If you've looked into buying or building a sauna, you've noticed cedar is the default recommendation. There's a reason for that, and it's not just tradition or marketing.
Cedar works better for saunas than almost any other wood. The reasons range from practical physics to chemistry that affects what you're actually breathing in while you sit in 180-degree heat. Here's what the research and experience show.
Cedar handles heat and moisture differently than other woods
Saunas cycle between extreme heat and high humidity, then dry out completely. Most woods can't handle that without warping, cracking, or rotting.
Cedar has a cellular structure that resists moisture absorption. The wood contains natural oils that make it less porous than pine, spruce, or fir. When you pour water on hot sauna stones, that steam hits the walls. Cedar absorbs less of that moisture, which means it dries faster and doesn't swell or shrink as dramatically as other woods.
A 2021 study on wood performance in high-humidity environments found that Western Red Cedar showed 40% less dimensional change than Douglas fir under the same conditions (Forest Products Journal, 2021). That matters when you're building a structure that needs to hold together through thousands of heating and cooling cycles.
Pine, by contrast, can warp within months in a sauna. It also bleeds resin when heated, which creates sticky spots on the walls and benches that are unpleasant to sit on.
The smell is not just pleasant-it has a function
That cedar smell people associate with saunas comes from natural compounds called phthalides and thujaplicins. These are volatile organic compounds (VOCs) that release when the wood is heated.
Here's where it gets interesting from a health perspective. Thujaplicins have demonstrated antimicrobial properties in laboratory studies. A 2018 review in the Journal of Wood Science found that cedar extracts showed measurable antibacterial activity against several common bacterial strains, including Staphylococcus aureus. The heat of a sauna accelerates the release of these compounds.
Does that mean cedar saunas are sterile environments? No. But the combination of high heat and natural antimicrobial compounds creates an environment where mold and bacteria have a harder time establishing themselves compared to other wood surfaces.
The scent itself also affects the experience. The aroma of cedar has been associated with reduced sympathetic nervous system activity in small studies. One 2015 study measured heart rate and cortisol levels in participants exposed to cedarwood essential oil and found both decreased compared to controls. The effect was modest but measurable.
Cedar is naturally resistant to decay without chemical treatment
This is the big one. Cedar contains natural preservatives called tropolones, specifically beta-thujaplicin. These compounds are fungicidal and insecticidal. That means cedar resists rot and insect damage without needing chemical pressure treatment.
This matters for your health. Treated lumber used in outdoor construction often contains copper-based preservatives or, in older wood, chromated copper arsenate. When you heat treated wood, those chemicals can volatilize into the air you're breathing.
A 2019 study from the National Institute for Occupational Safety and Health found that burning or heating pressure-treated wood released arsenic and chromium compounds. The concentrations decreased with distance from the source, but in an enclosed sauna, you're in close proximity to the wood surface.
Cedar eliminates that concern entirely. It protects itself biologically, not chemically.
Cedar stays cooler to the touch
This is a practical safety consideration. Cedar has lower thermal conductivity than hardwoods like oak or maple. When the sauna is at 190 degrees, the cedar bench you're sitting on will be hot, but not as hot as a hardwood bench would be at the same air temperature.
Thermal conductivity of Western Red Cedar is approximately 0.11 W/mK. Oak is about 0.17 W/mK. That difference means cedar transfers heat to your skin more slowly. It's the difference between sitting on a surface that feels warm versus one that feels like it's burning.
For sauna builders, this also means cedar doesn't transfer heat to the structure of the building as efficiently, which improves insulation performance.
Not all cedar is the same
When people recommend cedar for saunas, they're usually talking about Western Red Cedar (Thuja plicata) or, less commonly, Eastern White Cedar (Thuja occidentalis). These are the species that have been used in Finnish and Scandinavian sauna traditions for generations.
Spanish cedar, aromatic cedar, and other species sold as "cedar" are different genera entirely. Spanish cedar is actually a type of mahogany. It smells pleasant but doesn't have the same moisture resistance or antimicrobial properties. Red cedar used for closet linings is a different species (Eastern Red Cedar, Juniperus virginiana) and can be too resinous for sauna use.
If you're building or buying a sauna, look for Western Red Cedar specifically. It's the species with the longest track record and the most research behind it.
What about other woods?
Cedar is not the only option. Finnish saunas traditionally used spruce, pine, or alder. These woods work, but they require more maintenance and don't last as long.
Hemlock and aspen are alternatives that some modern sauna builders use. They're less aromatic than cedar, which some people prefer, but they don't have the same natural decay resistance.
Thermally modified woods-woods heated to high temperatures in a low-oxygen environment to change their cellular structure-are another option. The thermal modification process makes wood more moisture-resistant and stable, but it also makes it more brittle and can reduce its lifespan compared to naturally durable species like cedar.
The practical takeaway
Cedar is recommended for sauna construction because it solves three problems simultaneously: moisture resistance, decay resistance without chemicals, and thermal comfort. The antimicrobial and aromatic properties are bonuses.
If you're building a sauna, cedar costs more upfront than pine or spruce. But it will last longer, require less maintenance, and you won't be breathing fumes from chemical treatments or resin bleed. For most people, the trade-off is worth it.
If you already have a sauna made from a different wood, don't panic. Pine saunas work fine-they just need more ventilation, more frequent cleaning, and you'll want to check for warping or resin buildup periodically. The wood choice matters, but it's one variable among many. Your sauna frequency, session length, and post-sauna recovery habits will have a bigger impact on your health than the species of wood on the walls.
As with any health-related decision, consult a medical professional before starting a sauna routine, especially if you have cardiovascular conditions or are taking medication that affects blood pressure.