Starlight Steam Room

Scope of work

A single room, built to a high finish standard: a sealed steam enclosure with mouldedseating, a fibre-optic ceiling that reads as a night sky through the vapour, and the generator, controls and drainage that make it work. The package covered the room build-upand tanking, the finishes, the seat geometry, the generator and steam head, the lighting installation and commissioning.

Sizing the generator

Steam generators are sized on enclosure volume and on how much heat the room loses through its surfaces — and those two are not proportional. A room lined in mosaic on a masonry backingloses far more than the same volume over insulated board, because the finish is a large thermal mass that must reach temperature before the room holds steam. General practice is to calculate the volume, apply a correction for the finish and for glazing, then add headroom for dooropenings. Undersizing shows up as a room that collapses when someone walks in; oversizing as scalding bursts and a short-cycling generator. Ourhow to build a steam room guide and steam and sauna supplier page set out the same method.

Seat geometry, steam head and the ceiling

Comfort in a steam room is mostly geometry. Seats are moulded with a fall so water runs off rather than pooling under the bather, backs are raked, and the front edge is radiused becausea square edge in a wet room is unpleasant against the back of the knee. The steam head is placed low, away from the seats and never where a bather could reach or brush against it, withthe discharge directed into open floor. The ceiling is pitched or coved — even a modest fall is enough to move condensate to the perimeter instead of dropping it on the person below.That fall is also what makes a fibre-optic ceiling practical: the light points are set into a sealed lining, the emitters and their driver sit outside the wet envelope entirely, and only the fibres cross the boundary, so the enclosure stays sealed and nothing electrical lives inthe steam.

Tanking and drying down

A steam room is the hardest wet room in a building to waterproof, because it is loaded with vapour rather than splashed: pressure drives moisture into every joint and penetration. Theroom is fully tanked before finishes — bonded membrane over screed, walls and ceiling,reinforcing tape into every corner, movement joint and penetration, dressed into the gully.Epoxy grout throughout, falls in the screed. And it needs extract that keeps running after the session, because a steam room sealed up wet has a short life. Product detail on oursteam room andsteam room design pages.

What we solved on site

The starlight ceiling and the waterproofing are in direct conflict: one wants hundreds of small penetrations in the lining, the other wants no penetrations at all. The resolution wasto build the ceiling as a sealed panel, complete with its fibres, before it went into theroom, so that the membrane was breached in a controlled way on a bench rather than overhead in a finished enclosure — and to keep every electrical component, including the light source,outside the steam envelope with only the passive fibres crossing it. That also means the emitter can be serviced without opening the room. Related reading:private spa andour United States page.

Frequently asked questions