We use about 5 gal. of water per person in the sauna. This accounts for splashing on the hot stones, washing and just dumping over your head when you get too hot. All this water has to go someplace and that place is a drain in the floor. Rustic saunas drain the water to the outside ground; we wanted a better solution so we connected the drain to to a gray water system. ( see bibliography at the end)Usually shower pans are built with a waterproof membrane, concrete, wire mesh and more concrete. None of this appealed to me as this shower pan would be almost 8' square not the standard 3' x 3' size. Moving all that concrete made me shutter. I had to find a better way.
What was needed was a very large funnel shaped floor. The slope would be 1/4" to every one foot of run. Than means that for every foot of travel the floor would slope down a quarter of an inch. Since the drain is in the center of the room the maximum distance is 4 feet. 1/2 of eight is four and four feet of travel is one inch. The drain in the center of the room would have to be one inch lower than the edges of the room.
The problem then was how to make this slope. I thought of using tapered screed boards but that meant that I would still have to lift tons of concreted and scrape the concrete to an angel. No good. Brainstorming, I drew radiating lines from the drain to the edges of the wall and what I saw was a bunch of pizza shapes. If I could make wide tapered pizza slices! I then remembered some work I had done years before. Using a hot wire a person can cut ridged foam insulation like it was butter. Hot wire cutting of ridged foam was the answer!
