Sauna walls
For this construction you need wood, adhesive. Choose the place where you want the sauna to be and how large you want to make it.
Wood sauna
Because of the need, the wood must stay cool and absorb the steam and it has to resist to the water.
Exterior walls
You have to build first the floor if you haven’t yet. Nail 4 pieces of 2×4 oak/birch lumber on the ground to make the frame. To finish, you just need to nail planks on the 2x4s.
Make a frame for the walls from oak or birch. Attach the walls to the floor after you stand them up. Be sure that the only spaces are those for the door and roof.
Insulation
Between the boards put the insulation material. Be careful you don’t leave any empty spaces. Thanks to this material the sauna will maintain warm because the heat and steam will not go out.
Interior
Over the insulation, to the frame, nail the cedar planks to the studs. The studs will be behind the walls, so if you want to install benches, mark the place of the studs.
Door
The door must open and close easy and also it must be fit perfectly that the air will not go out so measure carefully. From a frame and pine you will make a simple door. The door must be thick if you want to put on it insulation just like on the walls. Put some hinges and hang the door and to maintain the door closed put a latch and a handle.