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.
Same benches. Smaller footprint.
The Medium Square keeps the Square's 78-inch rear bench, and a 35-inch side bench turns the corner, so you can sit facing each other instead of in a row. The covered porch has two outside seats for cooling down between rounds.
The shell is thermally modified Nordic spruce, 1.57 inches thick and made in Estonia. Thermory cites 25 years of proven rot resistance for this wood. That is a property of the wood, not the warranty. Keystone staves at the top and bottom point every stave upward, so the walls shed water.
We walked three Thermory plants in Estonia in September 2026 and watched boards scanned and graded on the line.
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 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.
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 sauna price does not include a heater. Your selections update the total 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
Every package fits this room.
We checked each heater against its manual: the room size once the glass is counted, the 79-inch ceiling, and the space it needs above, below and around it. 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.
▶ Watch the complete buildThe first Square sent to North America
We learned on its big brother.
Ben Frizzell still owns the first Thermory Square sent to North America, a No 40, and built it on camera near Bend, Oregon. It has been our test bench for heaters, ventilation and bench layouts ever since. The Medium goes together the same way: cradles, staves, the glass front, the rear panel, benches and roof.
Watch the build before your crate arrives. Thermory recommends two people for assembly; plan on about a day, plus electrical work.
The video shows an earlier, larger kit with some preassembled panels. Today's kits use individual staves, so follow the current manual for the order of steps.
A 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 98.9. 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?
All four packages fit the Medium Square. 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.
Prebuilt
Sauna Brushes
Vents