I no longer have chickens but, when I did, their coop was built under the deck and the rest of the space under there was for them to be in if I wanted to keep them closed up. It was a very large area and I extended it out into the open so they could get some sun. They really loved it under there and scratched around until there was very little gravel but a lot of just plain dirt. They would make these deep dust bath holes and I was very thankful to have it for when there was bad weather or a hawk was hanging around or I had to go somewhere and lock them under the deck. I never had an issue with smell but, then, they would free range in my backyard when I was home so they didn't live under there 24/7. I kept their food under there during the day and it attracted chipmunks and rabbits but I didn't see any rats. Flies were present in the summer time but I used DE and that helped enormously. Soo, in my case, I thought it worked great!!