I only have an interior for the garage. The large two story is stackable with a roof and a false floor, but because most of my models were so warped from age and general wear I found I really had to glue them to stay straight. My factory has braces inside to push the walls out to make it sit flat on the ground. I would love to do interiors, but the plasticvile buildings are really too small.
I used painted cardboard for the sidewalk. I founs when I added barrels and debris they turned out nicely.