Can anyone give me some advice on how to better waterproof my nesting boxes? They extend out from the coop (with no roof over them) and are topped with tongue and groove pine. I tried some silicone caulking around the edges, that didn't work. Then I found some stick-on window flashing and that's helped a little, but they are still getting water in them when it rains. Frustrating! Can anyone suggest what material I can use and how to install it? I'm lost!