Walter is about 6 months old and is currently in a big plastic storage tub that you can buy anywhere (the ones you use to store decorations, etc) while his tortoise table is being remodeled. the tub works great to keep the heat and humidity up. I spray the enclosure down every morning and afternoon.
What can you use that is safe to treat the wood? I ran into the same problem when making my outdoor enclosure. I wanted to waterproof the wood or something but none of Home Depot's options seemed very tortoise friendly!