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What’s the best wood for a sauna?

Print-style illustration of a carpenter's workbench with stacked cedar boards, a mallet, a hand plane, wood shavings and a coil of cable, a half-paneled sauna wall behind.AI-generated illustration
Short answer · best wood for a sauna

On the numbers, western red cedar leads: in US Forest Service data it’s the lightest, conducts the least heat, shrinks least and resists decay. Aspen, spruce and basswood are close on heat and cost less, with little aroma, but shrink more and don’t resist rot. Thermally modified wood conducts even less heat and holds less moisture.

Checked Sep 23, 2026 · how we check

Sauna woods compared

SpeciesSpecific gravityHeat conduction (W/m·K, 12% moisture)Volume shrinkageDecay resistance
Western redcedar0.330.106.8%Resistant
Quaking aspen0.400.1211.5%Slight or none
Engelmann spruce0.370.1111%Slight or none
Western hemlock0.480.1412.4%Slight or none
Eastern hemlock0.420.129.7%Slight or none
Basswood0.380.1115.8%Slight or none

Source: USDA Forest Products Laboratory, Wood Handbook (2021), chapter 4 (conductivity can vary up to 20%) and chapter 14 (decay classes). Checked Sep 23, 2026.

From US Forest Service data

Is cedar or aspen better for a sauna?

By US Forest Service data, western red cedar is the lightest (specific gravity 0.33), conducts the least heat (0.10 W/m·K), shrinks least (6.8%) and resists decay; aspen is denser (0.40), conducts a bit more (0.12) and shrinks more (11.5%), but has no strong aroma, which some people prefer. Thermally modified wood changes the picture: see below.

Why does thermal conductivity matter on a sauna bench?

Lower-conductivity wood feels cooler to skin at the same air temperature, which is why cedar, aspen and basswood are common for benches.

What is thermo-aspen or thermally modified wood?

Wood heated to about 190–210 °C to change its structure (Thermory, source). Lunawood reports its thermally modified pine and spruce at 0.09 W/m·K vs 0.12 untreated, tested by VTT, with 6–7% equilibrium moisture (source). Thermory says its thermo-aspen doesn’t secrete resin. We found no lab conductivity figure for thermo-aspen itself.

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