Well I'm actually building a bigger one than you are right now and you can buy non-toxic sealent to cover up the wood or mod podge. Its what I use to cover my styrofoam wall, hide and waterfall. Or just glue some plastic siding to the inside of the wood and use cocking to seal it. No wood can be exposed not just for your snakes safety but the wood will be destryed by the humidity and fall apart. If you need to know more you can see pics in my profle threads or I can send you some updated ones tomorrow. Or if you just need help ith how to make it safe let me know and I would be happy to help.