Sauna Ledger

How to Choose an Outdoor Sauna

Choose an outdoor sauna by working back from your yard, your panel, and the room volume your heater can warm. Use this order and checklist.

Start with the heater and the room volume

Heater capacity is tied to room volume, so size the room and heater together. Harvia, a heater maker, suggests roughly 1 kW of heater power for each cubic meter of room, with extra capacity for glass, bare stone, or uninsulated log walls (Harvia support). One cubic meter is about 35 cubic feet.

Makers publish a volume range for each heater. One 6 kW, 240 V heater lists 169 to 300 cubic feet (Harvia Kip60B). An 8 kW unit lists 251 to 424 cubic feet (Harvia Kip80B).

Both errors cost you. Harvia says a heater that is too small takes too long and wears out faster. One that is too large heats the room quickly but does not give the stones time to store heat for steam (Harvia energy FAQ). Harvia also says outdoor saunas and cold climates need a higher-capacity heater to offset heat loss (Harvia wood-burning guide).

To get your room volume, multiply length, width, and height. Both listed heaters above need a room at least 6.56 feet tall.

Seats and size

Count the people who will sit at once, then check the volume. Make the bench layout first, then multiply out the volume and compare it with the heater's range. If the volume lands outside every range you can power, change the room, not the numbers.

Bench seating takes floor area that does not add much volume. A small, tall room can hit the same volume as a larger low one, so look at the layout and not just the cubic feet.

Shape

The two common shapes are a rectangular cabin and a barrel. Our barrel vs. cabin guide covers the trade-offs in detail. The short version: compare volume, not outer dimensions, because a round cross-section and a flat-walled box of the same length and width hold different amounts of air.

Wood

Outdoor walls see rain, sun, and cold, so decay resistance matters. Western red cedar and northern white cedar are both rated durable to very durable against decay, while western hemlock and aspen are rated non-durable (Wood Database: western red cedar, northern white cedar, western hemlock, quaking aspen). Our wood types guide compares all the common choices.

Heater type

Site prep

Choose a level spot that does not collect water. A guide from This Old House says to keep a shed-type structure at least 3 feet from fences or other structures, and to call 811 before you dig (This Old House). That is a general shed guideline, not a sauna rule. Your local setbacks may be larger. See the foundation and electrical guide.

If you live in snow country, look up the ground snow load for your address. One Colorado county tells permit applicants to start at the ASCE Hazard Tool (Elbert County, CO instructions).

Rules to check before you buy

  1. Building permit. One city exempts one-story detached structures used as sheds and playhouses up to 120 square feet from a building permit, but says the exemption does not allow work that breaks the code (City of Beaumont, CA). Your city may differ, and a sauna is not clearly a shed. Ask.
  2. Electrical permit. The same list exempts only minor electrical work, such as replacing a breaker with the same rating. A new 240 V circuit is not on it.
  3. HOA. An HOA's approval comes first and is separate from city permits, and unapproved structures can lead to fines or removal at your expense (FirstService Residential). Read your covenants first.

Budget factors

We do not quote prices here. These are the items that move the total:

Checklist

Sources

More guides