Canadian hemlock for saunas: a pale, almost scent-free timber

The short answer

• Hemlock is the timber we use when a client wants a quieter room than cedar gives. It is pale, even and almost scent-free.
• It is excellent on walls and ceilings. Klafs, the German sauna maker, offers hemlock panelling in its Premium sauna.
• It is denser than cedar and moves noticeably more with changes in moisture, so drying, grade and installation matter more.
• It is not termite-resistant under Australian ratings, unlike western red cedar.
• Specify the botanical name and a clear grade. “Canadian hemlock” can mean two different species.

Our guide to choosing sauna timber explains how hemlock fits among the other options.

What it is and where it comes from

The hemlock sold for saunas from British Columbia is normally western hemlock, Tsuga heterophylla, which grows in coastal BC and the province’s interior wet belt. The trade name “Canadian hemlock” is less precise: some suppliers, including Thermory, use it for eastern hemlock, T. canadensis. In construction grades, western hemlock is often sold mixed with amabilis fir as “hem-fir”, which is not what you want in a sauna. Ask for the species and grade in writing.

Appearance and grain

Hemlock is pale: WoodSolutions describes it as pale cream with few knots, sometimes with a lavender cast, and other references describe a pale brown with a purplish tinge. The grain is straight. The texture is coarser and less even than cedar’s, because the soft earlywood and harder latewood alternate in each growth ring.

The result is a calmer room than cedar gives. Where cedar ranges from pink to chocolate across a single wall, hemlock reads as one soft, light tone. That suits minimalist interiors and clients who find cedar’s colour variation busy.

Clear grades

SAWO describes its sauna hemlock as typically knot-free, and Finlandia, a US sauna manufacturer, specifies clear western hemlock. Knot-free status is a grade, though, not something the species guarantees. Clear boards matter most wherever skin touches, because knots are denser than the surrounding wood and pass heat faster. Put “clear” on the order, alongside the botanical name.

Aroma

Hemlock has no characteristic scent. That is its main appeal: the room smells of warm timber, the löyly and little else. It suits people who are sensitive to strong smells, and anyone who has tried a cedar sauna and found the aroma too much.

Resin

Hemlock is non-resinous, so there is no resin to soften or bleed at sauna temperatures. That puts it ahead of untreated pine and spruce, and level with cedar on this point.

How it feels to touch

Hemlock is a little denser than cedar, and published figures vary:

The US Forest Products Laboratory gives western hemlock a thermal conductivity of about 0.14 W/m·K at 12% moisture content (0.12 for eastern hemlock), against about 0.10 for western red cedar. In practice a hemlock wall feels no different from any other timber wall, because you rarely touch it. On a bench the difference is noticeable to some people: clear hemlock is comfortable, but a lower-density timber is gentler.

Stability and moisture movement

This is where hemlock asks more of the installer. Western hemlock’s volumetric shrinkage from green to oven-dry is 12.4% in the Forest Products Laboratory’s figures, nearly double cedar’s 6.8% (eastern hemlock is 9.7%). Some sauna suppliers say hemlock “doesn’t warp” in saunas. That is plausible for well-dried, clear stock, but it is a marketing claim rather than a property of the species.

What keeps a hemlock room tight:

• Kiln-dried stock at a low moisture content. Finlandia specifies no more than 11% for wall and ceiling boards.
• Acclimatisation on site after wet trades are finished, before the boards are fixed.
• Battens and an air gap behind the lining, so both faces of the board dry evenly.
• Good ventilation and drying after use, which matters in south-east Queensland’s humid summers.

Durability and termites

WoodSolutions rates western hemlock:

• Durability Class 4 above ground and in ground, the lowest Australian class.
• Not resistant to termites.
• Not susceptible to lyctid borers.

Inside a heated, ventilated hot room, low decay durability is rarely a problem, because decay needs timber that stays wet. Termites are the bigger consideration in Queensland, where drywood termites need no contact with the ground. Hemlock is best kept to the interior lining of a well-built room. On an outdoor sauna, cladding and structure call for a different approach, and termite management is a matter for the builder and certifier.

Where it works in the room

• Walls and ceilings: its strongest use. Klafs offers spruce or hemlock panelling in its Premium sauna, with obeche (abachi) headrests and backrests as standard, and its untreated spruce and hemlock element saunas carry Germany’s Blue Angel eco-label.
• Benches and backrests: acceptable in clear grade, and SAWO offers hemlock bench timbers. Where the lightest feel matters, a lower-density timber such as clear western red cedar is usually the better choice wherever people sit and lean.
• Commercial rooms: hemlock linings suit commercial saunas, and its neutral scent is an advantage in a room shared by many people. Pair it with benches chosen for wear.

Ageing and care

Like every sauna timber, hemlock darkens with heat, light and use, faster where steam hits. On a pale timber, sweat and water marks on benches show sooner, so towels and drying the room after each session matter more than in a darker room.

Care follows the same rules as any hot room:

• No varnish, lacquer, paint or stain on interior surfaces. Harvia, Finlandia and Tylö-Helo all say so.
• Walls can stay unfinished. Harvia says a family sauna’s walls need no treatment.
• Bench oil or wax, not both. Tikkurila makes its sauna paraffin oil for benches only, and says its sauna wax should not go over oiled timber. Oil deepens colour, which is more visible on a pale timber, so test it on the underside first.
• Light sanding along the grain removes most marks.

See our care guide for cleaning routines.

Hemlock and cedar compared

Choose cedar for its stability, comfort on benches and durability. Choose hemlock for a calm, near-neutral room. One established approach is hemlock walls and ceilings with benches in a lighter timber. Our western red cedar guide covers cedar in detail, and thermally modified timber is a third option, with a darker look.

Advantages and disadvantages

Sourcing

Western hemlock is listed as Least Concern by the IUCN, and Canadian hemlock is stocked by Australian sauna timber suppliers. As with any species, request FSC or PEFC chain-of-custody documents for the specific order if certification matters to the project.