The tension-easing relief a sauna offers can do wonders. It’s a tradition historically linked to Finland, where pits dug in the sides of slopes were heated with fireplaces, hot stones, and steam. Luckily, it’s possible to build one of these cozy relaxation rooms at home without digging a hole in the side of a hill.
Read on to learn the basics of building a home sauna plus factors to consider before you begin.
How To Build a Sauna: The Need-to-Knows
Before building this luxury typically reserved for spas and health clubs, there are a few things to think about.
Inside or Out?
The most important decision to make when planning to build a home sauna is whether it should be located indoors or outdoors. An indoor sauna can be built in a closet, basement, or bathroom if the proper precautions are taken. Since the structure, electricity, and ease of access are already in place, building an indoor sauna can be an attractive option.
An outdoor sauna requires a separate structure, either newly built or repurposed. An old shed might make a great spot for a sauna, but it will likely need to be wired for electricity (depending on the sauna type). Otherwise, a sauna can be built on a deck, on grade, on a concrete slab, or almost anywhere else that’s level and flat.
Kits vs. Custom Builds
There are sauna kits available that come with almost everything necessary to turn a shed or interior room into a sauna, and they’re worth considering. But an experienced DIYer can save some money by building a custom sauna without a kit. The chief consideration will be the builder’s experience level. If you’re a seasoned DIYer eager to personalize your home sauna (and save a few bucks), a custom sauna is worth the work. If you’re less experienced and/or have time constraints, for speed and simplicity, go with a kit.
There are three heater types to choose from electric, gas, and wood. Electric and gas are both efficient and heat quickly, and they will typically require an electrician or plumber’s expertise. Wood may be a better option for building an off-grid sauna, though wood-fueled saunas take longer to heat, and the temperature is harder to control.
Saunas produce high temperatures and moisture levels, so the materials used matter:
- Wall insulation should be fiberglass batt
- A foil-faced vapor barrier should be used over the insulation, and any seams should overlap by at least 4 inches
- Softwoods like cedar, poplar, and hemlock will swell and contract without cracking. Cedar is the most desirable, as it’s antimicrobial and smells and looks great, but it’s expensive. In a pinch, rough pine will also work, though it won’t last as long.
- Glass elements such as doors and light fixtures must be tempered to prevent cracking. And any electrical boxes or devices should be rated for high-humidity areas.
How To Build a Sauna: The Basic Steps
Building plans for home saunas will vary widely, but they’ll share basic characteristics that are important to note whether you’re DIYing it or enlisting a contractor’s help. The following steps explain the basics of how to build a custom electric- or gas-powered sauna of any size, with tips for indoor or outdoor builds.
1. Prepare the Location
Decide whether the sauna will be indoors or out and prepare the location. For indoor saunas, remove everything from the room, exposing the walls down to the studs. For outdoor saunas, find a flat, level spot large enough for the sauna.
Regardless of the sauna’s location, the floor should be waterproof. For outdoor saunas, this usually means starting with a concrete foundation. For indoor saunas, concrete board, waterproof floor membrane, and a skim coat of concrete or tile will typically do the job.
2. Install the Electrical
With the studs exposed, run wires for the electric heater if you’re using one, the thermostat, lights, and any other devices the sauna will include. Drill through the studs, run conduit, and pull the appropriate wires for the devices. If you’re using an electric heater, be sure there’s enough room on the breaker to handle its power draw.
3. Insulate the Walls and Ceiling
Install insulation between the stud bays and ceiling joists. Be sure to use the appropriately sized batt insulation for the stud and joist sizes (2x4, 2x6, 2x8, and 2x10 commonly) as well as the bay width (12, 16, or 24 inches, on center).
4. Install the Vapor Barrier
Install the foil-faced vapor barrier over the insulation, securing it to the studs and joists with staples. Install a lower course around the room before installing the upper course and then moving to the ceiling. Be sure that the upper course overhangs the lower course by at least four inches and create as few seams as possible. Where seams are unavoidable, seal them with foil tape.
5. Install the Paneling
Starting on the ceiling, install the paneling across the sauna space. For the first board, nail through the face of the board and into the joists, ensuring that the tongue is facing away from the wall. For each subsequent course, line the groove up with the previous board and nail through the tongue and into the joists. Repeat the process for each wall.
Note: Be sure to maintain a roughly ¼ -to ⅜-inch gap around the perimeter of the ceiling and each wall. This space will allow for the expansion and contraction that naturally occurs in a sauna. You can cover the gaps with small strips of paneling cut on a table saw.
6. Build the Bench
Measure the distance between two parallel walls. Build a simple frame with 2x4 stock and screws that spans the distance and measures 19 inches deep. Cut four 2x4s to 16 inches for legs. Situate the bench with a leg positioned vertically and flat against the wall in each corner. Screw the legs to the walls and then screw the frame to the wall. Finish the bench with 2x4 stock spaced ¼-inch apart.
7. Install the Heater and Light Fixtures
Install the heater in the sauna by either plugging in the electrical cord or plumbing the gas pipe (be sure to check gas piping for leaks). Install the light fixture(s), switches, and thermostat as well.
8. Test the Sauna
Set the thermostat to the desired temperature and close the door. Wait the suggested amount of time before checking the temperature in the space. Use the dipper spoon to pour a bit of water over the heater’s rocks, and enjoy the sauna’s relaxing, steamy atmosphere.
Tools and Materials
The tools required for building a home sauna will vary depending on the size and design. A general set of hand and power tools will be necessary, including:
- Power saws (circular, miter, and table)
- Power drill
- Tape measure
- Staple gun
- Finish nailer
- Pliers (linesman, pump, and slip joint)
- Safety glasses and hearing protection
Materials will also vary based on design, but in general:
- 2x4 or 2x6 framing lumber
- Cedar, poplar, hemlock, or pine tongue and groove paneling
- Nails, screws, and staples
- Waterproof membrane
- Floor tile and thinset
- Sauna heater and thermostat
- Electrical boxes, fixtures, and wiring
- Fiberglass batt insulation
- Foil-faced vapor barrier
- Foil tape
With your newly built home sauna, you’ll be able to enjoy a steam bath any time, even without a fancy spa membership. You can get as creative as you’d like with this basic design, so feel free to build the sauna of your dreams.