Sealing Wood

[GI Joe]

I'm getting ready to build an enclosure. I'll be using Oak for the wood. I want it to be furniture quality as it will be in my office. I want to know how to seal the inside wood against moisture.

Over the wood I will be building fake rock walls out of bondo coated foam which has been carved. I just want to ensure that humidity that gets behind the rock (or the possible spill ect.) won't damage the wood.

Any other hints to build a dream enclosure will be welcomed. Dimensions will be 4' long by 2' deep by 2' high. It will have locking, sliding glass doors in the front.

Thanks
jeff.