Steam rooms built wet-proof from the slab up

The tank under the tiles

We build the room as a sealed tank: liquid membrane over the slab and up the walls past the ceiling junction, reinforcing tape at every corner and change of plane, then screed to a fall of at least 1:50 towards the drain, then tile. Steam condenses on every surface and runs down. If there is a flat spot, water sits there, and within a year it is behind the tiles.

The ceiling gets a fall too — between 3 and 5 degrees — so condensate runs to the walls instead of dripping on the person below. That single detail separates a steam room people use from one they complain about.

Sizing the generator

Generator output is calculated on room volume with a correction for the surface materials: porcelain and glass mosaic need less than natural stone, which is thermally heavy and soaks up the first ten minutes of every session. A dark basalt bench looks superb and costs you generator capacity — we price both options rather than quietly picking the cheap one.

The generator lives outside the wet room, within about 10 m of it, somewhere serviceable. In a Kigali villa that is usually a plant cupboard or the back of a garage.

Ventilation and the bit people forget

A steam room needs an extract that runs after the session, not during it. We wire a run-on timer so the room dries out overnight. Without it, you get the smell — and the smell is the beginning of the mould.

In short

• Liquid waterproof membrane over slab, walls and ceiling junction, taped at every corner
• Floor falls 1:50 to the drain, ceiling pitched 3–5° so condensate runs to the walls
• Generator sized on volume with a correction for stone versus porcelain finishes
• Run-on extract timer so the room dries overnight