Building a Cordwood Masonry Sauna

A MOTHER reader describes building a cordwood masonry sauna from scratch, includes information on installing sauna doors, windows and rafters, mortar mix, types of woods to use for the sauna and building diagrams.

| December 1999/January 2000


The earth roof in snow.


Learn about building a cordwood masonry sauna from the ground up. 

While the idea of an electric sauna, particularly a redwood electric sauna, makes me cringe today for environmental reasons, I didn't know any better at age 16. And I accepted the American line of thought that sauna was only properly experienced in a bone-dry atmosphere. The idea was that high temperatures could only be endured at low humidity, a myth still unfortunately accepted by many Americans and touted at too many hotels. Sauna, I was taught early on, was meant to be a dry experience, save for the moisture produced by one's own sweat glands.

My first clue that I was on the wrong track came three years later at a hotel in Iceland, where the sauna was kept at an unbelievable 220 degrees Fahrenheit (water boils at 212 degrees Fahrenheit) and the Icelanders would occasionally throw water on the hot basalt rocks that covered the stone, thus creating lowly (pronounced "slow-lu"), the "sacred steam" so important to true sauna. I knew that sauna had Scandinavian or Norse origins, so I figured the Icelandic experience was a lot closer to sauna's roots than what I'd known in Massachusetts. In Iceland I learned that sauna — the authentic Finnish version of sauna — is not simply a sweat in a dry room. Sauna is an experience of contrasts, of wet and dry, great heat and cold. After a few minutes at 220 degrees Fahrenheit, some of the bathers would lower themselves into a pool of 45 degrees Fahrenheit water, the ultimate temperature and moisture contrast. While sauna has evolved over the past millennium (the introduction of the chimney in the 19th century was a particularly useful innovation), the basic characteristics that we look for in a good sauna building have remained the same.

A good sauna building is "seasoned" with several hours of high heat prior to use. While there are electric- and sometimes gas-fired sauna stoves, even in Finland, old-timers will tell you that the only authentic sauna is wood-fired. The Finns value the background aroma of wood and smoke, though no actual smoke remains in the stove room. There is practical sense to the wood-fired sauna, as well. In Finland, most country saunas are some distance from the home, with no easy access to electric wires or gas lines.

Centuries ago, the original saunas were earth-sheltered or of log construction, with both styles having plenty of thermal mass to absorb and store heat. Over the past 20 years, my wife, Jaki, and I have found an alternative to horizontal log construction: cordwood masonry. My article in the May 1995, MOTHER EARTH NEWS ( "Rob Roy's Earthwood Home") tells how we built our round two-story cordwood masonry earth-sheltered home, which also serves as the main campus building at our Earthwood Building School.

The "5-E" advantages that make cordwood masonry perfect for house building also make it ideal for building a cordwood masonry sauna: 1) ease of construction, 2) economy, 3) esthetics, 4) ecological harmony and 5) energy efficiency.

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