Steam rooms in green mosaic and honed granite

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 stone. The ceiling pitched three to five degrees or gently domed so condensate runs to the walls instead of onto people.

Where a room backs onto exposed granite — which here it often does — the membrane is detailed into the rock face 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. 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 single most damaging shortcut in this trade.

Water, tested at the property

Supply here varies between mains, borehole and rainwater harvesting, and often changes through the year. We test at the property before specifying the generator, because the descaling interval follows from the result and because a scaled generator on an island is a long wait.

In short

• Continuous membrane detailed into granite and blockwork alike
• Humidistat extract ducted outside — never into a ceiling void
• Water tested at the property, including rainwater and borehole
• Green glass mosaic and honed granite benches priced against porcelain honestly