A wet room is not a tiled room with a drain — it is a deliberately sealed box that happens to have tiles on the inside. Water finds the weakest seam, so waterproofing is a system of layers, not a single product. Build the stack in the right order and it lasts decades.
The principle: one continuous tanking plane
Every surface — floor, walls, tray, niche — must belong to a single, unbroken waterproof membrane. Tiles and grout are wear surfaces, not the seal. If water gets past the tile, the membrane beneath is what saves the building.
Layer 1 — the substrate
- Sound, dry, flat, load-bearing. Fix movement first; no membrane hides a failing base.
- Rigid, not springy. A tile backer board on walls gives a stable, waterproof plane to tank onto.
- On the floor, a pre-sloped tray sets the fall; a decoupling membrane handles a cracked slab.
Layer 2 — the board system
Backer board is where walls become waterproof by manufacture. Screw it to the studs on the marked grid, leave a 2–3 mm gap at joints, and you have a continuous rigid plane ready to tank.
Layer 3 — the membrane and tanking
- Prime per the system's instructions.
- Apply liquid or sheet membrane to the whole wet area, carrying it 100 mm up the walls (or to splashing height).
- Bond the tray flange and niche into the wall membrane so seams are buried.
- Reinforce every corner and penetration with tape — internal corners leak first.
Layer 4 — joints and penetrations
| Junction | Treatment |
|---|---|
| Wall / floor | Continuous membrane, no break at the change of plane |
| Tray flange | Overlapped and sealed into wall membrane |
| Niche | Internal corners taped, shelf fallen slightly |
| Pipes / mixer | Sealed collar or grommet, then tiled around |
Layer 5 — tile and finishing
- Use a flexible, waterproof adhesive rated for wet areas.
- Butter the back of tiles fully; voids behind tile hold water.
- Grout is cosmetic — keep the membrane intact and the slope correct.
The mistakes that sink wet rooms
- Treating grout as waterproofing.
- Leaving a gap at the wall/floor change of plane.
- Skipping the flood test to save a day.
Frequently asked questions
Is tile and grout enough to waterproof?
No. Grout and tile are wear surfaces. The membrane beneath does the sealing; grout is cosmetic and slightly permeable.
How high should the membrane go up the wall?
At least 100 mm, or to the height water can splash. In a fully tiled wet room, tank the whole area for safety.
Do I need a flood test?
Strongly recommended. Flood the tray and floor for 24 hours before tiling to confirm the membrane holds.
Can I tank over old tile?
Yes, with a suitable primer and membrane, provided the existing tile is sound and well bonded.
Where do wet rooms actually leak?
Internal corners, tray flanges and pipe penetrations — every one needs taped, reinforced sealing.
Build the box, then tile it
TANYTE supplies the whole waterproof stack — backer board, shower tray, niche and membrane — as one compatible system.