Constructing a steam room is a little different than constructing a regular room. Moisture can be a major problem when normal building materials are exposed to it over time, so a real steam room must be properly waterproofed from the start. The process of constructing a steam room begins with selecting the right waterproof materials to build with, and after initial construction, you will need to take further steps to seal the room with more waterproof material.
Use a stud finder to locate the studs in your existing walls. Use a permanent marker to mark where the studs are. Once you have located the studs, use a hammer to tear down any standard drywall that was used to construct your walls.
Install a thick plastic sheath over the exposed studs and insulation as a water barrier. This will be important for preventing moisture damage to your walls over a long period of time.
Use moisture-resistant drywall to reconstruct the walls. This type of drywall will prevent long-term water damage.
Decide on the finish you would like for your steam room. Ceramic tile or glass are both very effective waterproof finishes, and they should be placed over the moisture-resistant drywall all around the room.
Seal the edges of all walls, windows and other connection points with silicone . Silicone is waterproof and will prevent moisture from entering your drywall.
Ensure you have proper airflow and drainage points. A small gap under the door of a steam room will allow fresh air into the room, and drains are needed anywhere the floor tends to collect water.
For best results, you will want to consider constructing a slanted ceiling for your steam room. This prevents moisture from building up and dripping on people. A slant of 2 inches per foot is the recommended angle.