When we put our coop together we plunked it down on top of a solid sheet of 1/4" hardware cloth with a 1ft apron all the way around before adding the footing. I just saw a Mink hit on the road not a mile from my house and realized there are so many places they can get in! The corrugated roof has huge egg-sized gaps both in the run and the house. Since the roof is plastic and the frame is metal there's no good way I can see to fasten hardware cloth to the top. I have heard that mice and rats can't chew through polyurethane foam, would it stop a mink or a weasel too? The chicken house also has large gaps in the floor that I've been meaning to fill with something, but it's in the corners so fitting in hardware cloth and having places to fully attach it will be tricky.