Pick the type
| Type | Good at | Watch out for |
|---|---|---|
| Insulated cabin | lowest running cost, room for a changing area, big windows possible | needs a proper frame, insulation and vapour barrier |
| Barrel sauna | compact, quick to assemble, classic look | solid 40–45 mm wood walls lose more heat than insulated ones; the steel bands need re-tightening as the wood dries and swells |
| Cube with a glass front | the view | glass loses heat fast: a glass front can need a heater one or two sizes up |
| Log sauna | thick solid walls, traditional feel | slow to heat: the logs soak up heat, so heater makers count the room as 1.5 × its volume |
You can try each type at your own size in the 3D studio, with the heat-up time and running cost updating as you change it.
Size
- Inside height about 2.0–2.2 m, so the upper bench can sit about 1.0–1.2 m below the ceiling (see bench height).
- Seats: allow about 60 cm of bench per person sitting, and about 1.8–2.0 m of bench length to lie down.
- Keep the hot room compact. Every cubic metre has to be heated. A small changing room in front of the hot room keeps cold air out when the door opens and gives you a dry place for towels.
The sauna size calculator turns the number of people into inside dimensions.
Heat-up and running cost in cold weather
Outdoors the walls lose heat to cold air and wind, so the same sauna takes longer and uses more energy in winter. The table is our heat model for an insulated garden cabin at different outside temperatures, with the electricity price for your country.
| Outside | Heat-up time | Energy per session | Cost per session |
|---|---|---|---|
| 68 °F | 30–45 min | 8.2 kWh | $1.51 |
| 50 °F | 40–55 min | 10 kWh | $1.82 |
| 32 °F | 45–60 min | 11.7 kWh | $2.14 |
| 14 °F | 55–70 min | 13.3 kWh | $2.43 |
| -4 °F | 60–85 min | 15 kWh | $2.74 |
Heat model: insulated garden cabin (100 mm mineral wool, glass door, flat roof), heated to 176 °F at the ceiling, then an hour of bathing. Heater: HUUM DROP 9. Electricity $0.18/kWh (United States average). Wind and a poorly sealed door add to the figures.
Well-sealed doors and a roof with a proper overhang matter as much as the insulation thickness: draughts and wet walls are what make outdoor saunas slow.
Foundation and floor
- Small saunas and barrels often stand on a level bed of compacted gravel with paving slabs, on concrete pier blocks or on ground screws.
- Cabins need a frame foundation (piers, screws or a concrete slab) that keeps the wood well off the ground with air moving underneath.
- The floor should drain: a tiled or sealed floor with a drain if you plan to shower inside, or slatted boards over a gravel bed in barrels.
- Distances: keep the sauna, and especially a wood stove and its chimney, as far from the house, trees and the boundary as local rules require.
Electric heater or wood stove
- Electric: a garden sauna needs its own supply cable from the house's fuse board, buried or protected as the local code requires and installed by a licensed electrician. Heaters from about 6 kW up are usually three-phase in continental Europe and 240 V in North America. The electrical requirements tool tells you what to ask for.
- Wood: no power line, but a chimney with the stated safety distances, a dry store for firewood, and in many places an approval of the flue before first use. See wood-burning sauna stoves.
- Either way, size the heater from the room's effective volume with the heater size calculator; outdoor saunas often have glass and solid wood walls that push the figure up.
Permits
Many countries let you build a small garden building without a permit below a certain floor area or height, but the limits differ by country and often by municipality, and wood stoves often need a chimney inspection. Check with your local building authority before you order a kit.
Weatherproofing
- A roof with an overhang, and a membrane, shingles or a metal roof over a barrel's staves, keeps rain and sun off the wood.
- Treat the outside with an exterior wood oil or stain; never treat the inside of the hot room.
- Fit door seals, and plan for snow load on the roof where you live.