Structures designed for people to sit in high temperatures have been popular throughout the world for thousands of years. Experts may debate the specific benefits, but many people experience an increased feeling of well-being from taking a sauna. (Of course, you should always consult your doctor first.) Having a sauna in your own home may seem like an unattainable luxury, but it can be a surprisingly DIY-friendly project.
One of the biggest misconceptions about in-home saunas is that they create the same potential humidity-related problems as steam baths. But saunas and steam baths are not the same. A steam bath or steam shower generates high temperatures (up to 110 degrees) and high humidity levels (often near 100 percent), so installing a steam room requires many construction precautions to contain the moisture and prevent damage. Saunas create even higher temperatures (140 to nearly 200 degrees) but low humidity (typically less than 15 percent). Even when water is poured on hot rocks in a traditional sauna, the humidity level rises to only about 30 percent for a few moments and quickly drops back down. Because saunas are very dry, they do not cause moisture damage.
Another misconception is that home saunas are too expensive and too complicated for homeowners to build, but that’s simply not the case. You don’t even need a lot of extra space — in fact, smaller saunas are more efficient, requiring less powerful heaters and heating up more quickly. The most common size of traditional sauna installed in a home is roughly 5 x 7 ft., which will seat two to four people. If your space is really limited, you can still install a one-person, freestanding infrared sauna in a 3 x 3-ft. space.
We asked a Finnleo expert a few questions about saunas; check out the video below.
There are several approaches to building a sauna in your home. The fastest and easiest DIY option is to purchase a prefabricated kit that includes factory-built walls and ceiling panels. All you have to do is connect the panels (or easier yet, hire the sauna dealer to assemble them for you). These kits can be assembled and fully functional in just a few hours.
The other end of the construction spectrum is to build the sauna from scratch. This will require a lot more time and research, but it allows you the freedom for complete customization, and it can also be much more economical if you’re thrifty when buying materials.
The happy medium between prefabricated and built-from-scratch is to purchase a precut kit from a sauna manufacturer. I recently installed a precut kit manufactured by Finnleo Sauna, based in Cokato, Minnesota. I submitted detailed measurements of the space, and the company provided a construction drawing for my approval. Once the drawing is approved, it typically takes a few weeks for the company to cut and ship the tongue-and-groove siding, benches, door and windows. The heater and control panel are also included with the kit. I was responsible for the framing materials and insulation.
Installing a precut kit is a project that can be completed by an experienced DIYer in a weekend. The only power tools necessary are a miter saw, a jigsaw, a drill/driver, an 18-gauge brad nailer and a compressor. (You could hand nail the siding boards, but that would take a lot longer.)
Ideally, a sauna should be installed near a shower so that you can rinse off immediately afterward. If you’re not lucky enough to have 35 sq. ft. of extra space in one of your bathrooms (and few people are), the next best option is often in an unfinished corner of the basement, or in a warm climate, you might consider the back of your garage. Even the empty space under a stairway is often sufficient for a one- or two-person sauna.
Most traditional saunas require a 240-volt circuit to power the heater as well as a 120-volt circuit for any lights or other electronic accessories. Check the manual of the heater you select for specific power-supply requirements. All electrical work should be done and inspected by approved professionals.
Traditional vs. Infrared
One of the first decisions you must make when planning a sauna installation is what type of heat you want: traditional or infrared. Traditional heaters use heating coils that are covered with special rocks. The heater radiates warm air, which in turn warms you. Traditional saunas allow you to add steam to the environment by tossing water on the hot rocks.
Infrared (also referred to as far infrared) saunas are easily recognized by the dark horizontal panels that clad their interior. These saunas use infrared light rays to heat your body without warming the air. Some people prefer the hot environment of a traditional sauna; other people prefer the lower room temperature of an infrared unit. The only way to know what’s best for you is to visit a sauna dealer and experience both types of heat for yourself. If your family can’t agree on which type of heat is best, you don’t have to install two saunas; the Finnleo Infra Sauna features both types of heat in one unit, so everybody wins.
Materials and construction
A sauna is simply an insulated box with a door. Frame the walls and ceiling with 2x4 lumber, following standard 16-in.-OC framing practices. It is important to frame openings for a 4 x 6-in. air inlet (see photo 1, below) and a similar-size air outlet to provide fresh-air exchange. The inlet is typically located at the base of the wall directly under the heater, and the outlet should be installed approximately 24 in. above the floor in the wall opposite the inlet, often just under the upper bench.
Wood is the only material recommended for the interior siding, but it is acceptable and increasingly popular to use other materials, such as stone or glass block, in small areas as accents. Softwood species are the ideal material for the interior surfaces because they do not absorb heat and get as hot to the touch as hardwood. Avoid stock with large knots, which do get very hot to the touch, or stock with visible sap, which will run when it is heated. Cedar, hemlock and poplar are popular options in North America; Nordic white spruce remains the preferred choice in Scandinavia.
You can clad the exterior with whatever material you like. The most popular choice is to use the same or similar wood siding that was used for the interior to maintain a traditional sauna appearance. Another option is to use a material (typically drywall) that blends in with the surrounding walls.
How to install your own sauna
Our Custom Cut sauna kit arrived in boxes that were clearly labeled with the contents and roughly organized in order of installation. The kit included complete instructions and all necessary materials, with the exception of the framing lumber and insulation.
Frame the walls and ceiling using standard 16-in.-OC framing practices. You must frame 4 x 6-in. inlet and outlet air vents. Frame the inlet vent directly below the heat location at floor level (pictured). Frame the outlet in the opposite wall with the top of the vent 23 in. above the floor. After the wall siding is installed, the inlet vent opening is finished with a fixed-louvered grill (inset photo) and the outlet vent is finished with a sliding-door valve.
Insulate the walls and ceilings. We used R-13 unfaced insulation in the walls and R-19 in the ceiling. You can also use faced batts, but you must install the facing on the interior side of the framing.
Attach the foil vapor barrier to the framing using a staple gun, overlapping the seams by a couple of inches. Besides serving as a vapor barrier, the foil reflects radiant heat back into the sauna.
Install the interior siding, starting with the ceiling, then the back wall, then both side walls (pictured) and finally the front wall. Start each wall with the groove edge of the board against the adjacent wall. Use an 18-gauge brad nailer to face nail at each end of the board (these will later be covered by corner trim) and drive nails through the tongue at each stud. Hold the gun at an angle and drive the nails into the back edge of the tongue so that they will be concealed by the overlapping groove of the next board.
Install the bench supports. Drive 3-in. screws through the bench supports and into the studs. The lower bench support runs to the back wall under the upper bench, allowing you to slide the lower bench back to create more open space for easier cleaning or access to the heater. In this case, the upper bench support features a front vertical framing piece to attach an apron.
One of the upgrades we chose for this project was to install a backrest with a built-in LED light strip. The strip is connected to a power supply that will plug into an outlet located in the room behind the back wall of the sauna.
Position the prehung door frame so that the front edge will be flush with the exterior siding or wall-covering material. Drive 3-in. screws through the hinge side of the door frame. Use shims to plumb and level the door, and secure the rest of the frame with 3-in. screws.
Mount the heater to the wall. We used the manufacturer-supplied template to mark the locations of the lag screws that will support the mounting brackets (inset). Loosely surround and cover the heater coils with the rocks provided by the manufacturer.
Connect the control pad to the temperature sensor and heater. This control pad features a touch screen and is connected to the heater with a CAT5 cable.
Countless upgrade options are available, including audio systems (top photo) and even televisions, but most people prefer to keep the sauna simple. A quiet, dimly lit environment is typically best for relaxation. The Saunatonttu heater (bottom photo) is the latest advancement in traditional heaters. A super-insulated shell uses a small standby heater to keep 200 pounds of rocks hot and ready for a sauna with no preheating time required.
The 3 x 3-ft. footprint of this infrared unit (left photo) will fit in just about any room. Traditional saunas feature wood walls, but you can customize yours by incorporating other materials, such as stone (right photo), as accents.
The Essential Sauna
By Gary Legwold
It’s a cold, blustery, raw, gray, pile-on-the-layers day that has designs on dragging me into depression. But my defense is my 4 x 6-ft. basement sauna, which I just turned on.
As this electric sauna warms into the thermometer’s red zone between 180 and 210 degrees F, I want the day to get worse. Bring it on — give me your best shot with all the foul weather you can muster! I won’t cower; I’ll stand naked and thumb my nose at it, knowing that I’m steps away from being cozy in my dark, double-bench cocoon, sweating away all gloom and singing life’s praises.
The sauna tour:
When I assembled my sauna from a kit years ago, I at first considered this a luxury project inspired by a three-city (Turku, Tampere and Helsinki, Finland) sauna tour I took. Tough assignment, but I gutted out the daily grind of testing saunas and eating well.
The tour ended at the 4,200-member Finnish Sauna Society in Helsinki. The facility includes five saunas heated with firewood and three savusaunas, “smoke saunas” with chimneys to let smoke escape. Typically, you start in a mild sauna, progress to hot and then finish with a savusauna, which has an intense but very smooth heat.
After each sauna, you go to a porch leading to a hole in the ice covering the Helsinki Bay. You can jump in, walk a slow death downstairs into the water or pass and enjoy the experience of being naked outside in winter and yet feeling absolutely comfortable and at peace.
Following the saunas, you shower and go to a cafeteria, where you are served beer, coffee or tea with sausages and mustard. Your day is pretty much done after that.
A sauna is not a luxury, in my book. It’s essential for mental, physical and even spiritual health. We are DIYers because we do projects to make our living spaces better — our kitchens, bathrooms, garages, etc. A sauna project will make living better. On bad days and good, a sauna will slow you down and pick you up.