I am taking on the task to change my indoor enclosure, (Really, toss the old one out) And make a closed chamber. I have the design and everything down, my question I have is, how do I water proof the wood? Is it safe to use Thompsons water seal waterproofer on the inside? Or do I fandangle a way to put a tarp around the inside. Any waterproofing suggestions are most welcome, please and thank you.