EDIT: Based on all the responses, which in a polite manner led me to believe I'd be a dumb**s for doing a flat roof, I went ahead and put in the trusses for a pitched roof. Thanks for helping me head off a mistake. See the pic below. I'm building a basic coop which is a little under 4x8. I'm trying to build as economically as possible so I designed the coop to use a single 4x8 sheet of plywood as the roof. It will be primed and painted. I also want a low profile so it is not visible above the fence line (suburban backyard). Has anyone else used a flat roof of this size and have you had any water issues? I'm assuming that with the small roof size and the fact that it probably won't be perfectly level, rain water will find a natural runoff point.