A wet room is the most technically demanding project a tiler can take on — and the most rewarding when it’s done well. Waterproofing, substrate, drainage, fall, and tile specification all have to work together. Here’s the process we follow on every installation.
What Makes a Wet Room Different
A traditional shower has a tray. A wet room doesn’t — the floor of the room IS the shower tray. That means every square centimetre of floor and the lower walls need to be fully waterproofed, with careful fall to a drain and no raised threshold between the shower zone and the rest of the room.
Substrate and Subfloor
Ground-floor wet rooms typically go over a cementitious substrate — ideally a screeded floor tanked and overboarded with cement-bonded board. Upper-floor wet rooms over timber joists need a more careful build-up: 22 mm plywood, fully screwed at 150 mm centres, then tilebacker board bonded and screwed over that.
Tanking: Liquid vs Sheet Membrane
We prefer liquid tanking systems on complex geometry and sheet membranes on simple rectangular rooms. Both work; the trick is detailing at corners, penetrations, and the drain union — that’s where failures happen.
Drain Selection
Linear drains are now standard on almost every wet room we build. They allow a single-direction fall (1:80) instead of the four-way fall that a centre-drain puck demands, which simplifies the tile layout dramatically.
Tile Layout and Fall
Large-format tiles look fantastic in wet rooms but demand a perfectly flat substrate. On most jobs we specify 600 × 600 porcelain for the floor and larger formats on the walls. Walls get a 1 mm adhesive comb, floors get a 6 mm notched trowel — and every tile gets back-buttered.
Timing and Budget
A typical domestic wet room takes us 2–3 weeks from strip-out to handover, depending on scope. Budget conservatively: a proper wet room (full tanking, linear drain, large-format tiles, matched hardware) is £8,000–£15,000 depending on the London postcode and material spec.
Common Mistakes
- Under-specifying the drainage. A single 50mm waste on a 2.5 × 3 m wet room is too small — upsize to 75mm.
- Running cold on tanking. £200 of extra membrane is always cheaper than a £5,000 repair two years later.
- Ignoring underfloor heating. Heated stone or porcelain transforms the user experience; it’s always worth the extra wiring.
