From personal experience in using wood to build an enclosure make sure whatever you use to seal will stand up to the test of time and extended exposure to water. Of course it depends on the climate you live in as well. If humidity is able to be maintained easily it's less of an issue. I live in a more arid climate so I have to mist more and the wooden cages I had built did stand up well, but had minor issues. In particular, polyurethane doesn't do well with standing water, mind you I think I used a water based version. Basically if you use wood, make sure you avoid water standing anywhere.