Wet room waterproofing (tanking) explained
Tanking is a waterproof layer applied to the walls and floor of a shower or wet room before tiling. Tiles and grout are not waterproof on their own, so the membrane behind them is what stops water reaching the structure. Corners, joints and the area around the drain are the critical details.
Aren't tiles and grout already waterproof?
No. Cement grout absorbs water and joints can move over time, so water finds its way behind the tile. In a normal bathroom the substrate can usually cope, but in a shower enclosure or open wet room a proper waterproof layer under the tiles is the only reliable protection.
What does tanking involve?
The work is done in stages before a single tile goes on:
- Make sure the substrate is sound, dry, rigid and suitable for tiling.
- Prime the surfaces so the membrane bonds properly.
- Reinforce internal corners, wall-to-floor junctions and pipe penetrations with tape or collars.
- Apply the membrane system to the manufacturer's coverage and coats.
- Let each coat dry fully before the next, and before tiling.
How far up the wall should tanking go?
As a rule, the whole shower enclosure and a sensible margin around it, taken up beyond the shower head and returned onto the floor so there is no break in the waterproof layer. In an open wet room the treated area is larger because water travels further across the floor.
Why do corners and the drain matter most?
Failures nearly always start at junctions rather than in the middle of a flat wall. Internal corners move slightly, and the drain is where water concentrates, so those points get reinforcing tape, collars and extra attention rather than just another coat of liquid membrane.
What about the fall to the drain?
A wet room floor must slope towards the drain so water leaves the room instead of sitting on the tile. That fall is usually created by a former or a screed and needs to be set before tiling, because it cannot be corrected with adhesive afterwards.
Does TLS Tiling install the tray, drain or plumbing?
No. We are a tiling-only specialist: we do not fit trays, drains, sanitaryware or do plumbing and electrics. We tank and tile onto a correctly installed substrate, and we are happy to coordinate with your plumber so the stages happen in the right order.
How do I know a wet room has been tanked properly?
Ask which membrane system was used and see it before the tiles go on — a tanked wall is obvious at that stage, usually as a coloured membrane with taped corners. Once tiled, it is hidden, so photographs taken during the work are the honest record. We take them as a matter of course.
How TLS Tiling can help
We tank and tile wet rooms and shower areas across London and around twenty miles out, with over ten years' experience and an NVQ in tiling. You supply the tiles, we handle preparation, waterproofing and tiling — send photos for a free quote.
Related services: Wet rooms & waterproofing, Bathroom tiling, Floor tiling.