Thermowood vs Cedar Sauna: Which is the Right One for You?

Choosing the right wood for your sauna is an important step in creating a personal sanctuary for relaxation and rejuvenation. Thermowood and cedar are two of the most popular choices, each offering distinct advantages and characteristics. This comprehensive guide explores thermowood vs. cedar saunas.

We’ll explore the pros and cons of each material, including durability, aesthetics, maintenance requirements, and suitability for different climates and sauna types. Whether you’re a seasoned sauna enthusiast or embarking on your first sauna build, this page gives you the knowledge to make an informed decision and choose the ideal wood for your dream sauna experience.

Overview of Thermowood

Thermowood offers superior dimensional stability and lower long-term maintenance; cedar delivers a lower upfront cost and a classic aromatic sauna experience. The right choice depends on your climate, budget, and how often you’ll use the sauna.

Thermowood is lumber kiln-dried at temperatures between 185°C and 215°C in a steam-and-heat process that permanently alters the wood’s cell structure. This process, not a chemical treatment, is what gives thermowood its enhanced stability and rot resistance.

Are Thermowoods Good for Saunas?

Thermowood has become a popular choice for sauna construction, offering a compelling alternative to traditional cedar. Below is a straightforward breakdown of where thermowood excels and where it falls short.

Advantages of Thermowood:

• Durability: Thermowood undergoes a heat treatment process that significantly enhances its dimensional stability and resistance to warping, cracking, and rot. The heat treatment drives out resins and reduces the wood’s equilibrium moisture content (EMC) from roughly 18-20% in untreated wood to 4-6%, which is why thermowood resists swelling and shrinking even under repeated sauna heating cycles. This makes it ideal for withstanding the fluctuating temperatures and humidity levels of a sauna environment.

• Low Maintenance: Because thermowood’s EMC is so low, it doesn’t require the periodic oiling cedar needs to prevent surface checking, a meaningful advantage for commercial operators or anyone who wants a set-and-forget interior. Its reduced moisture content also minimizes the risk of mold growth.

• Improved Aesthetics: Thermowood boasts a beautiful, rich brown color that adds a modern touch to any sauna. This color tends to darken slightly over time, developing a warm, aged patina.

• Comfortable Feel: Thermowood offers a smooth and splinter-resistant surface that feels pleasant on the skin, even at high sauna temperatures.

• Versatility: Thermowood’s stability makes it suitable for various climates, unlike cedar, which can perform less optimally in very humid environments.

• Sauna Type Compatibility: Thermowood suits all sauna types, including dry saunas, steam saunas, and infrared saunas.

Disadvantages of Thermowood:

• Higher Cost: Thermowood typically costs 20-40% more per linear foot than comparable cedar grades, though this gap narrows over a 10-15 year ownership horizon when you factor in maintenance costs.

• Less Traditional Look: While aesthetically pleasing, thermowood’s rich brown color deviates from the classic light wood tones often associated with saunas.

• Limited Availability: Thermowood may not be as readily available as cedar in all regions.

• Scent: Unlike cedar, thermowood has no natural aroma. Some sauna users consider the cedar fragrance an integral part of the experience.

Use Cases:

Thermowood shines in saunas where durability, low maintenance, and a modern aesthetic are priorities. It’s a strong choice for:

• High-use saunas: Gyms, commercial spas, or frequently used home saunas benefit from thermowood’s exceptional resistance to wear and tear.

• Humid Climates: In high-humidity areas, thermowood’s stability makes it a more reliable option than cedar, which can warp in such conditions.

• Modern Sauna Designs: Thermowood’s rich brown color complements modern and contemporary sauna design styles.

How Is Thermowood Made? The Heat Treatment Process Explained

Thermowood is not a species; it’s softwood lumber permanently modified through a three-stage industrial heat treatment process developed in Finland in the 1990s. The VTT Technical Research Centre of Finland pioneered the process, and the Finnish ThermoWood Association holds the ThermoWood® trademark.

The treatment works in three stages. First, the wood is rapidly heated and dried using steam to prevent surface cracking. Second, the temperature is raised to between 185°C and 215°C in a low-oxygen, steam-saturated environment. This is the modification stage where the wood’s cell structure is permanently altered. Third, the wood is slowly cooled and re-moisturized to bring it back to a workable state.

What makes this process significant for sauna builders is what it does to the wood’s chemistry. The high heat breaks down the hemicellulose in the wood’s cell walls, the component most responsible for absorbing and releasing moisture. The result is a dramatic reduction in equilibrium moisture content (EMC), from roughly 18-20% in untreated softwood down to 4-6%. That lower EMC directly reduces the swelling, shrinking, and warping that repeated sauna heating cycles would otherwise cause.

Critically, the entire process is chemical-free. No preservatives, adhesives, or synthetic treatments are introduced at any stage, which is why thermowood carries a Class D durability rating and is considered safe for high-temperature, skin-contact environments like sauna benches and wall cladding. If you’ve seen the term “thermo ayous” in sauna product listings, it refers to African Ayous (Obeche) wood that has undergone the same heat-treatment process; it’s a lighter-colored option gaining traction as a thermowood sauna species.

What Types of Thermowoods are Used for Saunas?

Thermowood can be produced from various softwoods, each offering slightly different characteristics. Here are the most common types used for saunas,

• Thermowood Pine: Thermowood pine is typically the most affordable thermowood option and is well-suited for wall and ceiling cladding. Its treated color ranges from golden-brown to medium brown, and it holds its shape well in the wet-dry cycles of a steam sauna. A popular choice for budget-conscious sauna builders who still want the performance benefits of heat-treated wood.

 

• Thermowood Aspen: Aspen’s naturally low resin content means it stays cool to the touch even at high bench temperatures, a practical advantage for benches and backrests where skin contact is constant. Thermowood Aspen is the closest thermowood equivalent to the feel of traditional Finnish sauna wood, and its light tone creates a bright, airy interior.

• Thermowood Spruce: Spruce has a tighter grain than pine, which gives it a slightly smoother finished surface. It is a common choice for sauna bench slats where a clean, uniform appearance is desired, and its neutral color tone complements a wide range of sauna design styles.

• Thermowood Alder: Alder is gaining popularity as a thermowood sauna species because of its very low density, which means it heats up quickly and stays relatively cool on the surface. It is often used as a premium alternative to aspen for bench construction.

Is Cedar Good for Saunas?

Cedar is a proven sauna wood with a long track record, but not all cedar is the same, and the species you choose matters more than most buyers realize.

Advantages of Cedar:

• Natural Fragrance: Cedar’s aroma comes from thujaplicin, a natural oil that also contributes to its antimicrobial and insect-repellent properties. This oil gradually diminishes with age and heavy use, but for many sauna enthusiasts it remains an integral part of the experience.

• Moisture Resistance: Cedar naturally resists moisture and mildew growth, making it well-suited for sauna environments.

• Insulation: Cedar offers good insulating properties, helping to retain heat within the sauna and supporting energy efficiency.

• Comfortable Feel: Cedar has a smooth texture that feels pleasant on bare skin, even at high sauna temperatures.

• Aesthetics: Cedar’s light wood tone adds a natural, classic look to any sauna design.

• Versatility: Cedar works well in dry, steam, and infrared saunas.

• Affordability: Compared to thermowood, cedar is generally a more affordable upfront option.

Cedar Species Comparison

Not all cedar performs identically in a sauna environment. Here’s how the three most common species compare:

• Western Red Cedar (Thuja plicata): The most common sauna cedar in North America. Lightweight, aromatic, and naturally resistant to decay. Grades range from clear (knot-free, premium) to knotty (more affordable). Typical sauna-grade Western Red Cedar costs $4-$8 per linear foot. Western Red Cedar is widely available across the US and Canada, including from suppliers in Delta, BC, Canada, which is a major production hub for this species.

• Eastern White Cedar (Thuja occidentalis): Denser and slightly less aromatic than Western Red Cedar. More commonly available in the northeastern US and Canada. A solid option where Western Red Cedar is scarce or where a tighter grain is preferred.

• Alaskan Yellow Cedar (Cupressus nootkatensis): The most durable cedar species, with natural oils that rival thermowood’s rot resistance. Significantly more expensive than Western Red Cedar but can last 20-30 years in a well-maintained sauna.

Disadvantages:

• Maintenance: Cedar requires regular cleaning and occasional oiling to maintain its properties and appearance. In a home sauna, plan on oiling every 1-2 years; commercial settings may require more frequent attention.

• Warping: Untreated Western Red Cedar in a high-use sauna typically shows surface checking and graying within 5-8 years without regular oiling and cleaning. Cedar is more susceptible to warping in high-humidity environments than thermowood.

• Durability: Cedar is durable, but it does not match thermowood’s longevity in high-use or high-humidity conditions.

• Limited Availability: Certain cedar grades and species, particularly clear-grade Western Red Cedar, may have limited availability in some regions.

Use Cases:

Cedar remains a strong choice for saunas in many situations, particularly:

• Home Sauna Kits: For personal or family use, cedar offers a well-rounded balance of affordability, aesthetics, and performance.

• Dry Saunas: Cedar’s natural moisture resistance makes it well-suited for dry sauna environments.

• Traditional Style Saunas: Cedar’s classic look and natural thujaplicin aroma contribute to a timeless, authentic sauna experience.

However, cedar might not be the best choice for:

• High-Use Saunas: In gyms or commercial settings with frequent use, thermowood’s superior durability is the more practical option.

• Humid Climates: In areas with very high humidity, cedar’s susceptibility to warping and surface checking is a real concern.

• Those Who Prefer Low Maintenance: If minimal upkeep is a priority, thermowood’s reduced need for oiling is a meaningful advantage.

Thermowood vs Cedar, Side-by-Side Comparison

Choosing between thermowood and cedar comes down to your priorities. Here’s a table summarizing the key differences,

Feature	Thermowood	Cedar
Durability	Excellent	Good
Maintenance	Low	Regular cleaning and occasional oiling
Cost	Higher upfront	More affordable upfront
Aesthetics	Modern, rich brown color	Classic, light wood tone
Feel on Skin	Smooth, splinter-resistant	Smooth, comfortable
Moisture Resistance	Excellent	Good
Warping Resistance	Excellent	More susceptible, especially in high humidity
Sauna Type Compatibility	All types (dry, steam, infrared)	All types (dry, steam, infrared)
Lifespan	25-30+ years with minimal maintenance	15-20 years with regular oiling and cleaning
Scent/Aroma	None	Strong natural cedar aroma (thujaplicin)
Best Use Cases	High-use saunas, humid climates, modern designs	Home saunas, dry saunas, traditional style, budget-conscious

Here’s a quick guideline to help you decide:

• Prioritize durability and low maintenance: Choose thermowood.

• Value affordability and a classic look: Choose cedar.

• Focus on a modern aesthetic and excellent performance in any climate: Thermowood is worth the higher upfront cost.

• Building a home sauna for occasional use: Cedar can be a great choice.

Climate note: If you live in a region with high ambient humidity (above 70% RH year-round), such as the Pacific Northwest, Southeast US, or coastal areas, thermowood’s lower equilibrium moisture content makes it the more reliable long-term choice. Cedar can perform well in drier climates where humidity swings are less extreme.

Thermowood vs Cedar: Which Lasts Longer?

In a well-maintained home sauna used 3-4 times per week, thermowood interiors typically last 25-30 years before requiring replacement; Western Red Cedar interiors in the same conditions average 15-20 years.

The gap widens in high-use or high-humidity environments. Cedar’s longevity depends heavily on a consistent maintenance schedule, oiling every 1-2 years for home saunas, more frequently in commercial settings. Skip that maintenance and surface checking, and gapping, warping, and eventual cracking can appear within 5-8 years in a heavily used sauna. Thermowood, by contrast, requires no oiling and holds its structural integrity through repeated wet-dry cycles because its equilibrium moisture content is already so low.

Sauna type also plays a role. In a dry sauna, cedar performs closer to its upper lifespan range because the humidity swings are less severe. In a steam sauna, the constant moisture exposure accelerates surface checking in cedar and makes thermowood’s low EMC a more decisive advantage. Alaskan Yellow Cedar is the exception among cedar species; its natural oils give it rot resistance that approaches thermowood’s, and it can reach 20-30 years in a well-maintained sauna, though at a price point that narrows the cost advantage cedar normally holds.

For outdoor saunas exposed to weather, barrel saunas, cabin saunas, or any structure without full climate control, thermowood’s Class D durability rating makes it the more dependable long-term material. Cedar will perform adequately outdoors in moderate climates but will require more frequent inspection and maintenance to reach its full lifespan potential.

The bottom line: if you’re building a sauna you want to last a generation with minimal upkeep, thermowood is the stronger investment. If you’re comfortable with a regular maintenance routine and value the traditional cedar experience, Western Red Cedar remains a proven and widely available choice.

Frequently Asked Questions

Here are the most common questions sauna builders ask when choosing between thermowood and cedar.

Can thermowood be used for outdoor saunas?

Yes. Thermowood’s low equilibrium moisture content and Class D durability rating make it well-suited for outdoor barrel saunas and cabin saunas exposed to weather. It handles freeze-thaw cycles and ambient humidity better than untreated wood, and it does not require chemical preservatives to maintain that performance.

Does thermowood smell?

Thermowood has no natural aroma. Some users add cedar accessories, such as a cedar bucket and ladle, or use essential oils to replicate the scent experience in a thermowood interior.

Is cedar or thermowood better for sauna benches?

Both work well. Thermowood aspen and alder stay cooler to the touch at high temperatures, making them preferred for bench slats where skin contact is constant. Cedar benches are comfortable but can feel warmer at the surface. Cedar’s role in traditional saunas is well established, and many builders choose it for benches specifically to capture the aromatic experience where it matters most.

How often does cedar need to be oiled in a sauna?

Typically every 1-2 years for home saunas. Commercial settings with daily use may require more frequent oiling. Skipping oiling accelerates surface checking and shortens the wood’s usable lifespan.

Can you mix thermowood and cedar in the same sauna?

Yes, and it’s a practical approach. A common configuration is thermowood for walls and ceiling cladding (where low maintenance and dimensional stability matter most) and cedar for benches (where the aromatic benefit is most noticeable during use). If you’re exploring home sauna kits that let you choose your wood, this combination gives you the best of both materials.

Is thermowood safe for saunas?

Yes. The heat treatment process is entirely chemical-free – no preservatives or adhesives are introduced at any stage. This makes thermowood safe for high-temperature, skin-contact environments, including bench slats and backrests. It is used in both residential and commercial sauna construction worldwide.

Choosing between cedar and thermowood is a tough decision since there are a lot of things to consider. Let us show you all the factors so you choose right.