Backgrounds and Preparation · 4 lessons

Wet rooms and tanking explained

2 min read · self-test time extra

Tiles keep most water off, but grout lets some through. Tanking is the waterproof layer behind the tiles that stops it reaching the wall or floor.

Our wall and floor tiling path is in public beta: some lessons are still being checked.

What tanking is

A waterproofing system goes on before the tiles: a liquid membrane, a sheet membrane or a waterproof board system, with tapes for joints and corners and seals round pipes. Use one maker's system and follow its instructions.

Where it goes

In a shower, everywhere that gets soaked: the walls round the tray or floor area and up past the shower head. Plasterboard and gypsum plaster are damaged by water, so behind a shower they need protecting or replacing with a suitable board.

Wet rooms

In a wet room the whole floor is tanked and falls gently to a drain, and the membrane turns up the walls. Getting the fall right happens before the tiles go down.

The plumbing comes first

Moving the waste, the water pipes or the toilet is plumbing work, done before tanking starts. Some water fittings work also needs your water supplier's permission first.

Common mistakes

Trusting tiles and grout to keep water out on their own.
Mixing membranes, tapes and adhesives from different makers' systems.
Skipping the tape at board joints and internal corners.

The lessons this guide comes from

Tanking and wet rooms
Movement joints
Uncoupling membranes
Underfloor heating