When we think of Sauna, we generally think of a wood-lined room heated by an electric or wood-fired kiuas (even though my last post was on the discovery of an old smooth plastered sauna.) The wood is integral to the experience—for the aesthetics of its look, its pleasant smell, and ability to take the humidity and temperature extremes. But all wood is not alike, and the question of what kind of wood to use always arises. The answer to that question, like everything else these days, is changing.
Typically in the US, especially in the generic gym and hotel saunas, and home kit saunas, Western Red Cedar is used. As its name implies, it is from the western US and Canada. All lumber is graded and each board is stamped as it runs through the mill. The grade indicates species, appearance, mill, and strength of the wood. The letters A-D are modified by Select, Clear and STK (select tight knots). For cedar saunas, it will be either a clear select grade or STK, the latter being almost half the price of the former. Cedar is also produced mainly for exterior siding applications and comes with a textured surface on one side that, unlike the sawing pattern of rough sawn lumber, is applied in the mill after sawing. This rough surface is considered the “good” side to which the grade applies. A big frustration with cedar is that I want the smooth side facing out and, since the board is graded to the other side, there is no guarantee that the smooth side has the appearance that the grade indicates.
Color in cedar varies a lot: one side can be red and the other have annoying stripes of white wood. Clear select grade A boards will be better, but they come at a premium price, currently about $12-15 a board foot (12’x1 ft x1” thick, nominal dimensions). For years I have typically used Western Red STK for the walls and maybe Clear Select grade on the benches. This wood comes from either Idaho or British Columbia (BC). STK is likely from managed (regenerated) forest plantations and Clear Select is from larger old growth trees in BC. There is a guilt factor here I consider, so I veer towards STK whenever possible. (I also use Northern White Cedar frequently in freestanding saunas and our mobile saunas but that is the topic of another post.)
Cedar has been touted for its stability in the heat—which is true, and because of its low density, it doesn’t get hot to the touch—an important feature in a hot room with bare flesh touching the walls and benches.
Wood is a global commodity affected by the stock markets, inflation, building trends, shipping woes, fire seasons and the whims of political leaders who set tariffs as a way to taunt each other. You can make a career (and people do) out of studying the ebb and flow of lumber supply and prices. Add to this mix the pandemic and you have a roller coaster of unpredictability. The information I gleaned from building ten or twenty years ago I can no longer rely on. Suppliers have come and gone, quality has gone down and prices go mostly up.
The Pandemic created a real change in the labor force as well. There was never a shortage of raw lumber-logs but as workers and truck drivers got sick or just quit, mills shut down and logs piled up. The calculus used to predict building trends was skewed by everyone staying home and building decks with their pandemic relief money and we all saw prices soar while availability of lumber, especially cedar, shrank. In the meantime, the cedar I could get has been showing up with major defects, some from the mill, some from very poor handing: fork lift stabs are so common I have to over-order for very job. I assume this is the result of experienced older workers leaving the work force and being replaced by a cohort too inexperience to understand that the 6-board bundle they just mangled cost me more than what they make in two days. Some days I feel like all I make is very expensive kindling.
The truth is, in Finland, the source of my sauna inspiration, they don’t even have Western Red Cedar. They have soft wood species similar to what we have—spruce, pine, fir (SPF) but, in general, the quality and nature of wood varies by region. Wood from northern climates grows slower and has a denser grain.
As in Scandinavia, trees in uniformly dense forests have straighter grain as the trees race to reach up for the sun. Compare a “lone wolf” white oak, with its sprawling branches, to a deep forest oak.
Norway Spruce is the wood choice for many Finns, as are Alder and Aspen, which are soft hardwoods. The latter grow bigger there than our typical Aspen and Alder which rarely found at local mills. Cedar has been touted for its stability in the heat—because of its low density, it doesn’t get hot to the touch. But now Scandinavians have started using a thermal process of using heat and steam to modify wood and make it more stable and rot resistant (or so the web pages claim). I suspect there is also a Scandinavian work ethic at play: working in the trades there does not carry the same stigma as being a high school dropout, as it does here, and attention to detail and quality are paramount. Call it the IKEA effect.
Thermory and Lunawood are two brands available now in the US. The shipping crisis (highlighted by a boat getting stuck sidewise in the Suez Canal) has calmed down so now the economy of having quality wood freighted in containers from the Baltic’s to you (via a US distributor) probably makes more sense than wasting your time perusing the aisles of a big box store (or several) to glean out a few good cedar boards from a pile of fork lift-stabbed firewood. I also measure the time I spend trying to hide defects as I install the wood. While I still want to get all of my materials as locally sourced as possible, we are now in a global economy and looking abroad is certainly starting to make more sense to me. —Rob
wood using heat and steam
