Cedar vs Thermowood for Outdoor Sauna Builds: Which Wood Is Right for You?

Choosing the right wood is essential to building an outdoor sauna that lasts, feels cozy, and handles your climate gracefully. Cedar and thermowood both offer strong benefits—but they differ significantly in how long they last, what upkeep they need, and how they look over time. Whether you're building in Canada’s wet west coast or freezing prairie winters, understanding these wood types helps you build smarter.

Overview of Cedar and Thermowood Properties

Cedar is a classic choice for saunas: naturally aromatic, light in weight, and rich in tannins that resist rot. Canadian Western Red Cedar, in particular, is prized for its combination of dimensional stability, low density, and pleasing grain. It releases a pleasant scent as the sauna heats, creating a sensory experience beloved by sauna enthusiasts.

On the other hand, thermowood is a softwood (often pine or spruce) that has undergone a high-temperature thermal modification process. This process removes sap and sugars, stabilizes cell structure, and improves rot and insect resistance. So what is thermowood, and how is it made? In short, it’s kiln-fired at around 200 °C in a low-oxygen environment. The result is darker, dimensionally stable wood that resists moisture and decay better than its raw counterpart.

With cedar versus thermowood sauna builds, both deliver low thermal conductivity (so they stay cool to the touch), but differing lifespan and appearance. Cedar has a richer, warmer tone and scent, while thermowood tends toward uniform brown hues and a subdued, modern aesthetic. For indoor surfaces like benches and walls, cedar is popular. For exterior cladding or temperate climates, thermowood’s enhanced durability can be a real advantage.

Longevity and Weather Resistance

One of the most important factors for outdoor saunas is how well the wood stands up to moisture cycles, UV, and freeze-thaw stress. Which is more durable outdoors?

Cedar’s reputation stems from its natural rot resistance, thanks to aromatic oils and tannins. Even untreated, cedar lasts many years—though in very wet climates, its retention of moisture can lead to surface checks or green staining over time if left unsealed. Thermowood, because it’s thermally modified, resists absorption and shrinks less, which means fewer cracks and better long-term stability.

According to timber expert Dr. Marianne Lunde: “Thermowood in outdoor applications often delivers a service life comparable to high-grade cedar, especially where incessant moisture and sun exposure are in play.” So in coastal British Columbia, Scandinavia, or interior maritimes—moist environments—thermowood may last longer with less maintenance. Meanwhile, cedar really shines in less demanding regions or for interiors where the aroma and softer wood feel matters more.

Here's a quick comparison:

Cedar excels in visual and aromatic appeal with reasonable durability. Thermowood offers superior stability and fewer checks in demanding environments—though it doesn’t smell like cedar.

Maintenance and Rot Prevention

Even durable woods need care. Knowing how to maintain cedar and thermowood keeps your sauna inviting season after season.

Cedar maintenance:

• Yearly sealing with water-repellent, UV-blocking finish extends lifespan.

• Periodic light sanding removes checks or surface grey, restoring vibrant grain.

• Moisture exposure can benefit from raised foundations or ventilated exteriors to keep siding from sitting in dirt.

Thermowood maintenance:

• Often marketed as maintenance-free, but benefits from occasional sealing in exterior exposure areas.

• Cracks can appear over time—though typically shallow and stable.

• Surface color can lighten in sun; a tinted sealant maintains the original hue if desired.

How do maintenance needs compare? Cedar requires annual sealing and occasional refinishing to maintain appearance and dimensional stability. Thermowood generally needs less sealing and fewer refinishing steps—making it lower maintenance in long-term remote usage. Both woods benefit from elevated supports, drip edges, and breathable construction to reduce rot risk.

Aesthetic Appeal: Natural vs Processed Look

When stepping into a cedar sauna compared to a thermowood one, the differences in visual and tactile experience are clear.

Cedar’s aesthetic:

• Warm reddish-brown tones that age gracefully to pale silver if unsealed.

• Grain patterns visible through oils, with aromatic oils that release under heat.

• Color variation within staves contributes to rustic charm.

• The scent of cedar enhances the sauna ritual.

Thermowood’s aesthetic:

• Even brown to chocolate tones with no scent.

• Smooth texture and consistent density resulting from the processing.

• Ideal for modern, minimalist sauna interiors or exteriors.

• Metallic glares diminish over time to a soft grayish patina if left outside.

Which wood looks best? Cedar appeals to those wanting a classic sauna vibe—organic, rich, and aromatic. Thermowood is visually striking in its uniformity and depth—perfect for clean, modern cabins or where scent is unwanted (like allergy-sensitive users). Blending both (cedar interior, thermowood exterior) is a popular hybrid in many builds.

Cost Comparison and Availability in Canada 

In Canada, availability and price can vary significantly between cedar and thermowood.

Cedar pricing:

• Widely available in Canada, particularly Western Red Cedar.

• Expect premium prices per board foot—especially in high-quality clear grade.

• Shipping costs are low within British Columbia or Ontario where mills exist.

Thermowood pricing:

• Imported or produced regionally, price varies based on species.

• Often priced lower per square foot than clear cedar, especially for exterior siding.

• Import logistics to remote regions may add cost—but thermowood still offers value for large builds.

What about pricing and availability across Canada? Cedar remains more accessible and renowned, especially in western provinces. Thermowood is gaining traction, particularly where mills process spruce or pine in northern Ontario and Quebec. For large builds like a full sauna shell or siding, thermowood can save hundreds—or even thousands—over cedar. On the other hand, cedar continues to command premium pricing for indoor surfaces or benching due to its scent and softness.

A builder in British Columbia recently shared, “We chose cedar for the interior benches but thermowood for the exterior siding—it cut our costs and weathered the coastal storms like a champ.” Many Canadian sauna builders follow this hybrid strategy: interior cedar for atmosphere, exterior thermowood for durability and economy.

When to Choose Which: Quick Decision Guide

Use this guideline to decide which wood fits your needs:

• Rainy or maritime coast? Thermowood’s stability and reduced water absorption make it ideal.

• Northern or prairie freeze-thaw cycles? Thermowood ages more evenly with less checking.

• You want cedar aroma and classic looks? Use cedar inside; consider thermowood outside.

• Working with a tight budget on large builds? Thermowood can yield significant material savings.

• Want low long-term maintenance? Thermowood requires less refinishing overall.

• Prefer the soft feel of wood under bare feet? Cedar’s softness makes it a preferred bench surface.

• Concerned about allergies or scent? Thermowood is scent-neutral.

Both wood types offer excellent performance for sauna builders who design wisely and plan maintenance. Whether you lean toward cedar’s aromatic warmth or thermowood’s enduring resilience, making the right choice for your climate, budget, and needs sets you up for years of cozy, low-maintenance soaking.

Want to explore cedar or thermowood sauna kits? Browse our collection of clear cedar saunas and thermowood models to compare species, sizing, and price. We offer design support to match the right wood to your climate and style.

With proper selection and upkeep, you'll enjoy a beautiful, efficient sauna retreat that survives seasons—and perhaps even generations. Choose your wood wisely, and your sauna becomes more than a build—it becomes a legacy of warmth, comfort, and craft.