A hammam is a stone room, not a steam box

The göbek taşı and the heat under it

The navel stone is a raised marble slab heated from below by a water loop or electric mat set in the screed. It runs at 40-45 °C on the surface — warm enough to relax muscle through your back over twenty minutes, not hot enough to burn. Getting that even is the craft: the loop spacing tightens at the edges because the perimeter loses heat to the room.

Around it the room is warm and humid rather than hot: 40-50 °C air, high humidity, no scalding. That is why a hammam suits a Rwandan hotel spa where guests may sit for an hour, and why families use it where they would not use a 90 °C sauna.

Tadelakt, marble and what survives here

Tadelakt — lime plaster polished with olive-oil soap — is the traditional wall finish and it is genuinely waterproof when it is done properly, which means by hand, in several passes, by someone who has done it before. It gives the soft ochre glow you cannot get from tile.

Marble is the other route: cooler to the eye, heavier on the structure, and easier to maintain. For the floor we use honed rather than polished stone, because polished marble plus water plus bare feet is how people fall over.

Domes, light and brass

A pierced dome throws the traditional points of daylight across the steam. On a Kigali villa we usually build it as a shallow dome with fibre-optic lights instead of roof penetrations — the two rainy seasons are unforgiving to holes in a roof, however beautiful they are in Istanbul.

Fittings are brass because it patinates instead of pitting. Chrome in a hammam looks tired in three years.

In short

• Heated göbek taşı at 40–45 °C, loop spacing tightened at the perimeter
• Hand-applied tadelakt or honed marble — never polished stone on a wet floor
• Shallow dome with fibre optics instead of roof penetrations, because of the rains
• Brass fittings throughout: it patinates, chrome pits