- Western Red Cedar: Premium choice — aromatic, naturally rot-resistant, beautiful. Most expensive.
- Hemlock: Excellent all-round performer — no aroma, good heat properties, mid-range price. Popular for allergy sufferers.
- Aspen: Lightest colour, very low resin, hypoallergenic. Good budget-to-quality option.
- Thermowood: Heat-treated pine — dark colour, improved stability, good outdoor option at mid price.
- Avoid: Untreated pine (resin drips), MDF, plywood, chipboard — all unsafe in sauna environments.
Why Timber Choice Matters
The timber in a sauna performs under demanding conditions: sustained high temperatures (70–100°C for traditional, 45–65°C for infrared), repeated thermal cycling, and — in the case of steam saunas — significant humidity. Not all timbers handle these conditions equally. The wrong choice results in resin drips, excessive heat absorption causing surface burns, rapid deterioration, or off-gassing of unpleasant chemicals.
Interior sauna timber must be low-resin, dimensionally stable under heat, comfortable to sit on (not burning hot), and free from treatments or finishes that release chemicals when heated. Exterior timber (for outdoor saunas) has different requirements: weather resistance, UV stability, and moisture durability.
Western Red Cedar (Thuja plicata)
The most widely used premium sauna timber in Australia and globally. Western Red Cedar has a naturally occurring oil (thujaplicin) that makes it inherently resistant to moisture, rot, and insects without chemical treatment. It is aromatic — the distinctive cedar smell is pleasant to most people and part of the authentic sauna experience. The deep reddish-brown colour ages beautifully.
✓ Why cedar is the gold standard
- Natural rot and moisture resistance
- Distinctive aromatic scent
- Low density — slow to absorb and radiate heat (comfortable)
- Stable under repeated heat/cool cycles
- Beautiful colour that ages gracefully
- Extremely long lifespan in sauna environment
✗ Considerations
- Most expensive sauna timber — 30–60% premium over hemlock
- Aroma not universally liked (some find it overpowering)
- Can cause reactions in those with cedar sensitivity/allergy
- Canadian supply — price affected by exchange rates
Best for: Premium installations, those who want the authentic cedar aroma, outdoor cabin exteriors, buyers focused on the best long-term outcome.
Typical premium over hemlock: $1,500–$4,000 on a complete interior for a 3–4 person sauna.
Hemlock (Tsuga canadensis)
The most popular choice for mid-range to high-quality kit saunas globally. Hemlock is a fine-grained, pale-coloured timber with very low natural resin content. It has no distinctive aroma — important for users who are scent-sensitive or who find cedar overpowering. Performance in the sauna environment is excellent. Most quality Finnish and North American sauna brands use hemlock as their standard interior timber.
✓ Why hemlock is the smart default
- Excellent thermal performance (low heat absorption)
- No aroma — neutral and accessible
- Stable, dimensionally consistent under heat
- Fine, consistent grain — smooth surface
- Good availability and competitive pricing
- Very long lifespan in sauna environment
✗ Considerations
- Less visually distinctive than cedar
- No natural insect or rot resistance (not needed in dry indoor environment)
- Pale colour shows dirt and dark marks more than cedar
Best for: Most homeowners who want quality without the cedar premium, allergy or scent-sensitive users, those who prefer a clean neutral aesthetic.
Aspen (Populus tremula)
A very light, almost white timber with virtually no resin and no detectable aroma. Aspen is considered the most hypoallergenic sauna timber available — it produces no tannins or aromatic compounds that can cause reactions. It heats up quickly and is comfortable to sit on at high temperatures. Popular in Scandinavian saunas and increasingly available in Australian kit saunas.
✓ Why aspen suits some buyers
- Most hypoallergenic option — no resins, no aroma
- Lightest colour — bright, clean aesthetic
- Very low thermal conductivity — comfortable at high temps
- Competitive pricing in markets where it's available
✗ Considerations
- Less availability in Australian market
- Can show tannin staining over time
- Less visually rich than cedar or darker timbers
- Not as moisture-resistant as cedar (fine for indoor use)
Best for: Allergy or sensitivity sufferers, those wanting maximum neutrality in the sauna environment, buyers who prefer a light Scandinavian aesthetic.
Thermowood (Heat-Treated Pine)
Thermowood is pine or other timber that has been heat-treated at high temperature in the absence of oxygen — a process that breaks down the resin, dramatically reduces moisture absorption, and darkens the timber to a rich brown colour. The result is a stable, resin-free timber well-suited to sauna environments, available at a lower price point than cedar while outperforming untreated pine significantly.
✓ Why thermowood works
- Resin removed by the heat treatment process
- Distinctive dark colour — premium aesthetic
- Improved dimensional stability vs standard timber
- Better moisture resistance than untreated pine
- Good value — mid-range price point
✗ Considerations
- Slightly more brittle than untreated timber
- Can be harder to source in Australia
- Dark colour is distinctive — not to everyone's taste
Best for: Outdoor sauna exteriors where weather resistance matters, homeowners who like the darker Scandinavian aesthetic, mid-range budget with performance focus.
Timbers to Avoid
Untreated pine: Resin softens and drips at sauna temperatures — sticky, unpleasant, and potentially dangerous near a heater. MDF and chipboard: Release formaldehyde and other chemicals when heated. Completely unsuitable. Plywood: Adhesives break down under heat, releasing chemicals. Any sealed or painted timber: Sealants and paints release fumes when heated. Interior sauna timber must always be left untreated and natural.
Timber Maintenance
Interior sauna timber requires very little maintenance. The key rules:
- No sealants, varnishes, or paint on interior surfaces — ever. These release chemicals when heated.
- Wipe down bench surfaces with a dry or lightly damp cloth after each session
- For cedar and hemlock, occasional light sanding (120–180 grit) of bench surfaces when they become rough — typically once or twice a year with regular use
- Allow the sauna to ventilate and dry after each session — leave the door ajar for 30–60 minutes
- Exterior timber on outdoor saunas should be treated with a suitable UV-resistant outdoor timber oil or sealant on a schedule recommended by the manufacturer (typically every 1–2 years)
Some Australian hardwoods can work, but most are less suitable than the traditional sauna timbers. Eucalyptus species are naturally durable but tend to be dense (slow to heat, hot to sit on), heavy, and have higher resin content than softwoods. Spotted gum and blackbutt can work for exterior cladding on outdoor saunas. For interior use, hemlock, cedar, or aspen remain the recommended choices even in Australia — they're available from specialist suppliers and perform reliably.
Timber density and thermal conductivity affect how quickly interior surfaces heat up and how hot they feel to touch and sit on. Dense hardwoods absorb and radiate more heat — surfaces become uncomfortably hot. Low-density softwoods like cedar, hemlock, and aspen absorb heat slowly and remain comfortable even at 90°C+ air temperatures. This is why softwoods are the universal choice for sauna interior lining and bench surfaces.