We built our coop, but we caulked up the seam between the nesting boxes and the wall of the coop, and then we added a strip of the rubber molding that they use in schools and such as baseboard. It was the perfect width, and we used two pieces so together they were long enough. We caulked the heck under it, and screwed it on. The rubber is actually the hinge on our nesting box lid. It works great! Just an idea.