The best wood for a sauna is a softwood that stays comfortable to touch when hot, holds up to repeated heating and moisture, and does not ooze resin. For an outdoor traditional sauna, cedar is the usual pick because it resists decay: Western red cedar is the richer, more aromatic option, and Eastern white cedar is lighter in color with tight knots. For an indoor infrared cabin, hemlock is the most common choice in our catalog because it is plain, even and has no strong smell. Spruce, aspen and thermally modified woods are also good choices, mostly for indoor rooms. Below we compare the species, grades and bench woods. For heater types, sizing and wiring, start with our home sauna buying guide.
What makes a good sauna wood
Sauna wood heats up, absorbs sweat and steam, then dries out, sometimes daily. Four properties matter most:
- Low density. All of the species below are light, soft woods.
- Decay resistance. This matters most on outdoor exteriors and much less inside a heated, vented room.
- Little or no resin. Pitch pockets can weep hot sap. Lunawood, a thermally modified wood maker, says in its sauna guide that its ThermoWood has no resin, “meaning there are no hot resin pockets.”
- Stability. Boards should not warp or gap as humidity swings.
Best wood for sauna use: species compared
Figures below come from The Wood Database species pages (average dried weight at 12% moisture and Janka hardness, the force needed to press a steel ball into the wood). Thermo aspen has no single published figure, so the row shows untreated quaking aspen.
| Wood | Dried weight | Janka hardness | Decay resistance | Scent | Typical use |
|---|---|---|---|---|---|
| Western red cedar | 23 lb/cu ft | 350 lbf | Durable to very durable | Strong, aromatic | Outdoor saunas, premium interiors |
| Eastern (northern) white cedar | 22 lb/cu ft | 320 lbf | Durable to very durable | Mild cedar scent | Outdoor barrels and cabins |
| Western hemlock | 29 lb/cu ft | 540 lbf | Non-durable | No characteristic odor | Indoor infrared and traditional cabins |
| Sitka spruce | 27 lb/cu ft | 510 lbf | Slightly resistant to non-resistant | No characteristic odor | Classic Scandinavian interiors |
| Quaking aspen (untreated) | 26 lb/cu ft | 350 lbf | Non-durable | No characteristic odor | Interior paneling and benches, often thermo treated |
Only the two cedars are rated durable against decay, which is why they dominate outdoor builds. Hemlock, spruce and aspen are fine indoors.
Red cedar vs white cedar sauna
Both cedars come from the same Ontario factory in the Dundalk LeisureCraft range. LeisureCraft’s Canadian Timber Collection page says Eastern white cedar is sourced from Ontario mills and “shares the same natural resistance to moisture and decay” as Western red cedar, which it describes as “richer, more aromatic, and with slightly higher natural oil content.” Both lines use identical construction and hardware, so the choice is mostly color, scent and budget.
Every Canadian Timber sauna we list is Eastern white cedar with tight knots. That includes the Dundalk CT Granby 3 Person Outdoor Sauna CTC66W, whose listing gives 1.5 in. (35 mm) wall and roof boards, the Dundalk CT Georgian 6 Person Outdoor Sauna CTC88, also 1.5 in. solid cedar, the Dundalk CT Harmony 4 Person Barrel Sauna and the Dundalk CT Luna 4 Person Cube Sauna, which uses solid cedar for the floor joists, floor and walls with white cedar bevel siding. We do not currently list LeisureCraft’s Western red cedar Dundalk Collection; call us for a quote.
Clear vs knotty cedar
Grade describes how many knots a board has. Clear boards are knot free or nearly so. Knotty boards, like the tight knot white cedar in the Canadian Timber line, have small, sound knots that give a rustic cabin look. Grade is mainly an appearance choice; species decides decay resistance.
Cedar vs hemlock sauna
Hemlock is a little denser and harder than either cedar, has no characteristic odor and a straight, even look, but The Wood Database rates it non-durable for decay. That makes it a strong indoor wood and a poor choice for exposed outdoor walls. Most of our indoor infrared cabins are hemlock, such as the Viti 2-Person Hemlock Infrared Sauna ($1,999.99 at the time of writing).
If you want cedar scent in an infrared cabin, the Low EMF Two Person Far Infrared Red Cedar Indoor Sauna lists red cedar as its main material and notes that the wood has a natural fragrance and color variation. Comparing heat types? Read infrared vs traditional sauna first.
Is spruce good for a sauna?
Yes, indoors. Osmo, a German wood products maker, calls spruce “the classic for Scandinavian sauna construction.” Low decay resistance keeps it indoors. One example we list is the Carbonized Spruce Traditional Sauna with a 4.5 kW metal stove, whose listing names carbonized spruce as the board material.
Thermo aspen sauna wood and other thermally modified woods
Thermal modification heats wood to make it more stable. Lunawood’s guide says its ThermoWood is “exceptionally dimensionally stable,” resists moisture and dirt, and has “exceptionally low thermal conductivity,” which it links to “pleasantly cool surfaces.” Osmo describes aspen as light colored and practically knot free, a good fit for benches and walls. Dundalk’s indoor CT Element line uses a different thermally modified wood: the CT Element Nook Sauna is built from Thermo Grandis, which the listing says is treated in Ontario for stability and moisture resistance.
Bench wood, smell and allergies
Benches take direct skin contact, so softness and no resin matter most there. Our Luna and Georgian listings use the same white cedar for benches as for walls.
Cedar’s aroma is a big part of its appeal, but it is not for everyone. The Wood Database notes that Western red cedar contains plicatic acid and causes allergic reactions, particularly occupational asthma, more often and more severely than many other commercial woods. That mostly concerns wood dust, but if cedar bothers you, hemlock, spruce or aspen are lower odor choices. Sauna heat is not right for everyone either; check with your doctor before starting if you are pregnant or have a heart, blood pressure or other medical condition.
Finishing: leave the inside bare
Sauna interiors are normally left unfinished. Finnleo’s maintenance page says “Do not paint, varnish, or stain the interior surfaces of your sauna” because “the wood needs to breathe,” and that artificial finishes make the wood hotter and can release fumes. Finnleo allows a sealant on door handles and floor boards and suggests optional paraffin oil on benches. Treat outdoor exteriors per your assembly manual. For routine care, see our guide on how to clean a sauna.
Indoor vs outdoor: a quick decision guide
- Outdoor barrel or cabin: cedar. Eastern white cedar for a lighter, knotty look; Western red cedar for deeper color and stronger scent.
- Indoor infrared cabin: hemlock for neutral scent, red cedar if you love the aroma.
- Indoor traditional room: spruce, hemlock or a thermally modified wood like Thermo Grandis or thermo aspen.
To see the full cedar range, browse our Dundalk LeisureCraft page or read our Dundalk Georgian Cabin Sauna review. Orders of $999 or more ship free by freight. Questions about a specific wood or listing? Call 866-777-2590, Mon-Fri 9AM-6PM PST. Our return and refund policy is posted online.
Frequently asked questions
What is the best wood for a sauna?
For outdoor saunas, cedar, because it is the only common sauna wood rated durable against decay. For indoor saunas, hemlock, spruce, aspen and thermally modified woods all work well, and hemlock suits people who prefer little or no scent.
Red cedar vs white cedar sauna: which lasts longer?
LeisureCraft says both share the same natural resistance to moisture and decay, with Western red cedar having slightly higher oil content.
Is hemlock good for an outdoor sauna?
Hemlock is rated non-durable for decay, so it is best kept indoors. Most hemlock saunas we sell are indoor infrared cabins.
Should I seal the inside of my sauna?
No. Leave interior walls and ceiling bare so the wood can absorb and release moisture. Paraffin oil on benches is optional, and your manual comes first.
