Tanking is the waterproof layer applied behind the tiles in a shower or wet area, before tiling begins. It is what keeps water out of the wall and floor structure.
Why tile and grout are not enough
Tiles are waterproof on the face, but grout is porous, silicone joints age, and tile edges and corners let moisture through over time. Without a membrane behind them, that moisture reaches plasterboard and timber — and the first you know of it is a stain on the ceiling below.
Where you need it
- Any tiled shower area — enclosure or walk-in.
- Wet rooms — the whole floor and the splash zones.
- Around a bath with a shower over, at least to the splash zone.
If a quote for a tiled shower does not mention tanking, ask why. TileDegree photographs the tanking and sends it to you before tiling over it.
Published 18 February 2026.