When building an outdoor sauna, you need to first decide where you would like to keep your sauna and how large your sauna should be. For this part of the project, you will need wood, insulation material and adhesive.
Most saunas are made from cedar, because of its ability to stay cool and to absorb steam. It is also resistant to weather and the steam inside the sauna and has a pleasing aroma.
When purchasing your wood, keep in mind the size of the building you want and how tall your sauna will be. Most 2x4 planks of wood are approximately 8 feet long, though other sizes are available. Make sure you purchase the wood for the walls and doors as well as studs for the walls. For the frames of your walls, consider using oak or birch.
Before constructing the walls and door, you must have previously built the floor. If you have not completed the floor, you can do so by nailing 4 pieces of 2x4 oak or birch lumber on the ground to build a frame. After that, nail plank boards over the 2x4s to finish your floor.
When you begin building you walls, make a frame with the oak or birch. Build the outer walls, and then stand them up and attach them to the floor, making sure that there are no cracks anywhere except for the space for the door and the roof.
Place insulation between the boards that make up the frame and supports, making sure the material covers every inch of the area that touches the outside walls. This will prevent the steam or heat from escaping your sauna, keeping it warm inside.
After the insulation is complete, attach the cedar planks to the frame inside the sauna by nailing them to the studs and over the insulation. If you are planning to attach benches to the walls, make sure to mark on the wood where the studs will be behind the walls.
Measure the area of space that you want for your door. Your door must perfectly fill the space so that it lets very little air out of your sauna, but at the same time, it should easily open and close.
You can make a simple sauna door out of a frame and pine. If you would like extra insulation on your door, make sure that you build the door thick enough to hold the insulation.
After the door is constructed, attach hinges and hang the door. Add a handle and a latch to keep the door closed.