Sauna Wood Types Explained: Cedar, Aspen, Hemlock, Spruce and More
You don't need the same wood everywhere in a sauna.
The wood on your walls doesn't have to be the wood on your bench, and an outdoor build has different jobs for wood to do than a dry indoor cabin does. Most sauna shopping guides compare heaters, kW output, and infrared vs. traditional — almost none explain that the wood itself is a real spec, not just a finish. It affects how hot the bench feels against bare skin, what the room smells like, and how well it holds up over years of heat and humidity. Here's how to choose it by application, not by a single "best sauna wood" ranking.
- Benches and backrests: aspen, alder, or abachi — smooth, low-resin, comfortable for direct skin contact.
- Walls and ceilings: cedar, spruce, or hemlock — the aroma and look you want, not a performance requirement.
- Outdoor builds: cedar or thermally modified wood, but only as part of a properly detailed building envelope.
- Cedar's trade-off is its aroma, not a general health risk — the documented respiratory concerns involve occupational sawdust exposure, not finished-sauna use.
- Thermally modified wood ("thermo-aspen," "thermo-spruce") is a heat-treatment process, not a species — it improves moisture resistance and stability at a higher cost.
Sauna wood at a glance
| Wood | Best for | Aroma | Why choose it |
|---|---|---|---|
| Cedar | Walls + exterior | Strong | Durable, distinctive scent |
| Hemlock | Walls + ceilings | Mild | Clean, neutral look and scent |
| Spruce | Walls + ceilings | Light | Traditional Nordic feel |
| Aspen | Benches | Very mild | Smooth, low-resin |
| Alder | Benches | Mild | Warm tone, smooth feel |
| Abachi | Benches | Very mild | Lightweight, low-resin |
What is the best wood for a sauna?
There isn't one best sauna wood for every application. Cedar, spruce, and hemlock are common choices for walls and ceilings, while aspen, alder, and abachi are common choices for benches and backrests. For outdoor saunas, exterior durability and the building envelope matter just as much as the species itself.
Best wood for sauna benches
Aspen, alder, and abachi are common choices for benches, backrests, and headrests. All three are commonly chosen for their smooth feel and relatively low resin content, which is why they're generally preferred for direct skin contact — though comfort also depends on lumber grade, board thickness, and how close the bench sits to the heater, not species alone.
Best wood for sauna walls and ceilings
Cedar, spruce, and hemlock are common wall and ceiling choices. Cedar brings a distinct aroma and natural durability, spruce gives a traditional Nordic look, and hemlock is the pick for buyers who want a cleaner, more neutral-smelling room.
Best wood for an outdoor sauna
Western red cedar and properly specified thermally modified wood are common exterior-cladding choices. But wood species is only part of the story outdoors — a roof with real overhangs, flashing, drainage, a raised base, and ventilation matter just as much. No species choice compensates for a poorly detailed building envelope.
Cedar vs. hemlock: what's the difference?
This is the comparison most buyers are actually trying to make.
Cedar
The classic, recognizable sauna scent, natural durability, and a premium look — but the aroma is polarizing, and it costs more.
Hemlock
Close to aroma-neutral, clean and modern-looking, generally more affordable — a less distinctive, less "traditional-feeling" material, not a lesser one.
Does cedar smell too strong? For some people, yes — that's a real, common reason buyers choose hemlock instead. Separately, Western red cedar wood dust has been linked to asthma and rhinitis in woodworkers with years of occupational sawdust exposure, with plicatic acid implicated in those reactions. That's a very different level of exposure than sitting in a finished cedar sauna, and it isn't a reason to rule cedar out for most people. If you or a regular user has a known sensitivity to cedar or fragrance generally, hemlock is the easy substitute.
Choose hemlock if: you want a neutral-smelling, modern-looking room, or you're managing a scent sensitivity.
Aspen vs. alder vs. abachi for benches
All three are commonly chosen for their smooth feel and relatively low resin content, so the differences come down to look, cost, and sourcing:
- Aspen — pale, very mild scent, the most common default bench wood.
- Alder — slightly warmer tone, mild scent, a popular Scandinavian choice.
- Abachi — lightweight, very mild in aroma, and commonly used for sauna benches and infrared interiors.
There isn't a wrong answer among the three — this is largely a matter of look and sourcing preference once you're past the "avoid cedar-level aroma" decision.
What is thermally modified wood?
"Thermo-aspen" or "thermo-spruce" isn't a different tree — it's wood that's been heat-treated to change how it handles moisture. Thermally modified wood absorbs less moisture and is more dimensionally stable than untreated wood, which is why it holds up better through repeated heat-humidity cycles and can be a strong pick for outdoor cladding. The trade-offs: it costs more, the color darkens, and it's somewhat less structurally strong than the untreated version — good drainage and exterior detailing still matter even with thermo wood.
Can you mix wood species in one sauna?
Yes, and it's the norm rather than the exception. A typical high-quality build pairs cedar, spruce, or hemlock on the walls and ceiling with aspen, alder, or abachi on the benches — each material doing the job it's actually best suited for.
What to check before you buy, regardless of species
- Is the wood properly dried and acclimated before installation?
- Is it low-knot or clear grade, especially anywhere it'll touch skin?
- Is it sanded smooth, with no rough milling on bench surfaces?
- Is it left unfinished (correct for most sauna interiors) rather than painted or chemically treated?
- Is the bench properly spaced and supported for the wood's stability characteristics?
A premium species in a poor grade, or a well-built bench in a badly sourced species, both undercut what you're actually paying for.
How Marterra specs wood
We don't treat wood as a cosmetic upgrade. We look at where the sauna will live, whether you want a neutral or aromatic interior, who'll be using it, and which surfaces will be in direct skin contact — then match construction to that, not just to a price point.
It's also why every sauna we currently carry from SaunaLife and Revive Plunge uses thermally modified wood rather than raw, untreated timber — the stability and moisture-resistance trade-off described above is one we've already made on your behalf.
How our saunas compare
SaunaLife CL3G Cube
Benches: Knot-free Thermo-Aspen
SaunaLife EE6G Ergo Elegance Barrel
Benches: Knot-free Thermo-Aspen
Revive Plunge 2-Person Traditional
Let's talk through your space, not just the spec sheet.
We'll help you compare materials, heater requirements, installation considerations, and the sauna models that make sense for your space.
Book a free 15-minute consultationFAQ
Does sauna wood affect how hot a bench feels?
Yes. Species, moisture content, board thickness, and heater proximity all affect surface temperature. Aspen, alder, and abachi are the standard low-resin, comfortable choices for benches.
Is cedar bad for people with allergies?
Not inherently — the strongest evidence concerns occupational wood-dust exposure, not sauna use. People with a known cedar or fragrance sensitivity often prefer hemlock, aspen, alder, or abachi instead.
Is hemlock a "cheaper" or lesser wood?
No — it's a legitimate choice, not a compromise. It's simply lower in aroma and generally more affordable than cedar, which makes it the better fit for some buyers rather than a lesser one.
What is thermally modified wood?
A heat treatment, not a species — it makes wood more moisture-resistant and dimensionally stable, at a higher cost and with a darker finish.
Can I mix wood species in one sauna?
Yes — it's standard practice to use one species for walls/ceiling and a different one for benches.
Do I need cedar for an outdoor sauna?
Cedar or thermally modified wood are common choices, but roof design, drainage, and ventilation matter as much as species for outdoor durability.
Do knots matter in sauna wood?
Yes — knots run hotter, feel rougher, and can carry more resin. Clear or low-knot stock is the better choice for benches and backrests specifically.
Continue reading
Sources & further reading
- Čermák, P., Rautkari, L., Horáček, P., Saake, B., Rademacher, P., and Sablík, P. "Analysis of Dimensional Stability of Thermally Modified Wood Affected by Re-Wetting Cycles." BioResources 10(2), 2015:3242–3253.
- Mitchell JC, Chan-Yeung M. "Contact allergy from Frullania and respiratory allergy from Thuja." Canadian Medical Association Journal. 1974;110(6):653–654, 657. PMC1947352.
- Occupational wood-dust health effects reference data, CDC/NIOSH. stacks.cdc.gov/view/cdc/179915.
This article is for general informational purposes and reflects publicly available wood-science and occupational health literature current as of publication. It does not replace product-specific guidance from a manufacturer or a qualified professional. Always confirm wood species and construction details for a specific unit with the manufacturer before purchase.