Why Are Saunas Made Of Wood? Heat, Safety, & Comfort Guide

It is kind of wild when you think why are saunas made of wood. We use metal for heat, tile for water, plastic for just about everything else. But saunas? All wood, all the way. Almost like there is an unspoken rule: If it is not wood, it is not a sauna.

This isn’t some happy accident. There is a reason every legit sauna smells like a forest and not a hardware store. And once you notice it, you can’t unsee it. That is what we are breaking down in this article – the heat dynamics, safety perks, and that unexpected comfort factor that only wood brings to the table (or bench, in this case).

Why Are Saunas Made Of Wood? All You Need To Know In A Minute

• Wood stays touch-safe even at 180°F, unlike metal or tile, which can burn skin instantly.
• It absorbs steam and lets it out gradually, keeping air balanced without puddles or dry patches.
• Cedar, ThermoWood, and similar timbers block mold, mildew, and bacteria without chemical coatings.
• Wood insulates heat evenly, so your sauna warms up fast without hot spots or temperature swings.
• It softens noise, holds scent, and feels warm under bare skin, which makes the entire space feel human-friendly.

Why Are Saunas Made Of Wood & What Makes It Safer?

Wood is the go-to material for saunas because it handles heat better than anything else. It doesn’t overheat, doesn’t burn skin, and helps create the calm, even warmth saunas are known for. It also absorbs moisture without warping and feels natural to the touch, which is key to both comfort and safety.

What makes it safer:

• Doesn’t conduct heat like metal or tile, so surfaces stay skin-safe
• Expands and contracts gradually without cracking under heat shifts
• Insulates heat evenly, so the sauna warms up without hotspots
• Doesn't release harmful fumes, unlike some treated composites
• Supports steady humidity without trapping excess moisture

Why Are Saunas Made Of Wood? 7 Reasons That Make It the Best Choice

Review these 7 reasons to understand what wood can actually handle and why it works.

1. Heat Tolerance Without Overheating

Wood doesn’t trap heat like tile, metal, or plastic. It slows heat transfer so you can lean back without burning your skin. That’s because woods like cedar and aspen have low thermal conductivity, even at 180°F. The result is an even warmth, fewer hot spots, and no sharp temperature spikes.

2. Moisture Resistance & Mold Prevention

Unlike porous synthetics or soft, untreated woods, sauna-grade timber pulls in and releases moisture without rotting. Cedar and ThermoWood go a step further as they resist mold, bacteria, and mildew. High-traffic spas stick with it because of less risk, longer life, and better hygiene.

3. Structural Stability In Extreme Conditions

Slow-grown Nordic wood has tighter grain and fewer knots, which means fewer cracks or splits when temperatures jump. Thermally modified woods also stay dimensionally stable after years of use. Even in outdoor saunas, this stability means less warping and better joint integrity over time.

4. Hygroscopic Balance For Optimal Humidity

Sauna wood breathes. It absorbs steam and releases it gradually to regulate the cabin’s humidity. That keeps the air comfortably moist without soaking the walls or leaving puddles. Your skin feels the difference after just 1 session.

5. Aromatherapeutic Benefits

Heat brings out the essential oils locked inside woods like cedar, spruce, and pine. These natural scents calm the nervous system and help the brain shift into parasympathetic mode. It’s not just ambiance; it’s part of the recovery process.

6. Thermal Insulation For Energy Efficiency

Wood holds heat but doesn’t trap it in the way stone or synthetic panels might. That cuts down the time and power it takes to keep your sauna at full temperature. Whether you use a wood stove or an electric heater, wood lowers your running costs without compromising performance.

7. Natural Texture = Built-In Comfort

Wood feels soft and forgiving under the skin, even when dry. There’s no sting, no chill, and no hard glare. That tactile warmth is why high-end saunas never use metal or acrylic on the interior walls or benches.

7 Benefits Of Wood In Sauna Construction

Read these 7 wood-specific perks to see how they shape how your sauna feels, sounds, and ages.

1. No Flinch Factor

Wood doesn’t burn skin, even when the cabin hits full temperature. You can lean back, lie down, or shift positions without fear of stinging heat. It stays comfortable at every touchpoint, including benches, walls, and backrests.

2. Your Sauna Smells Like Nature, Not Plastic

Heated cedar, spruce, and pine release essential oils that calm your nerves and cue your body to relax. These scents don’t feel artificial or overwhelming—they feel real. It's built-in aromatherapy without needing oils or sprays.

3. Warmth That Looks The Part

The natural tones and grain of sauna wood create that spa-like feel you expect. Wood softens shadows, glows under low light, and instantly makes a space feel calm and complete. No gloss. No glare. Just warmth.

4. Gets Better With Age

Some materials crack, peel, or turn yellow over time. Thermo-treated woods like Thermo Aspen only deepen in tone and texture. They build character instead of flaws, and your sauna keeps its premium feel without effort.

5. Quiet That Feels Intentional

Wood absorbs noise. It doesn’t echo like tile or bounce sound like glass. That softness shapes the whole vibe with no clatter and no sharp acoustics, just silence that helps you reset.

6. Feels Like It’s Made For Humans

Plastic feels fake. Metal feels cold. Wood just feels right. It’s easy on bare feet, soft under your back, and never shocks you with temperature swings. That trust in the surface helps your body let go.

7. Looks Like It Belongs Outdoors

Wood connects your sauna to its natural setting. Whether it's tucked in a backyard or next to a lake, it blends in and doesn’t stick out. That visual comfort matters because your brain reads it as a place to rest, not perform.

6 Common Types Of Wood Used In Saunas & Why

Use this section to match the right timber to your budget, usage style, and design needs.

1. Choose Cedar If You Want Performance That Smells Like Luxury

Cedar holds up in high heat, smells incredible, and naturally blocks mold and mildew. Whether you go for Western Red or Knotty Cedar, it performs beautifully for decades.

Pros of using cedar in your sauna:

• Fights mold and bacteria without chemical treatment
• Withstands years of heat and humidity without warping
• Smells clean and earthy, even after dozens of sessions
• Insulates well and heats evenly
• Ages beautifully instead of fading

Cons of using cedar in your sauna:

• Higher cost than most sauna woods
• Color can darken over time
• It may be too aromatic for those with scent sensitivities

Best for:

• Outdoor or high-humidity sauna setups
• Anyone who values scent, durability, and aesthetics

Avoid if:

• You need a budget-friendly option
• You’re highly sensitive to strong natural aromas
• You want a very light interior finish

Common bench pairing: Cedar on benches adds warmth and scent, but some mix it with aspen for a lighter visual balance.

2. Go With Aspen For A Light, Hypoallergenic Finish

Aspen has a clean, pale look and doesn’t release resin or aroma, which makes it ideal for scent-sensitive users or spa-style interiors.

Pros of using aspen in your sauna:

• Hypoallergenic and resin-free
• Cool to the touch, even at high temperatures
• Naturally smooth with minimal knots
• Affordable compared to cedar
• Light tone brightens compact spaces

Cons of using aspen in your sauna:

• Not as durable as cedar
• Can dent more easily if untreated
• Needs thermal treatment for outdoor use

Best for:

• Indoor saunas and light design schemes
• Users with allergies or asthma
• Clean, modern aesthetics

Avoid if:

• You’re placing the sauna outdoors
• You want a strong aroma or color contrast
• You plan heavy use in public/commercial settings

Pairing tip: Use aspen for interior walls and mix with alder or ThermoWood for benches to boost strength.

3. Pick Alder For Warmth Without Maintenance Headaches

Alder’s reddish hue adds visual warmth without the need for much upkeep. It resists cracking and works well as an accent or primary interior wood.

Pros of using alder in your sauna:

• Withstands heat without warping
• Low maintenance and long-lasting
• Visually warmer than aspen but still subtle
• Can be thermally modified for added stability
• Works well with LED or dim lighting setups

Cons of using alder in your sauna:

• Not as fragrant as cedar
• Slightly softer than ThermoWood
• May vary in tone depending on the source

Best for:

• Mixed interiors (e.g., aspen + alder)
• Cozy, natural-toned design styles
• Those who want warmth without scent

Avoid if:

• You want strong essential oil scents
• You expect rough use or high foot traffic
• You prefer light or white-toned interiors

Expert tip: Thermo-treated alder deepens in tone and lasts longer with less shrinkage.

4. Choose Hemlock For Clean Lines Without The Smell

Hemlock is a knot-free, scent-free option that’s surprisingly durable for the price. Great for those who want simplicity, silence, and affordability.

Pros of using hemlock in your sauna:

• Doesn’t release strong scents
• Uniform texture and light color
• Low shrinkage and good longevity
• Works well for cladding or full interiors
• Lower cost than cedar or ThermoWood

Cons of using hemlock in your sauna:

• Less character than cedar or alder
• It can dry out if not sealed properly
• Not naturally antimicrobial

Best for:

• Infrared saunas and scent-sensitive homes
• Minimalist or Scandinavian-style interiors
• Homeowners who want long-term value

Avoid if:

• You want scent or antimicrobial benefits
• You’re building an outdoor sauna without treatment
• You plan to expose it to daily high humidity

Ideal placement: Works best in indoor saunas or covered outdoor models with stable humidity.

5. Use ThermoWood If You Want Set-And-Forget Stability

Thermally modified woods like Thermo Aspen or Thermo Spruce go through a high-heat, steam-based process that strengthens them from the inside out.

Pros of using ThermoWood in your sauna:

• Enhanced moisture resistance
• No resin or chemical off-gassing
• Color darkens naturally over time
• Long lifespan, even with heavy use
• Doesn’t swell or warp with seasonal shifts

Cons of using ThermoWood in your sauna:

• Slightly more expensive than untreated options
• Color darkens (which may not suit all aesthetics)
• The surface can feel drier or more brittle without oiling

Best for:

• Outdoor saunas or coastal environments
• High-traffic commercial or wellness studio setups
• Owners who want ultra-low maintenance

Avoid if:

• You prefer bright or pale sauna interiors
• You want a wood that releases a strong aroma
• You’re building on a tight budget

Durability rating: Often lasts 25+ years with minimal treatment.

6. Try Spruce If You Want Tradition Without The Price Tag

Spruce is the classic sauna wood in Finland. It’s easy to source, lightweight, and budget-friendly, but it does need extra prep for long life.

Pros of using spruce in your sauna:

• Clean grain and soft tone
• Excellent thermal insulation
• Widely available and affordable
• Pairs well with Thermo-treated options
• Great for walls and ceiling cladding

Cons of using spruce in your sauna:

• Can leak resin if not heat-treated
• Slightly more knotty than aspen or hemlock
• Not naturally resistant to mold

Best for:

• Budget-conscious builds
• Indoor saunas or partial applications
• First-time sauna owners

Avoid if:

• You need maximum durability outdoors
• You want a high-end finish
• You don’t like knot marks or yellowing

Finishing tip: Use Thermo-Spruce instead for extra moisture protection.

Do Saunas Have To Be Made Of Wood? Comparing The 4 Alternatives You Can Try

Saunas don’t have to be made of wood, but the moment you trade it out, you give something up. Wood isn’t just tradition. It solves for heat, safety, comfort, and acoustics in ways that materials like stone, glass, or metal can’t match.

Compare how these 4 materials perform compared to wood in real sauna conditions before you decide:

Do Wooden Saunas Get Moldy Or Rot Over Time? 5 Preventative Measures You Need To Know

Wooden saunas only rot or grow mold if you neglect them. When built with the right wood and kept well-ventilated, they can stay mold-free for decades. Most mold issues come down to poor airflow, trapped humidity, or untreated materials.

Use these 5 preventative measures that actually work:

• Ventilate after every session: Open the door for at least 30 minutes post-use to release trapped moisture. For indoor models, install a vent near the floor and one near the ceiling to create passive airflow.
• Use thermally modified or antimicrobial wood: ThermoWood, cedar, and hemlock naturally resist fungal growth. Avoid untreated pine or low-density softwoods in high-humidity zones.
• Seal critical zones with breathable oils: Apply a sauna-safe oil (like paraffin-free linseed) every 3–6 months to high-contact areas like benches and backrests. Don’t seal entire walls; you need to let them breathe.
• Clean wood monthly with pH-neutral sauna cleaner: Use a soft brush or cloth and a diluted natural cleaner like baking soda and water or a wood-safe citrus formula. Never use bleach or harsh chemicals, as they strip the wood and increase cracking.
• Dry it out weekly: If your sauna is used often, run a dry heat cycle (with no steam or humidity) for 20–30 minutes once a week to reset internal moisture levels and prevent spore growth.

7 Steps To Choose The Right Sauna Wood For Your Needs

Use this checklist to match the right wood to your space, climate, habits, and preferences.

Step 1: Check How Sensitive You Are To Smells

Some sauna woods give off strong scents when heated. Others stay neutral. That difference can make or break your session comfort.

• Go for cedar, spruce, or pine if you love earthy or smoky aromas.
• Pick aspen or hemlock if strong scents trigger headaches or asthma.
• Avoid aromatic woods if you have sinus issues, even mild ones.
• Step into a heated cedar sauna at a spa first to test your response.
• Test with everyone who plans to use it if you share the sauna.

Step 2: Lock In Indoor vs Outdoor Placement

Sauna wood behaves differently based on exposure to wind, moisture, and UV. What works inside may fail outside.

• Stick to ThermoWood, cedar, or other weather-hardened timber for outdoor builds.
• You can use lighter, untreated woods like aspen or alder for indoors.
• Always choose woods that won’t swell or rot in humid regions
• Consider adding a roof overhang or enclosure to shield exterior walls.
• Ask for moisture rating data if you’re buying pre-cut panels.

Step 3: Know Your Budget & Long-Term Maintenance Limit

You don’t just pay once. Some woods save you money upfront, but need more repairs. Others cost more now but last 25+ years.

• Set a realistic budget range: $5–$15 per sq. ft. for panel wood.
• Cedar, ThermoWood, and premium alder cost more but save on sealing and repair.
• Hemlock and spruce are cheaper but may need replacement sooner.
• Check local availability; imported woods often spike in price.
• Factor in treatment, oiling, and cleaning costs over 5–10 years.

Step 4: Match Your Style: Natural, Rustic, Or Sleek

Some woods feel rugged. Others look modern or spa-like. Pick one that makes you want to use your sauna daily.

• Aspen offers a pale, modern feel that brightens tight spaces.
• Cedar and alder bring visual warmth for cozy, lodge-style vibes.
• Hemlock and spruce work well in minimalist or Scandinavian designs.
• Use mixed wood schemes to balance light and dark tones.
• Try samples under your sauna lighting to preview the full effect.

Step 5: Choose The Right Wood For Each Sauna Zone

Not all parts of the sauna face the same pressure. The wood that works for the ceiling won’t always hold up on a bench.

• Use resin-free, low-splinter woods like aspen or ThermoWood for benches.
• Pick heat-resistant, insulating woods like cedar or spruce for walls and ceilings.
• Opt for slatted designs and use woods with anti-slip texture for floors.
• Use high-resistance wood in heat shield zones behind heaters.
• Ask your supplier if wood has been kiln-dried or heat-treated for your climate.

Step 6: Consider The Climate You Live In

Your environment affects how sauna wood ages. Some woods crack in dry air. Others swell in tropical zones.

• Use slow-grown Nordic timber with tight grain in cold, dry regions.
• Pick Thermo-treated woods with sealed ends in coastal or rainy zones.
• Avoid untreated pine in damp areas, as it molds fast.
• Track indoor humidity with a hygrometer (aim for 10–20% between sessions).
• Store spare boards indoors to keep replacements climate-stable.

Step 7: Don’t Just Match, Test First

Photos and reviews can’t replace real use. Sit on it. Smell it. Run your hand across it.

• Order wood samples and test them in a heated room.
• Wet the surface to see how grain and color change with humidity.
• If possible, visit a spa that uses your top 2 options.
• If unsure between 2 types, combine them: walls vs. benches.
• Always pick what your skin, nose, and eyes agree on together.

Conclusion

Some decisions in sauna design are negotiable, but “why are saunas made of wood?” isn’t one of them. From thermal comfort to skin safety and long-term resilience, wood simply does what other materials can’t. It doesn’t just perform better, it feels better, smells better, and lasts longer when chosen with care.

That’s why Nordvik builds every sauna around real wood instead of trends. It’s about longevity, balance, and giving your body the kind of space it can actually settle into. From the rounded warmth of a barrel sauna, to the clean lines of a cube, to the wide-open views of a panorama model—each design is built to serve a purpose and stand the test of time.

FAQs

How long does sauna wood last?

High-quality sauna wood can last 15 to 30 years with proper ventilation and care. ThermoWood and cedar often push past the 25-year mark, especially in dry, well-maintained setups.

Why are some sauna woods more expensive than others?

Price comes down to density, rarity, thermal treatment, and longevity. Cedar, for example, costs more due to its natural resistance to decay and its high durability in humid heat.

What happens if I use untreated wood in my sauna?

Untreated wood swells, cracks, and traps moisture faster. It’s also more prone to mold and may release resin or splinters under heat, none of which you want inside your sauna.

Can I use the same wood for benches, walls, and ceilings?

You can, but it’s not ideal. Benches need smooth, resin-free wood that won’t splinter. Walls and ceilings benefit from insulating woods that don’t warp or leak sap.