Wet rooms
Wet room tanking: the layer that keeps the water in
What tanking is, where it goes, and why it matters more than the tiles on top.
A wet room has no shower tray. The floor itself is the tray, so the whole room, or at least the wet zone, has to be waterproof beneath the tiles. That waterproof layer is called tanking, and it is the part of a wet room nobody ever sees once it is finished.
Our wet room page puts it plainly: every wet room starts with the parts you cannot see. This guide explains what those parts are, so you know what to ask about before anyone quotes you.
Why tiles and grout are not waterproof
It surprises people, but tiles and grout alone do not stop water. Grout is porous, and fine cracks appear over time. In a room with a tray, that barely matters. In a wet room, water sits on the floor every day, so something beneath the tiles has to stop it reaching the boards, the ceiling below or the walls.
Where tanking goes
Tanking covers the floor and runs up the walls in the wet area, with particular care at the junctions. Corners, the joint between floor and wall, pipe entries and the drain itself are where failures happen, so these get reinforcement rather than just another coat.
- Across the whole floor of the wet zone
- Up the walls around the shower area
- Reinforced at every corner and wall to floor joint
- Sealed around pipes, valves and the drain body
Falls come before tanking
Water has to run to the drain without pooling. That means building the floor with a gentle, consistent slope before the waterproofing goes on. Our gallery shows both styles we fit: a linear drain along one edge and a floor tiled down to a centre drain. Each needs the falls set out differently, and the choice affects how the tiles are cut.
Get the falls wrong and water sits in puddles on top of perfect tanking. Get the tanking wrong and the falls send water exactly where you do not want it. Both have to be right.
The floor underneath
Timber floors move slightly, especially upstairs. A wet room on a timber floor needs a rigid, stable base so that movement does not crack the tanking or the tiles. This is assessed at survey, because it can change the scope of the job.
What to ask any wet room installer
Because none of this is visible at the end, it is worth asking directly how it will be done. A good answer is specific, not vague.
- How will the floor be prepared and made rigid?
- Where exactly will the tanking go?
- How are corners and the drain detailed?
- Which drain position suits this room and why?
How tanking fits into the order of work
Tanking sits in the middle of a wet room job. First the old room is stripped and the floor is made rigid. Then the drain is positioned and the floor is built with its falls. Only then does the waterproofing go on, and it is allowed to cure before anything is fixed over it. Tiling comes last, followed by the glass screen and sanitaryware.
Rushing any of those stages to save a day is the most common reason wet rooms fail. Because the tanking cannot be inspected once it is tiled over, we treat that stage with extra care and are happy to explain what has been done before the tiles hide it for good.
Questions
Frequently asked
Is tanking really needed if the tiles are good?
Yes. Tiles and grout are not waterproof on their own, and a wet room floor gets wet every day.
Does tanking go on the walls too?
Yes, around the wet area and with reinforcement at corners and wall to floor joints.
Linear drain or centre drain?
Both work. The choice depends on the room shape and the look you want, and each needs the floor falls set out differently.
Can a wet room go on an upstairs timber floor?
Often yes, once the floor is made rigid and stable. This is checked at survey.
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