Yeah we've got a comercial style rug right there now, (entrance door to the shack) the type with the rubber back, it catches & holds water so it don't just soak into the plywood floor there.
but yeah a little rhino liner in that area would be a good idea.
No reply from wife yet on question of the "divorced" sauna.
If I told her she could have an outdoor hot tub that way too.... well then maybe....
