Cedar vs. Hemlock vs. Thermo-Spruce: Which Sauna Wood Is Right for You?

Why Sauna Wood Matters More Than You Think

The right sauna wood doesn't come down to which species sounds most premium. It depends on the type of sauna you're buying, where you plan to install it, and how you'll use it.

Most online comparisons cover only cedar versus hemlock, leaving buyers who encounter brands like SaunaLife or Thermory wondering what "thermo-spruce" actually means. That's a gap worth filling, especially as thermally modified wood gains ground in premium sauna construction.

This guide is a practical, fact-checked comparison that maps each wood type to real buyer scenarios: indoor versus outdoor, infrared versus traditional versus barrel. We won't make unsupported claims about lifespan or heat retention. We'll stick to what manufacturers confirm and what the research actually shows.

Cedar: The Classic North American Sauna Wood

Western red cedar is the most recognized sauna wood in North America and has been the traditional standard for premium builds for decades. If you picture a classic outdoor sauna, you're probably picturing cedar.

What makes cedar distinct is its natural oil content. Cedar contains oils called thujaplicins that provide built-in antimicrobial protection and inherent water resistance without any applied coatings, according to Sun Home Saunas. Hemlock and untreated spruce don't share this property.

Visually, cedar has a warm reddish-brown tone with a straight grain that many buyers find familiar and inviting. Its distinctive aroma comes from terpenes, including cedrol and α-cedrene. Most people find this scent pleasant, but individuals with terpene sensitivities or allergies may find it irritating, as noted by Peak Primal Wellness.

Cedar is particularly well-suited to outdoor installations, where its natural rot resistance is most valuable against weather and moisture exposure. That durability does come at a cost: cedar commands roughly 30–50% more than hemlock, making it a long-term investment consideration rather than a drawback.

Dundalk Leisurecraft, an authorized brand we carry at Sauna Luxuries, uses Eastern White Cedar as its primary construction material for barrel and cabin sauna kits, as confirmed on their product pages and by Haven of Heat.

One important care note: cedar interior surfaces should never be stained, varnished, or painted. According to Finnleo and Sauna Supply Co., coatings trap moisture, can cause warping or cracking, and may produce fumes when heated. The wood must breathe.

Hemlock: The Reliable Choice for Indoor Infrared Saunas

Canadian hemlock (Tsuga canadensis) is the dominant wood used in mid-range infrared sauna cabinets. Brands such as Dynamic Saunas, Golden Designs, and Maxxus commonly build with hemlock.

Hemlock has a pale cream color with a fine grain, giving it a clean, neutral aesthetic. It works well in modern interiors where a subtle, understated look is preferred over cedar's bolder reddish-brown tones.

While hemlock lacks cedar's natural antimicrobial oils, it offers excellent dimensional stability and resists warping and splitting well. In indoor, climate-controlled environments where infrared saunas typically operate (lower temperatures, no steam, no weather exposure), this trade-off works in hemlock's favor.

One genuine advantage hemlock holds: it's a low-scent wood. For buyers with terpene sensitivities or allergies, or anyone who prefers to control their aromatherapy experience with essential oils, hemlock provides a neutral canvas. This is an underserved but growing buyer segment.

Hemlock is typically the most affordable of the three woods discussed here, making it accessible for buyers focused on value without sacrificing quality in an indoor setting.

The same care principle applies: hemlock interiors should not be stained, sealed, or painted. Let the wood breathe.

Thermo-Spruce: What It Is and Why It's Different

Here's the clarification most comparison articles miss: thermo-spruce is not a separate wood species. It is ordinary spruce (typically Nordic spruce, Picea abies) that has been thermally modified using only heat and steam at approximately 180–220°C (356–428°F) in the absence of oxygen, as documented by Saunest and Lunawood.

Why does this matter? Untreated spruce bleeds sticky resin at sauna temperatures, making it unsuitable for sauna interiors without modification. The thermal process changes the wood's cellular structure, eliminating resins entirely while improving stability and moisture resistance, as confirmed by Haven of Heat.

Crucially, the process uses no chemical agents — heat and steam only. Peer-reviewed research published in NCBI/PMC confirms this is an environmentally friendly modification method, which matters for eco-conscious buyers who consider sustainability a purchase driver.

Thermo-spruce has a distinctive appearance: a rich golden-brown or amber color with visible knotty grain. It reads as a rustic Nordic aesthetic, clearly different from hemlock's pale cream and cedar's reddish-brown. For buyers furnishing modern or Scandinavian-style homes, this look is a genuine draw.

SaunaLife, an authorized brand we carry at Sauna Luxuries, uses thermally modified Nordic spruce for exterior construction across most of its barrel, cube, and cabin models, paired with thermo-aspen for interior benches and backrests. The SaunaLife ERGO barrel series (E6, E7, E8) uses 1.65-inch-thick full-length thermo-spruce staves, as confirmed on product pages documented by Sauna Marketplace. Thermory is another high-end European manufacturer that uses thermally modified Nordic spruce for barrel sauna construction.

Laboratory research published in NCBI/PMC confirms that wood thermally modified at and above 200°C shows better resistance to brown-rot fungus (Serpula lacrymans) than untreated spruce. That's a verified finding from controlled decomposition tests, not a marketing claim.

The Mixed-Wood Reality: How Premium Saunas Actually Use Multiple Species

Premium manufacturers often use different woods for different parts of the same sauna. Exterior cladding, interior walls, and benches may each use a different species optimized for that specific zone.

SaunaLife is a clear example. Their barrel saunas use thermo-spruce for the exterior structure, paired with thermo-aspen for interior benches and backrests. Finnleo takes a similar zone-based approach: Nordic white spruce for interior walls and ceilings, with exteriors built from either clear western red cedar or heat-treated Canadian hemlock.

This isn't a quality compromise. It reflects deliberate engineering choices that match each wood's properties to the demands of each zone. If you see two or three wood types listed on a product page, that's normal and intentional, not inconsistent.

It's also worth noting that for outdoor sauna exteriors, wood species alone doesn't guarantee durability. Roof overhangs, flashing, drainage, a raised base, and proper ventilation are equally important factors, as highlighted by Marterra Elements.

Choosing the Right Wood for Your Sauna: A Simple Buyer Guide

No single wood is universally superior. The right choice depends on your specific situation.

• Cedar is your match if you're buying an outdoor traditional or barrel sauna, want natural rot resistance and a classic aesthetic, and enjoy (or at least don't mind) cedar's aromatic scent.
• Hemlock fits best for indoor infrared sauna buyers who prioritize affordability, a scent-free environment, and solid dimensional stability in a controlled indoor setting.
• Thermo-spruce is the choice for buyers drawn to European barrel or cabin models, the Nordic golden-brown aesthetic, or eco-conscious sourcing with a chemical-free modification process.

If you're scent-sensitive, both hemlock and thermo-spruce are low-scent alternatives to cedar. This is a meaningful differentiator that's often overlooked.

It's also worth recognizing that infrared sauna buyers and traditional or barrel sauna buyers have genuinely different wood needs. Hemlock dominates infrared cabinets (lower temperatures, indoor use, no steam), while cedar and thermo-spruce dominate traditional and barrel formats (higher temperatures, steam, outdoor exposure).

Quick Comparison Table

Wood Type	Appearance	Natural Oils	Best For	Scent Level	Typical Sauna Format
Western Red Cedar	Reddish-brown, straight grain	Yes (thujaplicins)	Outdoor traditional & barrel saunas	Aromatic (terpenes)	Barrel, cabin, outdoor kits
Canadian Hemlock	Pale cream, fine grain	No	Indoor infrared saunas	Low / neutral	Infrared cabinets
Thermo-Spruce	Golden-brown / amber, knotty grain	No (resins removed)	Outdoor barrel & cabin saunas, eco-conscious buyers	Low / neutral	Barrel, cube, cabin (European brands)

Buyer Checklist

1. Will the sauna be indoors or outdoors? Outdoor installations benefit from cedar's natural rot resistance or thermo-spruce's modified durability. Indoor infrared saunas pair naturally with hemlock.
2. Do you have scent sensitivities? If yes, hemlock or thermo-spruce will serve you better than cedar.
3. Are you drawn to a specific aesthetic? Classic reddish-brown (cedar), clean and neutral (hemlock), or rustic Nordic amber (thermo-spruce)?
4. What brand and model are you considering? The model often determines the wood. Dundalk Leisurecraft builds with Eastern White Cedar. SaunaLife builds with thermo-spruce and thermo-aspen. Infrared brands like Dynamic Saunas and Golden Designs use hemlock.

We carry authorized brands including Dundalk Leisurecraft (cedar) and SaunaLife (thermo-spruce) at Sauna Luxuries. Our sauna specialists can help match the right model to your preferences, space, and climate. That guidance is part of the lifetime expert support included with every purchase.

Final Thoughts: Let the Model Guide the Wood Choice

The best sauna wood is the one that matches your specific model, climate, and personal preferences, not the one that sounds most premium on paper.

All three woods covered here are used in high-quality saunas by reputable manufacturers, each for good reasons. When evaluating a sauna purchase, look at confirmed product specifications rather than general claims. The manufacturer's product page will tell you exactly what wood is used and where.

If you'd like help sorting through wood types, model options, or what fits your space, our founder Reid Hollis and the Sauna Luxuries team are available to walk you through it. No pressure, no rush. Just clear answers from someone who knows the products inside and out. That's what our lifetime expert support and white-glove service are built for.

Care and maintenance advice in this article is based on manufacturer documentation from Finnleo, Sauna Supply Co., and Thermory. All wood type claims are verified against manufacturer product pages.

Sources

• Sun Home Saunas — Cedar vs Hemlock Sauna
• Peak Primal Wellness — Best Wood for a Sauna
• Haven of Heat — Best Sauna Wood Types
• Finnleo — Tips for Cleaning and Maintaining Your Sauna
• Sauna Supply Co. — How to Treat & Protect Sauna Wood
• Saunest — The Benefits of Thermo-Spruce in Sauna Construction
• Lunawood — Why Thermowood is the Best Wood for Saunas
• Haven of Heat — Thermo-Spruce Sauna Wood
• NCBI/PMC — Impact of Thermal Treatment and Aging on Lignin Properties in Spruce Wood
• Sauna Marketplace — Barrel Sauna Wood Types
• NCBI/PMC — Changes in Chemical Structure of Thermally Modified Spruce Wood Due to Decaying Fungi
• Marterra Elements — Sauna Wood Types Explained