if you are considering replacing the coop, I recommend switching to a Green Frog recycled agric plastic one (not cheap, but holds its value so when you come to sell so you'll get your investment back) which has very few places for any creepy crawlies to hide, and is trivial to assemble, disassemble and blast with a power washer (so you save on cleaning chemicals, pesticides, or the hassle of trying to get hold of real creosote).