Sauna wood: Canadian red cedar inside, heat-treated outside

Everyone has a reason to sit in the heat.

Which one is yours?

After workThe heat on. The day switched off.
After trainingStraight from the run, the ride or the gym.
Hot and coldRounds between the sauna and the ice bath.
With friendsRoom for a few. Time to talk.
Before bedA slow, warm end to the day.
The ritualThe same time, the same place, most days.

Whatever your reason, one thing is the same for everyone.

You touch the wood. You smell it. You breathe it.

So the wood matters a lot.

We make ice baths from stainless steel, with no wood in them. Sozen make saunas. They make them better than we could.

So we teamed up with them. Now you get a sauna you can trust. It sits beside an ice bath you can trust.

Here is what their wood does, step by step.

The journey, step by step

01The smell of real cedarWhen you open the door
02Cool to the touchWhen you sit down
03Warm sooner, warm for longerWhen the heat rises
04Made for sun and rainThe outside walls
05Built to lastThe years after
06Your saunaWith an ice bath beside it

01 · Opening the door

The smell of real cedar

You open the door.

The first thing you notice is the smell.

That smell is Canadian red cedar. Sozen leave it natural. Nothing is painted or sprayed on it.

Cedar has its own oils. They keep rot and bugs away. So the wood needs nothing on it. The smell stays.

Sozen only use the top grade of cedar. It has no knots. Knots can get hot. They can leak sticky sap.

This top grade costs about twice as much.

The grade

What red cedar costs, a square foot

Clear$8–12 · no knots · in a Sozen sauna

Knotty$4–6 · knots that run hot and can leak resin

On average twice the price

Tahoe Sauna Company, Western red cedar for saunas, June 2026

Inside a finished sauna: clear cedar walls, ceiling and benches, lit under the benches — Top-grade Canadian red cedar inside a Sozen sauna.

02 · Sitting down

Cool to the touch

You sit down. The air is 80–90°C.

Canadian red cedar stays cooler to the touch.

It is a light wood. It is about 40% lighter than sungkai. Sungkai is a wood many saunas in Indonesia use inside.

Light wood feels cooler on your skin.

Weight

A cubic metre, dried

Lighter is better: cooler to touch

Red cedar380 kg

SungkaiAbout 640 kg

About 40% lighter

Queensland Government; Forests, 2023

03 · The heat

Warm sooner, warm for longer

You pour water on the hot stones. Steam fills the room.

Cedar walls hold the heat in. They hold it about 65% better than sungkai walls. Sozen make the walls 40 mm thick.

So the room gets warm sooner. The heater does less work. It costs less to run.

Insulation

How well a 40 mm wall keeps the heat in

Higher is better: costs less to run

Red cedarAbout 0.41 m²·K/W

SungkaiAbout 0.25 m²·K/W

About 65% better

Worked out from the USDA Wood Handbook, 2021: 40 mm divided by how well each wood conducts heat at 12% moisture

04 · Outside

Made for sun and rain

You step outside between rounds. You look back at the sauna.

The outside is not cedar. It gets sun and rain every day. So it needs a tougher wood.

Sozen use mahogany. They bake it in a special oven. All the air is taken out of the oven first.

With no air, the wood cannot catch fire. So it can be baked at 180–200°C. A normal oven would burn it. No chemicals are used.

Vacuum kiln, no air · Sozen

180–200°C

No air, so the wood cannot burn. Baked evenly, right through.

Normal kiln · most makers

Hot air

Air inside, so the wood can catch fire at that heat. Baked from the outside in.

Baked wood soaks up less water. So it swells, shrinks and rots less.

Outside

Baked wood against normal wood (normal wood = 100)

Lower is better

Water it holdsAbout 50 at 220°C: half

Heat let through75–80: 20–25% less

Holds less water, so it swells, shrinks and rots less

International ThermoWood Association, ThermoWood handbook, April 2021

It comes in two colours: scorched black or deep brown.

Sozen tell us no other saunas in Indonesia are made this way. They are the only ones who bring this wood into Indonesia. They are the only ones here with the machine for it, too.

05 · The years after

Built to last

Canadian red cedar is rated to last 15 to 40 years. That is off the ground, as a sauna is.

Sungkai is rated to last 7 to 15 years. So cedar lasts 2 to 3 times as long.

Year after year, you open the door. The same smell is still there.

Durability

Rated life above ground

Longer is better

Red cedar15–40 years · class 2

Sungkai7–15 years · class 3

2–3× as long

Queensland Government, durability above ground; Forests, 2023

You touch the wood. You smell it. You breathe it. That is why we chose Sozen.

06 · Your sauna

Your sauna, and an ice bath beside it

Lots of people go from the sauna to the ice bath. Then back again. Heat, fresh air, then cold.

You can read what the research says about ice bath benefits.

Get a Sozen sauna with a Kaido ice bath. You save 10% on both.

See the Hot & Cold set. See the Phantom and the Oracle. Compare them in the price guide.

Phantom ice bath on a timber deck beside an infinity pool, the ocean beyond — A Kaido Phantom: the cold half of hot and cold.

Want to see one in place? Look at our installs. You can also book a call to talk it through.

Before you go in

Never alone. With a heart condition, high blood pressure or pregnancy, talk to a doctor first.

Start with short sessions. Drink water between rounds. Get out if you feel unwell.

Sauna wood Open the door, begin your red cedar experience