Cedar vs Hemlock Sauna: Which Wood Is Better for Your Build?

Cedar vs Hemlock Sauna: Which Wood Is Better for Your Build?

For decades, cedar has been the default sauna wood in North America. Walk into most sauna showrooms and you'll smell it before you see it. But hemlock - specifically heat-treated Canadian hemlock - has been quietly taking over the market, and for good reasons that go beyond price.

If you're shopping for a sauna and trying to figure out which wood to go with, this comparison covers everything that actually matters: how they hold up, what they smell like, what they cost, and which one you'll be happier with five years from now.

The Basics: What Are We Comparing?

Western red cedar (Thuja plicata) is the classic North American sauna wood. It's naturally aromatic, naturally resistant to decay, and has been used in saunas, decks, and fences for over a century. When most people picture a sauna, they're picturing cedar.

Canadian hemlock (Tsuga canadensis) is a softwood that's been used in construction for generations but only recently became popular for saunas - specifically when heat treatment (thermowood processing) solved its biggest weakness. More on that in a minute.

Durability: Raw vs Heat-Treated

Cedar Durability

Cedar's natural durability comes from thujaplicins - organic compounds in the wood that resist rot, fungi, and insects. This is real and well-documented. A cedar sauna will hold up for 10-15 years even with regular use, and longer if well-maintained.

But cedar isn't bulletproof. Over time, the natural oils that provide that resistance deplete - especially in the high-heat, high-moisture environment of a sauna. The aromatic compounds that make cedar smell amazing are the same ones that evaporate with repeated heating. After a few years of regular use, cedar's natural rot resistance diminishes noticeably, and the famous scent fades too.

Cedar is also a relatively soft wood. It dents and marks easily, which means benches and high-traffic surfaces show wear faster. This is cosmetic, not structural, but it matters if you care about how your sauna looks over time.

Hemlock Durability (Heat-Treated)

Raw hemlock has decent strength but poor moisture resistance. That's why nobody used it for saunas historically. Heat treatment changed the game entirely.

The thermowood process heats hemlock to 400-430F in a controlled, oxygen-free environment for several days. This fundamentally changes the wood's cellular structure. The treatment removes sugars and organic compounds that attract mold, fungi, and insects. It also restructures the wood fibers to dramatically reduce moisture absorption - heat-treated hemlock absorbs about 40-50% less moisture than untreated wood.

The result is a wood that's more dimensionally stable than cedar in a sauna environment. It doesn't swell and shrink as much with the temperature and humidity cycling. It resists mold and decay not through volatile oils that eventually evaporate, but through permanent structural changes in the wood itself. The durability doesn't degrade over time the way cedar's natural oil protection does.

A heat-treated hemlock sauna, properly built, should last 20+ years of regular use.

Scent: Strong vs Subtle

Cedar has one of the most recognizable wood scents in the world. When your sauna is new, walking in is an aromatic experience - warm, resinous, and distinctly "sauna." A lot of people love it. Some people find it overpowering, especially at higher temperatures when the oils volatilize more aggressively.

Here's the thing nobody tells you in the showroom: that cedar scent fades substantially within the first 1-2 years of regular use. By year three, most cedar saunas smell like... a sauna. The wood is still cedar, but the aromatic compounds have largely evaporated.

Heat-treated hemlock has a mild, warm, almost honey-like scent - pleasant but not dominant. It won't hit you over the head when you walk in. The subtle aroma stays more consistent over time because it comes from the caramelized wood sugars created during heat treatment, not from volatile oils that evaporate away.

If a strong wood scent is important to your sauna experience, cedar delivers it up front. If you'd rather have a neutral backdrop that lets you add your own aromatherapy (eucalyptus, birch, pine essential oils), hemlock is the better canvas.

Cedar vs Hemlock Sauna: Full Comparison

Appearance: Beauty Is in the Eye of the Buyer

Cedar ranges from light amber to deep reddish-brown, often with significant color variation between boards. Some people love that natural variation. Others find it looks busy, especially in a small sauna interior where you're seeing a lot of wood grain at once. Over time, untreated cedar weathers to a silver-gray if it's exposed to sunlight.

Heat-treated hemlock has a rich, warm brown tone - sometimes described as chocolate or caramel - with a more uniform appearance board to board. The heat treatment creates a consistent color throughout the wood (not just on the surface), so scratches and wear don't reveal a different color underneath. It has a modern, clean look that works equally well in a rustic barrel sauna or a contemporary cube design.

Sustainability: A Real Consideration

This is where hemlock has a meaningful advantage. Western red cedar grows slowly - it takes 40-60 years to reach harvestable size. Old-growth cedar forests have been heavily logged throughout British Columbia and the Pacific Northwest, and supply concerns are real. Prices have climbed steadily as quality cedar becomes harder to source.

Canadian hemlock grows faster and is available from well-managed, FSC-certified forests. FSC certification means the wood is harvested sustainably - replanted, managed for biodiversity, and verified by independent auditors. You can trace FSC-certified hemlock back to the specific forest it came from.

If environmental responsibility factors into your purchasing decisions, FSC-certified hemlock is the clearer choice. Not all cedar is irresponsibly harvested, but verifying the source is harder, and the supply chain is less transparent.

Why SweatDecks Chose Heat-Treated Hemlock

When we were sourcing wood for our sauna line, we tested both extensively. We ran heat cycling tests, moisture exposure tests, and real-world use tests over months. Heat-treated Canadian hemlock won on almost every metric that matters for long-term sauna performance.

The dimensional stability means our saunas hold their shape and fit tighter over years of use. The moisture resistance means they handle loyly (steam) sessions without degrading. The consistent color means they look as good in year five as they do on day one. And the FSC certification means we can tell every customer exactly where their wood came from and how it was harvested.

Does cedar make a good sauna? Absolutely. We're not knocking it. But heat-treated hemlock makes a better one for most people, and it costs less. That combination is hard to beat.

Want to learn more about the thermowood process and why it matters? We've put together a detailed breakdown on our thermowood page.

See the Difference for Yourself

Every sauna in our outdoor collection is built with FSC-certified, heat-treated Canadian hemlock. If you want to see the raw material up close before committing to a full sauna, check out our sauna wood selection for sample options and replacement boards.

Free shipping on orders over $5,000, and every SweatDecks sauna is HSA/FSA eligible through TrueMed. Questions about wood quality or which sauna fits your setup? We're happy to walk you through it.