The Cordwood Sauna

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You might have noted that I've called for a 2 1/2" mud joint, a 2 1/2" sawdust insulation layer, and another 21/2" mud joint, or 7 1/2" in all. But the log ends are 8" long. The other 1/2" is divided equally between a recessed inner and outer mortar joint, further refined during the pointing process.

Pointing - sometimes called tuck pointing or grouting - is a very important step and should not be left out. With a stainless-steel knife, which has had the last inch of its blade bent up at a slight angle (say, 10°), press firmly on the mortar to smooth the mud. This accomplishes four things: l) It makes the wall look good. 2 ) It smooths the wall, creating a water-repelling instead of a water-absorbing surface. 3) It maximizes the friction bond between mud and wood, making the wall stronger. 4 ) The 1/4" recessed pointing provides a space in which repairs can be made, in case the wood or the mortar shrink. Log Jam® or Perma Chink®) flexible log chinking products are both suitable caulkings for the purpose, but are best applied if a 1/4" deep recessed mortar joint guides the smoothening brush between the log ends.

That's basically it: mud, sawdust, log ends, pointing. Follow this order and the wall practically builds itself. Logs can either be split or left in the round, and any size from 2" to 10" in diameter. Try to se lect log ends so that a constant 1"-thick mortar joint is left all around for ease of pointing.

Don't let logs touch each other. For a more thorough discussion of cordwood masonry, see my Complete Book ofCordwood Masonry Housebuilding (Sterling, 1992), The Sauna (Chelsea Green, 1996) or my video, Basic Cordwood Masonry Techniques. All are available from MOTHER'S Bookshelf.

Doors, Windows, Rafters

The sauna door frame is installed first, before cordwood work commences, so that the masonry can be laid up against the frame. Use heavy framing stock, such as 4 x 8 rough-rut lumber from a local sawmill. Make window frames ahead of time to fit your windows, which can be fixed (non-opening) thermal pane units. I have had good success over the years finding these windows in the back rooms of insulated glass manufacturers. Often I can buy small thermal panes for $10 or less. For a small, round sauna, the width of the window should not exceed 18 inches. The height is more flexible. Our two little windows are 18"-square and quite adequate. We also put a 12" x 24" pane in the door, so daytime light is good. A single 12-volt, 15-watt incandes cent electric light provides plenty of light for nighttime in the small 8', 8" internal diameter) stove room. ( Earthwood is off the grid.)

Although good sauna doors are available commercially, I always make my own for economy. I sandwich 2" of extruded polystyrene insulation between layers of rough-cut one-by planking. The planking and Styrofoam® is framed with 2 x 6s ( see illustration ). For the Earthwood sauna, I used 2 x 4s for the framing material and went with a 12"-wide window. The door window is optional, particularly if you have another source of natural light.

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