Importance of Wood

The use of wood in saunas serves a functional purpose beyond mere aesthetics.

Wood's hygroscopic properties help to regulate temperature and humidity, creating a more comfortable environment.

Ideally, around 80% of the sauna's wall surface area should be covered with wood. It's preferable to use softer woods over harder ones, as they expand and contract more uniformly. However, if mixing different wood types for aesthetic reasons, it's essential to account for variations in expansion and contraction rates. It's best to avoid woods that become excessively hot to the touch in areas with frequent skin contact.

Heat-treated wood options like Thermory offer a viable alternative. While cedar is popular in the U.S., it's less commonly used in European countries like Finland and Sweden due to its strong fragrance, which some find overwhelming and irritating to the respiratory system or skin. Additionally, cedar's aroma may conflict with desired fragrances in the sauna experience.

The preference against cedar in Finland may also stem from its absence in the local environment. Some Finns and Swedes question the choice of using such a strongly scented wood in sauna construction.

For interior cladding, a nominal size of 1” x 4” (actual size 0.75” x 3.5”) is generally recommended. Wider or thinner boards may work in warmer climates or indoor settings but can warp in colder conditions. Consultation with a local woodworker familiar with the behavior of different woods in your climate can provide valuable insight.

Regarding interior cladding orientation, vertical placement can lead to moisture seepage between boards, potentially causing trapped moisture issues. However, with proper ventilation and an adequate air gap, this is typically manageable.

For indoor saunas, bare cement or tiled floors are suitable.

Exterior saunas benefit from a wood-framed floor and finish. Concrete or tile floors contribute to heat loss and increased temperature stratification, whereas a wood-framed floor can help maintain higher temperatures, particularly at the foot bench level.