The Wood-Fired Sauna

Kinds of sauna

¹

Löyly is the steam that rises when water is thrown on the hot stones ¹. Temperatures run 80-110 °C (176-230 °F), usually 80-90 °C ¹. Finnish sauna culture has been on UNESCO’s intangible cultural heritage list since 2020 ¹.

Saunas in Wisconsin

Finnish immigrants settled northern Wisconsin from the 1890s, bringing the sauna with them ². The legend is that homesteaders built the sauna before the house - less a matter of priorities than practicality, since it was a small building with a hearth that a family could live in while building the house ². Palmquist Farm in Brantwood still keeps a chimneyless smoke sauna ². Lakeshore saunas remain common across the Northwoods.

Building one

Size and layout:

• A small sauna can be 6 × 8 feet inside, with a changing room in front.
• Benches high - the upper bench about 3.5-4 feet off the floor - because heat stratifies; feet should be above the stove’s top.
• Low door that opens outward, with no lock; a small window for light.

Structure: log walls (see the log building lessons) or a timber or stud frame, insulated and lined with clear, knot-free softwood - aspen, spruce, cedar, or basswood - that stays cool to the touch. Avoid resinous knots and finishes on interior surfaces. Benches from aspen or basswood, fastened from below so no nails touch skin.

Stove and stones:

• A purpose-built sauna stove with a deep stone basket; use igneous stones (peridotite, basalt) meant for saunas - river rock can crack or burst.
• A heat shield and the stove maker’s listed clearances to combustibles, a non-combustible floor pad, and a proper insulated chimney through the roof.
• Feed the stove from inside or from the changing room through the wall.

Ventilation: a low fresh-air inlet near the stove and an outlet high on the opposite wall bring in oxygen and keep the air fresh (and carbon monoxide out). Install a CO detector in the changing room.

Foundations: a sauna is usually an unheated outbuilding between uses, so piers or a gravel pad with sills off the ground work well (see Stone Foundations), with the floor draining toward the door or a drain.

Local building and zoning rules apply to stove installation and outbuildings; check with your town or county.

What to take from this

Saunas come as chimneyless smoke saunas, wood-stove saunas, and electric ones; löyly is the steam from water on the kiuas stones, at usually 80-90 °C. Finns in northern Wisconsin built saunas first as a heated place to live while building the house. Build one with high benches, a low outward-opening door, clear softwood lining, a proper sauna stove with listed clearances and real sauna stones, a low inlet and high outlet for air, and a CO detector.