I second the air flow problem. However, I think there's something else that no one has mentioned. That is, in my experience the deep litter method will not work in that small of a coop, especially with the amount of chickens you have in there. Please correct me if I'm wrong, but I've read somewhere that there's just too much poo per square foot or something, and usually not enough air flow.
You need quite a substantial amount of bedding to do this method and I've found it works in my coop, but it's 10 x 14 feet with only 8 birds. I previously had ducks in there, too, and I'll tell you ducks are just too messy for that method.
If your coop is only 4x5 or some such, I'd just clean it out on a regular basis and compost the litter for the garden. Be sure to wait a year so any pathogens in the litter will be killed before putting it on the garden.
