So, my carpenter friend and I have pretty much finished the 3 story rabbit condo for Boon and Phenom when they ar ready to move in together. They already love each other, Boon just needs his neuter in a couple of weeks. Because he is a carpenter, my friend made the structure primarily out of (safe, high quality aspen pine) wood, and then created tongue-in-groove slots to slide in the NIC cubes. The condo also has a peaked roof with shingles and a wind vane for decoration as it is an indoor condo.

However, since the structure itself is primarily made of wood, are there any great tricks or materials I can try to line these wooden areas with to chew-proof them?

Wish I had a photo, but the condo is in the carpenter friend's shop at the moment.

It sounds like an awesome condo! My biggest beefs with NIC condos are that they are messy looking and sometimes not very stable, but it sounds like both issues are addressed with your state of the art condo!

As far as the wood frame, there is likely to be some chewing, but hopefully it will be minimal "redecorating" and not affect the structural integrity of the condo. Is it put together in a way that certain pieces can be replaced as needed?  Maybe have your friend make a few spares now while he still has the measurements and equipment out?