Both Bertie and Mercedes love to chew. They chew up the vinyl floor in their room. They particularly love the texture of cardboard on their teeth. Anything cardboard does not have a long life if they can access it. One bun tunnel's floor didn't last a week until it was so "renovated" that the sides caved in. In these pictures you can see what is left of the top of a maze haven--it was a single story construction--in order to satisfy the need to chew the buns had to get on top of the structure and chew it out from under their feet. The same with the remnants of the bun fort which used to have connecting tunnels with floors, once the floors were gone, the tunnels collapsed, so the buns moved on to the rooftops. They are about due for cardboard replacements, or maybe I'll find them some phone books like Silver's person does. Personally I think their ears have been picking up tv signals from DIY shows, and the renovation phases are what they're channeling, they certainly haven't built anything.
Bertie in the ruins of his fort, waiting for privacy so he can resume working on the roof
What is left of a Maze Haven