To build a sauna in a basement, begin by first deciding on the size, type and location of the unit, then build a frame, install power lines, install the walls and interior planking, and install the heater. Saunas may be wet or dry and may be heated by electricity, wood, gas or infrared lamps. A gas sauna requires ventilation and a carbon monoxide detector, a wood sauna needs a chimney, and infrared heating cannot be used for a wet sauna.
A sauna may be any size, but a smaller space is easier to heat evenly. A typical compact sauna measures 5 by 6 feet with a 7-foot ceiling.
Locating a sauna in the corner of a basement means building two less walls. When framing, leave a 4-inch space between the existing concrete or cinder block wall and the interior wall of the sauna, and between the floor of the basement and floor of the sauna. Install insulation between the framing studs to help retain heat. Run power lines to the unit before building the walls.
Attach 1/2-inch plywood to the frame for the walls, ceiling and floor, and then attach red cedar planks to all interior surfaces. Build the door from plywood covered in cedar. The door must swing out for safety reasons.
Install the heating unit. Add benches to the interior for seating.