Knot-free Western red cedar is the best all-round choice for building a sauna, offering natural rot resistance, low heat conductivity, and a mild aroma. Eastern white cedar and heat-treated Nordic pine are strong alternatives depending on where you live and the sauna style you want.
If you're building a sauna, you're already thinking about heat, moisture, and longevity. But the wood you choose isn't just about aesthetics—it affects how the sauna performs, how it smells, and how it feels on your skin. Cedar is the gold standard for a reason. But not all cedar is the same.
Let's break down the types that actually work, why they work, and what to look for at the lumber yard or when ordering online.
Why Cedar? It's Not Just Tradition
Cedar has been the go-to wood for saunas for centuries, especially in Nordic and Baltic cultures. The reasons are practical, not sentimental.
First, cedar is naturally rot-resistant. Saunas are wet environments. Even with good ventilation, moisture cycles through the wood daily. Cedar contains natural oils—thujaplicins and phenols—that resist fungal growth and decay. That means your sauna walls won't warp, crack, or develop mold as fast as softer woods like pine or spruce.
Second, cedar is a poor conductor of heat. When you lean against a cedar bench at 180°F, it feels warm but not scorching. That's because cedar's cellular structure traps air, slowing heat transfer. Compare that to oak or maple, which can burn your skin at the same temperature.
Third, cedar smells good. That's not just a luxury. The aromatic compounds in cedar have been shown in some studies to have mild antimicrobial properties (Cheng et al., Bioresource Technology, 2005). The scent itself is calming—part of the reason sauna sessions feel restorative. You're not just sweating; you're breathing in compounds that have been used in traditional medicine for respiratory support.
The Three Cedars That Work for Saunas
Not every tree called "cedar" is actually a true cedar. The lumber industry uses the name loosely. For sauna building, stick with these three.
1. Western Red Cedar (Thuja plicata)
This is the most common sauna wood in North America. It's light, easy to work with, and naturally resistant to moisture and insects. Western red cedar has a straight grain and a warm reddish-brown color that ages to a silvery gray if left unfinished.
Why it works: Low density means it doesn't hold heat. It expands and contracts less than many hardwoods, which matters when you're cycling between dry heat and steam. It also has a mild, pleasant aroma that isn't overpowering.
What to watch for: Knots. Some grades of Western red cedar have knots that can ooze resin when heated. Resin is sticky, can stain skin, and can create hot spots. Look for "clear" or "knot-free" grades for benches and interior walls. For framing or exterior siding, knots are less of an issue.
2. Eastern White Cedar (Thuja occidentalis)
Less common but equally effective. Eastern white cedar is lighter in color—pale yellow to almost white—and has a finer, more uniform grain than Western red cedar. It's also slightly softer, which makes it easier to sand and shape.
Why it works: It has a higher natural oil content relative to its density, which gives it excellent moisture resistance. Some sauna builders prefer it for benches because it stays cooler to the touch than denser woods.
What to watch for: Availability. Eastern white cedar is more common in the northeastern U.S. and Canada. If you're in the Midwest or West, you might pay a premium for shipping. It's also softer, so it can dent more easily than Western red cedar if you drop tools or heavy buckets.
3. Finnish Cedar (Pinus sylvestris - often called "Nordic Spruce" or "Scots Pine" in the trade)
Strictly speaking, this isn't a true cedar. But in the sauna world, "Finnish cedar" usually refers to heat-treated or naturally resinous Scots pine grown in northern Finland. The cold climate slows growth, producing tight grain rings and high resin content.
Why it works: Traditional Finnish saunas use this wood. It's dense, durable, and develops a rich, warm patina over time. The resin, when heated, releases a distinct pine scent that many sauna enthusiasts prefer over cedar's sweeter aroma.
What to watch for: Resin bleed. This wood can weep sap when it gets hot. That's normal, but it can be annoying if you're sitting on a bench that's sticky. Some builders pre-bake the wood in a kiln to stabilize the resin. If you're buying Finnish cedar, ask if it's been heat-treated.
What to Avoid
Not every wood belongs in a sauna. Avoid:
- Pressure-treated lumber. It contains chemicals like copper, chromium, and arsenic that can off-gas when heated. You don't want to breathe that in while you're sweating.
- Plywood or MDF. These are made with glues and resins that release formaldehyde at high temperatures. Not safe.
- Hardwoods like oak, maple, or hickory. They conduct heat too well. You'll burn your skin on the benches. They also expand and contract more dramatically with moisture changes, leading to warping.
- Redwood. It's rot-resistant but soft and can splinter easily. It's also less aromatic than cedar and can darken unevenly with heat.
A Note on Grain Orientation and Bench Comfort
When you're building benches, pay attention to how the wood is cut. Quarter-sawn cedar—where the grain runs vertically—is more stable and less likely to cup or twist over time. It also feels smoother to the touch.
Flat-sawn cedar is cheaper and more common, but it's more prone to warping. If you're on a budget, flat-sawn is fine for walls or ceilings. Just use quarter-sawn for anything you'll sit or lie on.
Practical Takeaway
If you want the best balance of performance, cost, and availability, go with knot-free Western red cedar for the interior. It's the standard for a reason.
If you're in the Northeast and can source it, Eastern white cedar is a strong alternative that's slightly more affordable.
If you want to replicate a traditional Finnish sauna, look for heat-treated Nordic pine—but be prepared for resin management.
One last thing: whatever wood you choose, don't seal it. Sauna wood needs to breathe. Varnishes, polyurethanes, or paints trap moisture and create a breeding ground for mold. The wood will darken naturally over time. That's not a defect. That's a sauna that's been used.
Disclaimer: This information is for educational purposes. Building a sauna involves structural, electrical, and safety considerations. Consult a licensed contractor or architect for your specific project.
Frequently asked questions
Why is cedar good for saunas?
Cedar contains natural oils that resist fungal growth and decay, making it well suited to the wet, high-heat environment of a sauna. Its cellular structure also traps air, which slows heat transfer so the wood feels warm rather than scorching against skin. The aromatic compounds in cedar have shown mild antimicrobial properties in some studies.
What grade of cedar should I use for sauna benches?
Use clear or knot-free grades for benches and interior walls. Knots in lower grades can ooze resin when heated, which is sticky, can stain skin, and can create hot spots. For framing or exterior work, knots are less of a concern.
Should I seal or varnish sauna wood?
No. Sauna wood needs to breathe, and varnishes, polyurethanes, or paints trap moisture and create conditions for mold. The wood will darken naturally over time with use, which is normal and expected.
What wood should I avoid in a sauna?
Avoid pressure-treated lumber, which can off-gas chemicals like copper, chromium, and arsenic when heated. Plywood and MDF contain glues that release formaldehyde at high temperatures. Hardwoods like oak, maple, and hickory conduct too much heat and can burn skin on contact with benches.