Steam rooms in indigo mosaic

The tank

Liquid membrane over the slab and up the walls past the ceiling junction, taped and detailed at every corner, screed falling at least 1:50 to the drain, then mosaic or terrazzo. The ceiling pitched three to five degrees or gently domed so condensate runs to the walls rather than onto people.

Where a room is built into an existing block wall — which here it usually is — the membrane is detailed into it properly rather than stopped short and hoped over.

Humidistat, not a timer

Mechanical extract ducted to outside, sized for several air changes after a session, controlled by a humidistat. In Lagos a timer cannot know how wet the outside air is on a given afternoon, and a fan that stops with the room still wet is how a steam room starts growing things.

Extract terminating in a ceiling void is not ventilation. We find it regularly in other people's work and it is the most damaging shortcut in this trade.

Water, and the generator that has to live with it

Supply here is often borehole, and borehole chemistry varies enormously between Lekki, Ikoyi and the mainland. We test at the property before specifying, because the descaling interval follows from the result.

A steam generator is also a substantial electrical load with a duty cycle, so it gets the same circuit conversation as a sauna heater rather than being connected wherever is convenient.

In short

• Continuous membrane detailed into existing blockwork
• Humidistat extract ducted outside — never into a ceiling void
• Borehole water tested at the property before the generator is specified
• Generator load placed on the right circuit, like every other appliance