Thermally modified wood
A solid Nordic spruce shell brings the warmth and texture of real wood, with improved stability and decay resistance for outdoor use.
The social layout. A shallower footprint.
Keep the long rear bench and the two-seat porch in a smaller space. The Medium’s L-shaped upper seating lets you sit at an angle to each other, with lower footrests and a glass front opening the room toward your backyard.
Room to share the ritual
Warm up together, step outside to cool down, and come back for another round. The porch seats make those pauses part of the sauna, too.
The rear bench is 6 ft 6 in long; the 2 ft 11.4 in side bench adds a place to sit. Choose the Large for more side-bench space.
Thermory quality, board by board.
At Thermory’s plants in Estonia, every board is scanned and graded on the line, so only the best wood ends up in your sauna.
Thermal modification is a controlled process: heat and steam, with schedules matched to the wood species and sensors monitoring the kiln. It improves dimensional stability and decay resistance without chemical preservatives.
That is why the Thermory name matters to us. The material, the milling and the quality checks all contribute to how the kit goes together and how the wood handles repeated heat, moisture and outdoor weather.
Explore Thermory at Sauna Marketplace
Made for the backyard. Built with care.
The rain jacket is included
The fitted roof cover protects the top of the sauna in wet weather. Install its securing slats as the manual shows and keep the cover in good condition.
The details still matter
A level base, correctly fitted glass, ventilation, band tension and drying after use all matter. We help you plan the build and care for the sauna afterward.
One layout. Two views.
Choose your rear wall.
Both models have the glass front, porch and L-shaped benches. The difference is the upper rear panel.
No 42: panoramic rear window
Choose it when the view behind the sauna deserves a seat, too. The rear window is 6.3 by 3.2 feet, so with the glass front you can see straight through.
No 43: solid wood rear wall
Choose it when the sauna backs onto a fence, a neighbor or a view you would rather leave outside. You keep the glass front and the same seating, and a solid back wall holds heat better.
See the choices before you choose.
These are views from our interactive 3D model. Use the product options above to select your sauna and heater; the viewer follows your choices.
3D previews show layout and equipment. The selected sauna and heater manuals govern installation, ventilation and clearances.
Check the benches, not just the headcount.
Thermory lists seating for four. The rear upper bench is 6½ feet long, which is room for one person to lie down. Look at the layout in 3D with the people you will use it with.
| Footprint, including porch | 82.7″ wide × 83.2″ long |
|---|---|
| Base (four cradles) | 78.7″ × 81.5″ |
| Height, including cradles | About 87.9″ |
| Interior height, floor to ceiling | About 79.3″ |
| Upper bench to ceiling | About 38.2″ |
| Heated room depth | 55.4″, plus a 19.3″ covered porch |
| Interior width | 75.2″ |
| Rear upper bench | 78″ long × 19.3″ deep |
| Side upper bench | 35.4″ long × 19.3″ deep |
| Volume | 191 cubic feet (Thermory) |
| Shell | 1.57″ thermally modified Nordic spruce; made in Estonia |
Measurements are from Thermory's current No 42 / No 43 drawing, which rounds its figures.
Use the drawing in the manual below to lay out the base. Leave room for the door swing, assembly and maintenance.
Know what you are buying
The sauna is the start of the package.
Included with the sauna
- Thermally modified spruce shell staves, four base cradles and two metal bands
- Glass front panels and a hinged door with handle
- The upper rear panel: panoramic window on No 42, solid wood on No 43
- Upper benches, bench steps, two backrests and the sauna floor
- Two porch benches and the porch floor
- Roof boards, the waterproof roof cover Thermory calls a rain jacket, a ventilation grill, hardware and the assembly manual
Choose with your order
- A Harvia KIP 8 kW, HUUM DROP 7.5 kW, Harvia Spirit 9 kW or Harvia Virta 9 kW package
- The controls, stones and accessories listed in that package
The first price is the sauna alone, before the heater package and shipping. Build the package that suits you; the total updates in the buying section.
Plan at your site
- A level base on concrete, pavers or crushed stone, raised so the cradles stay off the ground and clear of standing water
- Freight access and a plan to unload one crate
- Two people for assembly and room to work
- A 240-volt supply, wired by your electrician to the heater's instructions
Choose the heater around the way you use the room.
Heater selection has to account for the glass, ceiling height and required clearances as well as the room’s floor area. The glass front, and the rear window on No 42, add to the heat load, so the packages are sized for that. We favor a floor-standing heater in the Square family. We tried a wall-mounted heater in our own Square, and the curved wall forced it higher than we wanted.
The first Square in North America became our test bench.
Thermory’s assembly animation 16 minutesExperience from the first one
Ben Frizzell owns the first Thermory Square sent to North America. He built his No. 40 near Bend, Oregon. We have used that sauna to learn about heater placement, ventilation and bench layouts: the details that change the experience once you sit down.
Ask us where your feet will rest, how the heater occupies the room, or what to prepare before delivery.
This is our older Large No. 40, with some preassembled panels. Current kits use individual staves. The Medium and Small have their own dimensions and assembly instructions; follow the manual for the kit you order.
Talk through your Square with a BenA few things to get right before build day.
Start level.
The base sets up the door, glass and benches. Check that the diagonals match before you build upward, and tighten the metal bands again a few days after assembly.
Plan the unload.
It ships in one crate of about 1,800 pounds. Our Medium Squares have arrived by liftgate, but confirm with the carrier who unloads it and how before delivery day. Your heater equipment may arrive separately.
Give the wood some care.
The manual has you put two coats of varnish on the panel sides before building. Outside, the wood weathers toward silver unless you use a UV finish. Keep the roof cover in good shape and let the sauna dry after use.
Questions to answer before you order.
What’s the difference between No 42 and No 43?
The upper rear panel. No 42 has a 6.3-by-3.2-foot panoramic window; No 43 has solid wood. Both have the same glass front, porch, size and L-shaped benches.
How is the Medium different from the larger Square #40 and #41?
The Medium is about 16 inches shorter, 83.2 inches against 98.8. It keeps the same 78-inch rear bench and 19.3-inch porch. The side bench is 35.4 inches instead of about 51, and the room is 191 cubic feet instead of 241. Thermory lists the Medium for four and the larger Square for six.
How many people fit, and can someone lie down?
Thermory lists seating for four. The rear upper bench is 78 inches long, so one person can stretch out while others sit on the side bench.
How tall is it inside?
About 79.3 inches from the floor to the ceiling, and about 38.2 inches from the upper bench to the ceiling, on Thermory's current drawing.
Does it come with a heater?
No. The price is for the sauna kit. Heater packages in the selector add the heater, controls, stones and the accessories named in each option. Foundation, assembly, electrical work and freight are separate project costs.
Which heater should I choose?
The Harvia KIP 8 kW with built-in controls is the simplest install. The KIP with Fenix adds Wi-Fi control. The HUUM DROP 7.5 kW is the largest DROP that fits under the 79-inch ceiling with HUUM's required clearances. The Harvia Spirit 9 kW and Virta 9 kW give the most output, and both come with Fenix Wi-Fi control.
How hot can it get?
Thermory's manual sets 194°F as the maximum room temperature for this sauna.
What do I build the foundation on?
Concrete is best; a well-built deck, pavers or crushed stone also work. Keep it level, free of standing water, and raise the sauna so the cradles do not touch the ground. The base is 78.7 by 81.5 inches on four cradles; the manual shows their positions.
Can I assemble it myself? What does the electrician do?
Thermory recommends two people, and plan on about a day. Watch our build video, then follow the current manual. Your electrician installs the 240-volt supply, controls and sensor to the heater's instructions.
How does it ship and get unloaded?
By freight from a U.S. warehouse in one crate of about 1,800 pounds. Confirm the unloading plan with the carrier before delivery, and tell us about driveway access before the order ships.
What does the warranty cover?
Thermory gives the first owner a two-year limited warranty from delivery. It covers construction, manufacturing and material defects, and exterior rot or decay that makes the sauna unusable. Heaters, lights, electrical parts, glass windows and doors are excluded; the heater has its own warranty. Placing the sauna directly on gravel, grass or mud voids the coverage.
Why buy the Medium Square from Sauna Marketplace?
Ben Frizzell still owns the first Square sent to North America and has used it to test heaters, ventilation and bench layouts. You get that experience when choosing your heater and planning the build. We help with assembly questions and work with Thermory when a part needs attention.
What care will the wood need?
Varnish the panel sides before building, let the sauna dry after use, and keep the roof cover in good condition. The outside weathers toward silver unless you use a UV finish.
The instructions, right here.
Compare Thermory Squares
Which Square is yours?
Start with how you want to sit, then choose your rear wall. No. 40 and 41 share the Large layout; No. 42 and 43 share the Medium layout. No. 45 is the compact sitting sauna.
Compare all five models below. Every Square has a glass front and includes the rain jacket.
Matches your choices
No. 40 Large Square
Sauna kit $9,477.00
Panoramic rear glass
More side-bench room for time together.
- Outside · W × D × H
- 82.7 × 98.8 × 87.9 in
- Upper seating
- 78 in rear · 51.2 in side
- Cool-down space
- Two porch seats
- Rear wall
- See the view through both ends.
Matches your choices
No. 41 Large Square
Sauna kit $8,811.00
Solid wood rear wall
More side-bench room for time together.
- Outside · W × D × H
- 82.7 × 98.8 × 87.9 in
- Upper seating
- 78 in rear · 51.2 in side
- Cool-down space
- Two porch seats
- Rear wall
- Glass front, solid wood behind you.
Matches your choices
No. 42 Medium Square
Sauna kit $8,619.00
Panoramic rear glass
The same reclining length with 15.6 in less overall depth.
- Outside · W × D × H
- 82.7 × 83.2 × 87.9 in
- Upper seating
- 78 in rear · 35.4 in side
- Cool-down space
- Two porch seats
- Rear wall
- See the view through both ends.
Matches your choices
No. 43 Medium Square
Sauna kit $8,008.00
Solid wood rear wall
The same reclining length with 15.6 in less overall depth.
- Outside · W × D × H
- 82.7 × 83.2 × 87.9 in
- Upper seating
- 78 in rear · 35.4 in side
- Cool-down space
- Two porch seats
- Rear wall
- Glass front, solid wood behind you.
Matches your choices
No. 45 Small Square
Sauna kit $5,478.00
Solid wood rear wall
A compact sitting sauna for one or two.
- Outside · W × D × H
- 52.76 × 57.09 × 87 in
- Upper seating
- Compact sitting layout
- Cool-down space
- No porch
- Rear wall
- Glass front, solid wood behind you.
Dimensions include the porch where fitted; allow additional room for door swing, assembly, service and required clearances. The 78 in rear bench in the Medium and Large gives one person room to recline; the side bench is additional seating. Prices are for the sauna kit, before the heater package and shipping; you build the package that suits you. Review the package, delivery and tax on its product page.
Prebuilt
Brushes, Whisks and Body Care
Vents