To build a sauna, plan a room about 7 feet high on a level, waterproof floor, frame and insulate it with a foil vapor barrier, line it with softwood such as cedar, add benches, and install a UL-listed heater sized for the room, wired by a licensed electrician. Plan a fresh-air inlet low near the heater and an outlet on the opposite wall, and hang the door to swing out. If you would rather skip the carpentry, a pre-cut sauna kit gets you the same result in about a weekend of assembly.
This guide walks through each step, the numbers that matter, and when building from scratch or buying a kit makes more sense.
Sauna building basics at a glance
| Item | Guideline |
|---|---|
| Ceiling height | About 7 feet |
| Size for 2 to 3 people | 4 x 6 ft to 5 x 7 ft |
| Width to lie down | 6 ft or more |
| Floor | Smooth, level, waterproof: tile, concrete or vinyl, never carpet |
| Insulation | Fiberglass plus an aluminum foil vapor barrier; the ceiling matters most |
| Heater | UL-listed, sized to the room; electric models range from about 1.5 to 15 kW |
| Ventilation | Inlet (about 4 x 6 inches) low on the heater wall, outlet on the opposite wall below the upper bench |
| Door | Swings out, ideally on a longer wall |
| Maximum temperature (US) | 195°F under the UL 875 safety standard |
Source for these guidelines: North American Sauna Society, "How to Build a Good Sauna". Always follow your heater's manual and local building code.
Step 1: Plan the location and size
First decide where the sauna goes. The North American Sauna Society names three deciding factors: the space you have, a shower nearby, and a place to cool off. Indoors, common spots are a basement gym, a master bath, a garage or a spare room. Outdoors, a sauna can stand on a patio, near a pool or anywhere in the yard.
Next, pick the size. Do not build it too small: 4 x 6 to 5 x 7 feet suits two or three people. A room close to a square, or about 6:4, heats more evenly. If you want to lie down on the upper bench, make the room at least 6 feet wide.
Building outdoors? Read where to put a sauna in the yard and check permits with your building department before you start.
Step 2: Prepare the floor or base
Indoors, the floor should be smooth, level and waterproof: tile, concrete or vinyl, never carpet. A floor drain makes cleaning easier and lets you use water more freely. Outdoors, the sauna needs a level base such as a gravel pad, pavers or a concrete slab. Our sauna site prep guide covers base options.
Step 3: Frame and insulate
Frame the walls and ceiling, then insulate them completely. The ceiling is the most important place to insulate well, because heat rises. The North American Sauna Society recommends regular fiberglass insulation with an aluminum foil vapor barrier. Install the foil carefully over the insulation, so moist air cannot reach the framing.
Step 4: Line the room with wood
Inside, use softwood boards. Cedar is the classic choice; spruce and hem-fir are also used. Sauna Supply Co. recommends installing the ceiling boards first and then the walls from the top down, so each board laps correctly. Do not use ordinary paint or varnish inside. If you want to treat the wood, use a product made for saunas, such as Meldos sauna oil ($174).
All our Canadian Timber saunas use Eastern White Cedar.
Step 5: Build the benches
Put the main upper bench along the longest wall. A higher bench sits in hotter air, so two levels let people choose. Use smooth, knot-free boards, round off the edges, and fasten them from below so no screw heads touch skin. Keep the heater guarded, so nobody can fall against it.
Step 6: Choose and install the heater
Use only a UL-listed heater, and size it to the room volume. Electric sauna heaters typically range from 1.5 to 15 kW, with breakers between 15 and 60 amps, according to the North American Sauna Society. Have a licensed electrician check your panel early and wire the heater. A wood-burning stove needs no power, but it needs a chimney and the maker's clearances.
Not sure what size you need? Read how to size a sauna heater. These are the heaters we sell:
- Harvia KIP: electric, wall-mounted, thermostat and timer built in, $1,211
- Homecraft Revive: electric, 200 lbs of stone, from $2,986
- Huum DROP: electric with WiFi app control, from $3,097
- TimberGlow 14: wood-burning, no electricity needed, from $2,339
For wood heat, see how to choose a wood-burning sauna stove.
Step 7: Add ventilation
Good ventilation is one of the most overlooked parts of a sauna. Fresh air makes the room more comfortable. The common layout is an air inlet of about 4 x 6 inches near the floor on the heater wall, often just below a wall-mounted heater, and an outlet on the opposite wall just below the upper bench. Follow your heater manual if it gives other instructions. For vent sizes, wood-stove setups and the two schools on intake placement, read our sauna ventilation guide.
Step 8: Hang the door and finish up
The door should swing out, ideally on a longer wall. A glass door or a small window brings in light and makes the room feel larger. Finally, add a thermometer, a bucket and ladle, and backrests. Our sauna accessories start with the Starter package at $98.
Is it cheaper to build or buy a sauna?
It depends on what you count. A DIY build can cost less in materials if you already have tools, skills and a good lumber source, but your time, mistakes and the heater still add up. A kit gives you a fixed price, pre-cut wood, instructions and a manufacturer warranty.
| Build from scratch | Pre-cut kit | |
|---|---|---|
| Wood and parts | You source and cut everything | Pre-milled cedar, hardware included |
| Plans | Your own | Assembly videos and PDFs |
| Time | Depends on your tools and skill | About a weekend for two people (barrel kits) |
| Price | Depends on lumber prices and your time | Known up front |
| Warranty | None | 5-year residential limited manufacturer warranty |
For a deeper look, read barrel sauna kit vs DIY build and how much an outdoor sauna costs.
Sauna kits we sell
Our Canadian Timber kits are pre-cut in Eastern White Cedar by Dundalk LeisureCraft in Ontario. Prices are for the sauna only; you choose the heater separately. Freight is free curbside in the lower 48.
- MiniPOD: pod, 4 people, $5,956.50
- Harmony, Serenity, Tranquility: barrel, 4 to 6 people, from $5,976.50
- Elation: barrel with a flat floor, 4 people, $6,975.50
- Granby, Palmer, Georgian: cabin, from $6,136.50
- Luna: rounded cabin, electric only, $7,391.50
- Avalon: cabin with three bench tiers, $11,344.50
Prefer no assembly at all? The Sweaty Yeti Sauna ($29,700) arrives as a finished sauna house with an electric heater and is set in place by the delivery crew.
How to build a sauna: FAQ
How high should a sauna ceiling be?
About 7 feet, according to the North American Sauna Society.
What wood is best for a sauna?
Softwoods such as cedar, spruce or hem-fir. Cedar is the classic choice. Skip ordinary paint and varnish inside.
Do I need a vapor barrier in a sauna?
Yes. The North American Sauna Society recommends fiberglass insulation with an aluminum foil vapor barrier.
Can I build a sauna without electricity?
Yes, with a wood-burning stove such as the TimberGlow 14. It needs a chimney and the maker's clearances instead of a circuit.
How big should a home sauna be?
For two or three people, 4 x 6 to 5 x 7 feet. Make it at least 6 feet wide if you want to lie down.
Do I need a permit to build a sauna?
Often, yes, for the structure and especially the electrical work. Ask your local building department before you start.
Ready to build?
Browse outdoor saunas and sauna heaters, or read the outdoor sauna buying guide. Questions about a kit or a heater for your own build? Call +1 (307) 309-8328.