose material.
3. Make a coving. Round off the corner where the floor meets the walls with mortar. Sharp corners crack and leak.
4. Seal pipe penetrations. Wrap around floor drains and pipe outlets with a fabric reinforcement embedded in the waterproofing.
5. Apply the waterproofing. Two coats of a suitable cementitious or polymer membrane, brushed in perpendicular directions.
6. Take it up the walls. Commonly about 300 mm on all walls, and much higher, often full height, in the shower area.
7. Flood test. Plug the drain, fill the floor with a few centimetres of water and leave it for a day or two. Check the ceiling below and adjacent walls.
8. Protective screed with slope. Lay screed falling towards the floor drain, then tile.
9. Grout with epoxy in shower areas, which resists water and stains better than cement grout.

Sunken bathrooms need extra care

Many Indian homes have sunken bathroom slabs filled with brickbats or lightweight fill. If water gets into this fill, it collects and seeps for years. Waterproof the sunken portion fully before filling, consider a second waterproofing layer above the fill, and provide a weep pipe where the design allows.

Signs of a failing bathroom

• Damp patches on the ceiling below or walls next door.
• Dark, crumbling grout lines.
• Tiles sounding hollow around the drain.
• Persistent musty smell.

Not sure where your damp is coming from? Our damp walls guide helps you find the source.

Frequently asked questions

Can I waterproof without removing tiles?

Penetrating sealers and epoxy regrouting can slow minor leaks, but a failed membrane under tiles can only be properly fixed by retiling.

How long does good bathroom waterproofing last?

Done correctly and protected by tiles, it should last as long as the tiles themselves.