Western red cedar, hemlock, and aspen are the best wood types for a DIY sauna because they're low in resin, stay cooler against bare skin, and don't release harmful compounds when heated. Cedar works best for walls and ceilings, while aspen or hemlock are the smarter picks for benches and backrests.
If you're building your own sauna, the wood you choose matters more than most guides let on. It's not just about looks or cost. The wood directly affects how hot the bench gets, how long it lasts, whether it splinters, and—most importantly—whether you're breathing in anything you shouldn't when the temperature hits 180°F.
Here's what the research and experienced builders actually use, and why.
The Short List: Three Woods That Work
For a DIY sauna, you want wood that is low-resin, low-density, and doesn't release volatile organic compounds (VOCs) when heated. Softwoods with tight grain patterns are the standard. Hardwoods tend to conduct too much heat and can feel uncomfortably hot on bare skin.
1. Cedar (Western Red Cedar)
This is the gold standard for a reason. Western red cedar has a natural resistance to moisture, decay, and insects. It doesn't warp easily under high heat and humidity. The wood contains natural oils called thujaplicins that inhibit fungal growth, which is why it lasts for decades in a sauna environment.
From a health perspective, cedar is one of the safest options. It releases minimal VOCs when heated, and the scent—while strong—is not irritating for most people. Some men find the aroma calming, which aligns with research on how certain wood compounds can lower cortisol levels during heat exposure (though the effect is mild and individual).
What to look for: Kiln-dried, clear-grade western red cedar. Avoid "cedar" that is actually juniper or aromatic cedar, which can have stronger oils that may irritate sensitive skin or lungs.
2. Hemlock
Hemlock is a close second. It's a softwood with a straight, even grain that resists splintering. It has very low resin content, meaning it won't ooze sticky sap when the sauna heats up. It also has a neutral odor, which some people prefer over cedar's strong scent.
Hemlock is less expensive than cedar and holds up well in high-moisture environments. It does not contain the same natural fungicides as cedar, so it may require more careful maintenance (proper ventilation and drying between sessions). But for a DIY project on a budget, it's a reliable choice.
What to look for: Kiln-dried hemlock, free of knots and cracks. Avoid "hem-fir" blends, which can include fir species that are higher in resin.
3. Aspen
Aspen is a hardwood, but it's a lightweight one. It has a very tight, closed grain that resists absorbing moisture and odors. That means your sauna won't start smelling like last week's sweat session. Aspen also stays relatively cool to the touch, even at high temperatures, because it doesn't conduct heat as efficiently as denser hardwoods.
The trade-off? Aspen is softer than cedar or hemlock, so it can dent or scratch more easily. It also lacks natural decay resistance, so it needs to be kept dry. But for bench surfaces where you sit, aspen is excellent because it rarely splinters and feels smooth.
What to look for: Kiln-dried aspen, clear grade. Avoid "quaking aspen" that has visible bark inclusions or rot.
Woods to Avoid
Not all wood is safe for sauna use. Here are the ones that should stay out of your build.
Pine and Spruce
These are cheap and common, but they are high in resin. When heated, the resin can seep out of the wood, creating sticky, flammable deposits on the surface. More importantly, pine and spruce release terpenes and other VOCs when heated, which can irritate the respiratory system. Some men report headaches or throat irritation after sitting in a pine-lined sauna. Not worth it.
Pressure-Treated Lumber
Never use pressure-treated wood indoors, especially in a sauna. The chemicals used to treat it include copper, chromium, and arsenic compounds. When heated, these can off-gas into the air you breathe. There is no safe level of exposure in an enclosed, high-temperature space.
Oak, Maple, or Other Dense Hardwoods
These woods are beautiful, but they conduct heat too well. A bench made of oak will feel noticeably hotter than cedar or aspen, and it can cause burns on bare skin. They also expand and contract more with temperature changes, leading to cracks and warping over time.
Redwood
Redwood is sometimes used in saunas, and it is naturally rot-resistant. But it is softer and more porous than cedar, and it can release a reddish pigment when wet that stains skin and towels. It's not dangerous, but it's messy and less durable than cedar for the same price.
What About the Walls vs. the Benches?
You can mix wood types. In fact, many DIY builders do.
- Walls and ceiling: Cedar is the standard. It handles moisture well, looks good, and the scent is pleasant. Hemlock is a solid alternative if you want a neutral smell.
- Benches and backrests: Aspen or hemlock. These are the surfaces you touch. They stay cooler, resist splintering, and don't absorb odors the way cedar can. If you use cedar for benches, expect it to darken and absorb sweat over time.
- Floor: Cedar or hemlock, but expect it to wear faster. Many builders use tile or concrete for the floor and save wood for the benches and walls.
A Practical Note on Sourcing
Not all lumber is created equal. For a sauna, you want kiln-dried wood. Kiln drying removes moisture and kills any insects or fungi that might be living in the wood. It also reduces the risk of warping when the wood is repeatedly heated and cooled.
Grade matters. Look for "clear" or "select" grade, which means fewer knots and defects. Knots can contain resin pockets that weep when heated. They also create weak points that can crack over time.
Where to buy: Local lumber yards often stock cedar and hemlock. Big-box home improvement stores may carry cedar decking, but that is often treated with water repellents or stains that are not safe for sauna use. Ask specifically for untreated, kiln-dried wood suitable for interior use.
The Bottom Line for Your Build
If I were building a DIY sauna today, I would use western red cedar for the walls and ceiling, and aspen for the benches and backrests. That combination gives you durability, safety, comfort, and a pleasant experience without breaking the bank.
If budget is tight, hemlock for everything is a perfectly fine choice. Just avoid pine, spruce, pressure-treated wood, and dense hardwoods.
And before you start cutting, remember: the wood you choose is the surface you'll be sitting on for years. It's worth getting it right the first time.
If you have specific health concerns—particularly respiratory issues or skin sensitivities—check with your doctor before building. Some people are sensitive to cedar oils, and hemlock or aspen may be a better choice for your body.
Frequently asked questions
Why shouldn't you use pine or spruce in a sauna?
Pine and spruce are high in resin, which seeps out when heated and creates sticky deposits on surfaces. They also release terpenes and other volatile organic compounds that can irritate the respiratory system, and some people report headaches or throat irritation after sitting in a pine-lined sauna.
Is cedar or aspen better for sauna benches?
Aspen is generally the better choice for bench surfaces because it stays relatively cool to the touch, rarely splinters, and doesn't absorb odors the way cedar can. Cedar will darken and absorb sweat over time when used for benches, though it remains the standard for walls and ceilings.
Can you mix different wood types in a DIY sauna build?
Yes, many DIY builders mix wood types and it's often the practical approach. A common combination is western red cedar for the walls and ceiling and aspen or hemlock for the benches and backrests. If budget is the priority, kiln-dried hemlock throughout is a reliable option.
What should you look for when buying wood for a sauna?
You want kiln-dried, clear or select grade lumber, which means fewer knots and defects. Knots can hold resin pockets that weep when heated and create weak points that may crack over time. Avoid cedar decking from big-box stores, as it's often treated with water repellents or stains that aren't safe for sauna use.