Choosing Sauna Wood: A Practical Guide to Species, Treatment, and Performance

Choosing sauna wood is about more than aesthetics. The right wood affects comfort, durability, and how enjoyable each session is. Because saunas operate under high heat and humidity, wood needs to stay stable, feel good against skin, and be carefully selected to minimize resin.

Whether you’re planning an entirely custom build, or shopping for a pre-built sauna, it’s helpful to have starting knowledge of different wood types and what they can offer. Here are a few tips to keep in mind as you select wood for your dream sauna: 

Step 1: Select the Best Woods for Benches and Seating

Because benches and backrests experience the most heat and skin contact, comfort and heat resistance are the top priorities. Denser species like oak and ash can get uncomfortably hot, so avoiding high-density woods is the best course. Softwoods that remain relatively cool to the touch and are free of knots and resin pockets are the gold standard for seating. Consider Aspen, Alder, or some of the other species described below. 

Step 2: Choose Wood for Walls and Ceilings 

For walls and ceilings, durability and value are top priorities. These surfaces don't require the same "cool touch" properties as benches, allowing for denser or more aromatic woods. High-quality selections ensure the structure remains stable through thousands of heating cycles. Spruce, Canadian Western Red Cedar, and several other species detailed below are great choices. 

Step 3: Consider Aroma and Natural Resistance 

If aroma and built-in protection are priorities, consider Canadian Western Red Cedar. Western Red Cedar resists decay, insects, and moisture indoors and outdoors and releases an earthy, calming scent when heated. Hemlock is also a durable, stable interior choice. While less resistant to decay and moisture than Cedar, it has a neutral scent profile ideal for people with allergies or sensitivities.

Thermally modified woods have the most dimensional stability are also highly decay- and moisture-resistant, making them reliable interior and exterior choices. 

Step 4: Explore Thermal Modification for Longevity 

For enhanced durability and resistance to heat, moisture, diseases, rot, and insects, consider thermally modified woods. Thermal modification heats wood to 160–215°C in a low-oxygen, steamy environment, permanently altering its cellular structure without chemicals. This process improves dimensional stability, provides deep color throughout the wood, and greatly reduces moisture absorption, movement, and warping.

Woods that are thermally modified typically have “Thermo” in the name, such as “Thermo-Aspen” or “Thermo-Alder.” 

Premium Wood Choices for Your Sauna 

Selecting the right combination of materials is critical for balancing durability with a comfortable, rejuvenating sauna experience. Your best choices depend on your preferences and budget. Here are the top species favored for their heat resistance, stability, and aesthetic appeal: 

• Aspen: Known for its light, creamy-white appearance and knot-free texture, Aspen is a staple for sauna benches because it remains cool to the touch even in extreme heat. While it is naturally hypoallergenic and resin-free, its pale color can show stains more easily and require regular maintenance.
• Alder: Offering a warm, reddish tone and a smooth, consistent texture, Alder is a popular choice for interior wall cladding and seating. It provides excellent dimensional stability and resists cracking in humid environments, though it’s slightly denser than Aspen.
• Spruce: A budget-friendly, aromatic option that creates a timeless feel for interior and exterior walls and ceilings. While high-quality Nordic spruce is durable and provides great thermal insulation, it contains small knots that can occasionally release resin during high-heat sessions, particularly in lower-grade material.
• Hemlock: This durable option is prized for its uniform, neutral appearance and for being resin-free and low-odor. It’s a versatile choice for all-around interior use, though it lacks the natural rot resistance of cedar and performs best when the sauna is kept well-ventilated.
• Canadian Western Red Cedar: Renowned for its natural resistance to decay, pests, and moisture, Red Cedar is ideal for sauna exteriors and interior aromatic wall cladding. Its low density helps it feel cooler on the skin, but its high natural oil content can occasionally trigger sensitivities in users with allergies.
• Thermo-Aspen: By undergoing an organic thermal modification process, this wood gains a rich, golden-brown color and enhanced durability. It’s an exceptionally stable choice for benches and interior/exterior cladding, as it resists moisture and warping.
• Thermo-Alder: Boasting a deep, chocolatey hue and superior moisture resistance, Thermo-Alder is a premium choice for seating and interior/exterior wall cladding. It offers an inviting atmosphere with a reduced risk of warping, and while it typically carries a higher price point, its longevity makes it ideal for high-traffic areas.
• Thermo-Spruce: Thermal modification reduces natural resins, increases the R-value and darkens the wood, creating a more stable, insulating and rot-resistant material for indoor/outdoor sauna walls compared to untreated spruce.
• Thermo-Magnolia: Featuring a stunning grain and velvety finish, Thermo-Magnolia offers a unique and luxurious choice for high-end sauna interiors, including walls, ceilings, and benches. Thermal treatment enhances its natural stability and moisture resistance while deepening its color, though its rarity often places it at a higher price point.
• Thermo-Radiata Pine: Highly prized for its bold grain and lack of knots, this wood adds a sophisticated look to interior walls and benches. It’s virtually resin-free and highly durable, but because the thermal process increases its hardness, it typically requires pre-drilling. 

PROSAUNAS offers a wide variety of expertly selected, precision-milled European sauna woods. Their specialists are happy to help with questions about thermal modification, wood selection, or finding the best combination of materials for your sauna.

By choosing the right species, matching materials to their use, and investing in high-quality processing, you can create a sauna that feels comfortable, performs reliably, and stays beautiful for decades to come.