Saunas can be made from a wide variety of woods and have frequently been made from whatever was most readily available locally. Woods that warp, splinter or absorb moisture will need to be replaced much more often, however, and may make for uncomfortable sauna benches.
Cedar is a popular choice for sauna construction; it has a pleasant aroma, stays cool to the touch when the sauna heats up and contains natural oils that allow it to resist moisture. White aspen and poplar, however, are both nonallergenic and are better choices for those who are allergic to the oils in cedar as well as those who simply dislike the odor. Other viable sauna woods include balsam fir, white fir, eastern white pine, bald cypress, sassafras and Douglas fir.
Barking Up the Wrong Tree
Avoid building a sauna out of woods known to expand significantly when exposed to water and moisture as well as those likely to feel uncomfortably hot as the sauna temperature rises. Oak, hickory, magnolia, birch, elm, sweet gum and sycamore are poor choices for sauna construction.