Best Wood Species for Sauna Construction: A Builder's Guide

Choosing the right wood is arguably the single most important decision in sauna construction. The lumber you select determines how your sauna looks, how it feels under bare skin, how it ages over decades, and — critically — how it performs under extreme heat and humidity cycles.

Western Red Cedar — The Gold Standard

Western Red Cedar remains the most popular choice among premium sauna builders in North America, and for good reason. It is naturally resistant to moisture, decay, and insect damage thanks to its high concentration of thujaplicins — natural preservatives embedded in the heartwood. Cedar also has a remarkably low thermal conductivity, which means it stays comfortable to touch even at 190 °F.

The aromatic oils produce a subtle, pleasant scent that many sauna enthusiasts consider essential to the experience. Over time, cedar develops a beautiful silver-grey patina if left untreated, or it can be maintained with a light sanding every few years to preserve its original warm reddish tone.

Alder — The Scandinavian Favorite

Alder has been the go-to sauna wood in Finland and Scandinavia for centuries. It is a hardwood with a fine, even grain and a light honey color that darkens elegantly with heat exposure. Alder's key advantage is its minimal resin content — it will never bleed sap onto your skin, even after years of high-temperature sessions.

Alder also has excellent dimensional stability, meaning it resists warping and cracking through repeated heating and cooling cycles. For clients who want an authentic Nordic aesthetic, alder is our top recommendation.

Hemlock — Clean and Budget-Friendly

Western Hemlock offers a clean, virtually odorless sauna experience at a lower price point than cedar. Its pale, uniform appearance creates a minimalist look that pairs well with contemporary interior design. Hemlock is softer than alder, so it requires careful bench construction to avoid denting, but its low density makes it comfortable underfoot and pleasant to sit on.

Thermowood — Engineered for Performance

Thermally modified timber — commonly called Thermowood — is standard lumber that has been heated to 400 °F+ in a controlled kiln process. This permanently alters the wood's cell structure, reducing its moisture absorption by up to 80% and dramatically increasing its resistance to rot and fungal growth.

Thermowood is the best choice for outdoor saunas or installations in humid climates where long-term durability is the top priority. The modification process gives the wood a rich, dark brown color and a caramelized aroma that many clients find appealing.

Our Recommendation

At RP Restoration, we typically recommend Western Red Cedar for indoor residential saunas and Thermowood for outdoor builds. However, every project is unique — factors like local climate, desired aesthetic, budget, and whether the sauna will be used daily or weekly all influence the optimal choice. During our free consultation, we bring physical samples so you can feel the difference yourself.