Build Your Own Sauna

These considerations will guide you in constructing a room where you can turn up the heat to flow off some steam.

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by Pixabay/TheUjulala

In Minnesota, where I live, the use of saunas is quite common, and it’s not unusual for people to have a sauna in their backyard or basement. Health clubs, fitness centers, and even hotels may list saunas in their marketing materials, touting their health and fitness benefits. The widespread use of saunas in Minnesota and the Upper Midwest can probably be traced back to the many Finnish immigrants who came to the area in the late 1800s to work in the lumber and mining industries. Taking a “sauna bath” was a tradition Finnish and Scandinavian settlers brought with them from their homelands, with the sauna’s origin going back about 2,000 years. At one time, the city of Duluth, Minnesota, had 12 public saunas available for a fee, and the Duluth Family Sauna – which is still in operation – has been available to the public since 1921.

Though I had used saunas in health clubs, my first true sauna experience was in a friend’s outdoor free-standing sauna on the shore of a Minnesota lake in December. After staying in the sauna for half an hour, we bolted across snow-covered ground and ran into the lake, which was not yet frozen for winter. The sensation – both exhilarating and frightening at the same time – is one that will stay with me for a lifetime. While you may not have a lake available to plunge into after a hot sauna, you can still experience the soothing, relaxing, and cleansing benefits of a sauna that you’ve built yourself.

outdoor sauna in a backyard during winter

Sauna Heaters

According to the North American Sauna Society, the definition of sauna is “a specific room heated to about 150 to 195 (F) degrees, and where the temperature and humidity of the room can be controlled with sprinkling water on the rocks in the heater/stove.” The traditional Finnish sauna is a dry sauna with relative humidity in the 10 to 60 percent range, compared with a Turkish-style steam bath, which has 100 percent humidity. While all saunas share a similar construction form, the different types of saunas are defined by their heat source.

A woodburning stove is the most traditional type of heat used in a sauna. The fire in the stove heats rocks placed on top of the stove – usually igneous rocks, which are formed when molten rock solidifies – to attain a temperature between 140 and 200 degrees Fahrenheit. Then, water can be poured on the rocks to create steam. Woodburning saunas are normally found in a free-standing structure that’s not connected to a home, because of the fire risk. Woodstoves are also the only option for heating your sauna if you’re building in a remote area without access to electricity. While woodstoves are the most traditional type of sauna heater, they do require additional work to prepare the fire before a sauna, and they also require the cleaning out of ash buildup after use.

Electric sauna stoves produce a similar experience to that of woodstove-fired saunas, but don’t require the starting or feeding of a fire. Most electric sauna stoves require 220-volt wiring and are hard-wired to the electrical box. Electric saunas are a good fit for urban areas and can be installed indoors, so you could convert some unused basement space or a storage room into a home sauna. They’re also an excellent choice for outdoor free-standing saunas, but they do require extra planning for connecting electrical wiring.

outdoor sauna covered in snow

Infrared heaters are another option for saunas. The radiant heat produced by an infrared heater differs from traditional sauna heaters in that the infrared light heats the body from within as opposed to heating the air.

When pricing sauna stoves, the biggest factor in determining cost is the size of the sauna. Stoves need to heat the sauna to temperatures between 150 and 195 degrees, so the larger your sauna’s size and capacity, the more output you’ll need from your stove. Smaller saunas in the 4-by-6-foot range don’t require as large of a heat source compared with a 6-by-8-foot sauna or a 12-by-12-foot sauna, and prices will vary based on stove output. Expect to pay anywhere from $800 to more than $3,000 for a sauna stove, depending on the size of your sauna and the type of heater you choose.

Indoor Versus Outdoor Sauna

Deciding where to build your sauna will have a lot to do with where you live, how much space you have, and the number of people you anticipate will use the sauna at one time. Because personal saunas typically aren’t large, you can build a 2-to-4-person sauna in a basement, spare bedroom, or storage room, or even in a corner of your garage. You don’t have to be concerned about excessive moisture created by an indoor sauna, as the humidity levels rarely exceed 30 percent; a bathroom shower can generate two or three times more humidity than a sauna. The floor of the sauna can be concrete, vinyl, or tile, but never place a sauna over a carpeted floor.

interior of a wood sauna steaming

Outdoor free-standing saunas can be built in any space able to fit a garden-style shed. The main consideration with free-standing saunas is that you’ll need to have a solid, level foundation for the sauna, usually constructed of cement. The outdoor structure doesn’t have to be too large, as a typical sauna has a 7-foot-tall ceiling, with common sizes for a two- or three-person sauna at 4 by 6 feet or 5 by 7 feet. Of course, you can build a sauna up to 12 by 12 feet or larger, but you’ll also require a greater heat output, which will translate into a more expensive stove to heat the increased area.

Whether you choose to build a sauna indoors or outdoors, consider its access to a changing room and a shower. Having either a glass door or a window in the sauna will create a much less claustrophobic environment. Also, if you choose to use a lot of water on your sauna stove – creating a more humid sauna – you may want to include a drain in the sauna floor.
DIY Sauna

If you’ve decided to invest in a sauna and have basic carpentry skills, building your own can be a rewarding project. The first step is deciding where to build. Adding a free-standing sauna inside your basement or garage will require less intensive work than tearing out an existing wall and part of a ceiling to create a built-in sauna room. If you’re in the process of remodeling a bathroom or basement in your home, that’s a great time to consider adding a sauna. Regardless of location, the basic construction elements are the same for all saunas.

If you’re building a free-standing sauna, once you’ve decided on the size, you’ll need to frame in the sauna. If you’re using an existing exposed wall and ceiling in a room, you’ll need to frame out the sides and front of the sauna. The door for the sauna should also be roughed in when framing; most sauna doors are narrow to conserve heat. A standard door is 24 by 80 inches, with a rough opening of 26 by 82 inches, but sizes may vary by manufacturer if you decide to purchase a finished pre-hung door. When considering sauna size, a good rule of thumb is 2 feet of bench space per person, so a 4-by-6-foot sauna will hold 2 to 4 people. You’ll also need at least 6 feet of bench length to recline in the sauna, and the optimum height for a sauna is 7 feet.

interior of a sauna with piled up rocks in the center and a step up

Sauna Wiring

After framing out the sauna, the next step is to add wiring. If you’re not highly qualified, the wiring for a sauna is best left to an experienced electrician. The voltage for electric sauna stoves is 220 volts, which may require adding additional electric service to your existing circuit box and will also require the correct gauge of electrical wire for the project. The high-voltage requirement of electric sauna stoves may create a fire hazard or even cause electrocution if done improperly. Whether you choose a wood or electric sauna stove, you’ll also have to run wiring for any indoor lighting and for the electric stove controller if your model requires it. You’ll also need to wire a temperature sensor inside the sauna that attaches to the stove and any associated remote controller.

Sauna Insulation and Vapor Barrier

Even if you locate your sauna indoors, you’ll need to insulate the walls with a good roll insulation of at least an R-11 value. This will help build and retain heat inside the sauna in a shorter amount of time, which will save on the electrical costs and help the stove run more efficiently. Roll insulation comes in either 16- or 24-inch width, depending on the distance between your wall studs. Insulation also acts as a sound barrier, which will help provide a more tranquil environment inside the sauna.

A foil barrier designed for saunas installed over the wall insulation is absolutely critical for keeping moisture in the sauna from escaping into the insulation and the walls outside the sauna. Staple the foil to the walls and ceiling of the sauna with a 3-inch overlap. The small amount of steam created by putting water on the rocks in the heater will be absorbed by the wood in the sauna or exit via a small vent. The heaters in the sauna are sometimes allowed to stay on a little longer after the sauna has been used to help dry out the interior wood.

Interior Finishing

The interior of the sauna is constructed of 3/4-inch tongue-and-groove paneling that’s usually 4 inches wide and 7 to 8 feet long. The type of wood used in saunas has typically been clear cedar because of its pleasing aroma and its ability to absorb moisture without shrinking. However, softwoods, such as hemlock and white spruce, are also usable and can be much more economical. The higher cost of lumber due to the closing of Canadian borders and lumber mills during the pandemic has also affected the overall cost of materials for a sauna, as much of the cedar and other lumber is sourced from Canada. Prices might drop if production increases in the coming months.

When finishing the interior of the sauna, start with the ceiling. Nail the tongue-and-groove paneling perpendicular to the studs by nailing through the tongue at a 45-degree angle. The nails used for the interior of the sauna should be stainless steel, 2 inches long, and in 18-gauge size. Using a pneumatic brad nail gun will make the installation much easier than attempting to hand-nail the wood.

an outdoor sauna next to a small pond

The next step is to install the tongue-and-groove paneling horizontally over the walls of the sauna. Start at the bottom of the sauna, with the groove down and tongue up. Keep adding boards, checking for level every three or four boards. In the ceiling and the walls, you’ll need to plan for and cut locations for lights, switches, vents, and other electrical connections.

Benches, Stove Mounting, and Door Hanging

Inside a sauna, there’s an upper and a lower bench. The upper bench should be 18 to 24 inches deep and 36 inches high. The lower bench is normally situated 18 inches off the floor. The upper bench is the hottest zone in a sauna, while the lower bench is used for cooling off and as a step to reach the upper bench. Wall cleats constructed of the bench material are used to hold the sides of the bench, and the back of the bench is screwed securely into the framing studs. For longer bench lengths, you can add leg supports.

Mount the sauna stove based on its manufacturer’s specifications. Sauna stoves usually come with explicit instructions and even a template with instructions on where and how to mount the stove based on the layout of your sauna. With electric stoves, most manufacturers recommend placing a vent for proper air circulation somewhere near the floor by the heater and an upper vent about 6 inches below the ceiling on the wall opposite the heater. You’ll also need to construct a sauna heater guardrail to prevent users from accidentally bumping into the heater. Wood-fired sauna stoves require the additional preparation of outside chimney venting.

You may choose to build your own door and frame, but I’d recommend purchasing a pre-hung sauna door from one of the many manufacturers of saunas. Using a pre-built door will give you many different options for either a full or partial glass door to provide natural light to the sauna. You may also want to frame in a window for additional natural light. Custom framed windows can also be purchased individually from sauna dealers and manufacturers.

Sauna Accessories and Kits

There are many sauna accessories that are useful and add flair to the sauna experience. You can purchase custom door handles, water buckets and ladles, and even head and foot rests online.
If you want to build the majority of the sauna yourself but don’t want to build the benches and supports, you can also order those from manufacturers. If you only want to frame out and wire the sauna space, you can order sauna kits from manufacturers that come ready to be assembled on your framing and take less than a day or two to completely assemble. Depending on your skill level and price range, you can choose from many styles of sauna kits to venture full steam ahead into building your own backyard sauna.

Tim Nephew is a frequent Grit contributor and equipment specialist. He lives in rural Minnesota, where he owns and maintains 80 acres of wildlife habitat.

  • Updated on May 24, 2022
  • Originally Published on Dec 10, 2021
Tagged with: electric heat, infrared heater, sauna, woodstove
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