A home steam room is the most demanding heat installation a house can take, because unlike a sauna it puts saturated moisture into a sealed enclosure every time it runs. Done properly it is excellent. Done as a tiled shower with a generator bolted on, it is a maintenance problem that will outlast your enthusiasm.
The enclosure is the project
Everything begins with an enclosure that can be sealed: a waterproofed substrate behind the tile rather than tile alone, a vapour tight door including the top, and continuous sealing at every penetration for lights, the steam head and the controls. Steam finds gaps that water never would, and a gap means moisture inside a wall.
Ceiling fall and condensate
A flat ceiling in a steam room rains on you. The ceiling needs a fall of a couple of degrees toward a wall so condensate runs down rather than dripping, and the finish should be a material that sheds it. This is the detail most often skipped in a conversion and the one occupants complain about first.
The generator and its service access
Generators are sized to enclosure volume, adjusted up for stone, glass and exterior walls. They go outside the wet area, within the maker's pipe run, somewhere that stays above freezing and where you can reach them: they need periodic flushing for scale, and a unit buried behind finished tile is a unit nobody maintains.
Against a sauna, honestly
A sauna needs a dry enclosure, a circuit and clearances. A steam room needs all that plus tanking, drainage, a sloped ceiling and glass. The hardware costs are comparable and the building work is not. If you are not already opening up a bathroom, the sauna is the cheaper and lower risk way to get heat at home.
Questions people ask about home steam room
Can I convert an existing shower?
Only if the enclosure can be made vapour tight and the ceiling given a fall. An open topped shower cannot hold steam.
Where does the generator go?
Outside the wet area, within the maker's pipe distance, frost free and reachable for flushing. Access matters as much as distance.
Does a steam room cause mold?
Only if it cannot dry. With proper waterproofing, a sloped ceiling and ventilation between sessions it is manageable. Without them it is likely.