Sauna or steam room? The one-line difference that decides your BOQ

Two rooms, one word

A Finnish-style dry sauna is a timber cabin heated by a stove of stones to 90-110 °C, with low humidity and a ladle of water thrown on the stones for a short burst of steam when the bather wants it. A steam room is a tiled or solid-surface room filled with steam from a generator, run far cooler: Harvia, the Finnish heater maker, gives 45 to 50 °C as the ideal temperature for one. In India the word sauna is used for both, so a line that reads sauna for 6 persons, complete can be answered with two completely different rooms. We build the first. We do not build steam rooms, hammams or salt rooms.

What differs, line by line

How the mix-up shows up in a tender

Two bidders read the same line. One, a steam-equipment supplier, prices a generator, tiling, a drain and a sloped ceiling. The other, a timber supplier, prices a cabin and a heater. Their numbers differ by a wide margin and neither is wrong. The comparison sheet then rewards the cheaper reading, the consultant discovers the mismatch at design review, and the programme loses the weeks that the correction takes. The fix costs one sentence at the start.

Words that fix the line

For a dry sauna, write:

• Dry sauna cabin, Finnish type, seats and cabin dimensions stated, working temperature 90-110 °C, low humidity.
• Electric heater with stones, rated power in kW and the supply it needs, mounted behind a timber guard.
• Thermally modified timber or cedar cladding and benches, insulated shell, vapour barrier, air inlet and exhaust.
• Glass front or glass walls as drawn; door opening outwards; indirect lighting; control panel outside the cabin.

For a steam room, a different set applies, and it is a different trade:

• Steam room, working temperature about 45-50 °C, steam generator with its rating and water supply.
• Waterproofed shell, tile or solid-surface finish, sloped ceiling, floor drain and extract.

Infrared cabins are a third thing

An infrared cabin heats the bather directly with radiant panels, not the air with a stove. It appears next to sauna heaters in the same item of the BIS order described in the paperwork note, which is a reason to name it separately in a BOQ. It is not in our range for India.

The heater, the supply and the mains

Small cabin heaters run on a single-phase supply; larger ones, from about 8 kW, need three phases, and a manufacturer such as Harvia lists a 400 V 3N~ electrical group for its larger heaters. On the mains, BIS standard IS 12360 gives 50 Hz as the frequency and lists 230 V single-phase and 230/400 V three-phase as preferred values; BIS has kept the changeover from 240/415 V in abeyance since 2011, so an existing supply may still be 240/415 V. Confirm the supply with your utility and put the figure in the BOQ.

Which one do you need?

What a consultant checks at design review

• That the BOQ line names the room: dry sauna or steam room, with the working temperature.
• That the heater's rating and supply appear on the electrical schedule, and a feeder and DB way are reserved.
• That the cabin's exhaust has a route out of an air-conditioned room, and that the route is drawn.
• That a floor drain exists only where the room needs one: a steam room does; a dry sauna does not.
• That finishes suit the room: timber inside a dry sauna, tile or solid surface in a steam room.
• That the door, the glass and the lighting match the room's heat and are rated for it.

Five assumptions to test, and what is wrong with them

1. A sauna needs a drain. A dry sauna does not; a steam room does.
2. Tile is fine in a sauna. At 90-110 °C, tile and grout are the wrong material; the bench would be too hot to sit on.
3. One room can be both. A cabin that tries to be both is a poor example of each.
4. More steam is more sauna. A dry sauna is judged by its heat and its air, not by its fog.
5. The heater and the generator are interchangeable. They are different machines with different supplies, water connections and maintenance.