I went ahead and sealed the inside with a urethane sealer, then glued white plastic shower surround material on the bottom, sides, and back. I am going to place my heaters between that and tile. I also wired three lights that I will connect to a dimmer. These will be protected by a screened frame. The entire cage is oak, except for the back pieces, which is pine plywood. I have sealed it with urethane and then covered it with the plastic. Hopefully that will not be a problem?