My boxes are at floor-level, and I kept them closed off until a couple of weeks before my hens started to lay. The openings are 12" wide, 20" high. Since I have opened them up I have had no problems with pooping. In fact, they don't go in there at all, except to lay. I've tried to make the boxes an inviting place to lay by placing a 4" strip at the bottom and a 4" strip at the top, making a litlle 'hen cave'. Roosts are at least 2 feet above the floor.