There’s nothing quite like stepping into a sauna when the world outside is frozen solid—the air sharp, the snow piled high, and the heat wrapping around you like a second skin. But for that comfort to last year after year, the sauna itself has to be built for battle. Canada’s climate doesn’t forgive weakness.
One season brings relentless heatwaves; the next, your sauna is buried beneath ice and snow. Those wild temperature swings test every joint, every plank, every seal. And while cedar remains one of the most beautiful and aromatic woods you can build with—it isn’t indestructible.
The Cedar Dilemma
Let’s talk about cedar. It’s the go-to wood for most outdoor saunas across North America. Easy to source, gorgeous grain, that signature sauna scent—there’s a lot to love.
But here’s the part few people talk about: cedar moves. When it gets cold, it contracts. When it’s hot, it expands. Multiply that by 365 days a year, and the result is warping, shrinking, and cracks that show up just when you thought your sauna was “broken in.”
That’s not a design flaw. It’s just what natural wood does when it’s exposed to Canadian extremes.
Now, if you’re okay with some seasonal maintenance—oiling, tightening, maybe sanding—cedar can still be a solid choice. But if you’re looking for longevity, there’s something better.
Enter Thermo-Wood
Thermally modified wood—often called ThermoWood—is a game-changer. The wood is treated with heat and steam at temperatures over 180°C, altering its structure at the cellular level.
What that means in plain terms: it doesn’t absorb water like untreated wood does. It doesn’t swell, crack, or warp with the seasons. It stays stable.
For sauna builders, that’s a big deal. Because while a traditional cedar sauna may need touch-ups and replacements after a few years outdoors, a ThermoWood sauna keeps its shape and integrity for decades. It also naturally resists decay and rot, which means less upkeep, fewer surprises, and more time actually enjoying the heat instead of maintaining it.
Insulation and Airflow Matter
A sauna built for the Okanagan Valley will face very different challenges than one sitting lakeside in northern Alberta. Wherever it stands, insulation is your unsung hero.
Think of insulation as your sauna’s winter coat—it keeps the heat in and the cold out. The most efficient setups use insulation behind the walls, sealed properly to prevent moisture buildup.
That said, not every sauna relies on insulation. Barrel saunas, for example, are often built without it. Their rounded shape naturally promotes air circulation, and when built with ThermoWood, they hold heat far more efficiently than most expect.
One of the hidden advantages of thermally modified wood is its ability to reflect and retain heat. Because of the heat treatment process, ThermoWood’s cell structure becomes denser and less porous. Instead of absorbing heat like raw wood, it reflects it back into the sauna space—almost like a natural thermal shield.
That’s why ThermoWood is an ideal choice for outdoor barrel saunas. Even without added insulation, it creates a consistent, comfortable heat while maintaining energy efficiency. You’ll reach your desired temperature faster, and the sauna will hold it longer—using less energy overall.
So while insulation plays a key role in most sauna builds, the material itself can sometimes be the insulation. When engineered correctly, ThermoWood does both the job of the structure and the shell that protects it from Canada’s wild weather.
But don’t stop there. Ventilation is just as important. Without proper airflow, humidity collects, condensation forms, and before long, wood starts to deteriorate. A well-placed intake near the heater and an exhaust near the ceiling can make the difference between a sauna that lasts 5 years and one that lasts 25.
Foundation and Finishing Touches
Even the best materials fail if the foundation isn’t solid. Outdoor saunas need proper drainage and airflow beneath them—especially if they sit on a deck or concrete pad. Trapped moisture is the silent killer of wood structures.
Then there’s the finish. If you’re building with cedar, a UV-protective oil is essential to slow fading and surface wear. For ThermoWood, a clear oil can enhance its natural deep tone without the need for frequent reapplication.
Small details—like stainless steel fasteners and weather-sealed doors—also make a big difference in longevity. Every screw and hinge matters more than you think when temperatures swing 80 degrees over the course of a year.
Built to Endure
At Inland Sauna, we build with one thing in mind: permanence. A sauna isn’t just another backyard project—it’s a legacy. It should be something your family enjoys year after year, through snowfalls, heatwaves, and everything in between.
If you want to build a sauna that lasts in Canadian winters, focus on three things: the right materials, the right insulation, and the right airflow.
That’s how you build something that feels like nature—and lasts against it.