I just did my first coop too. It was a pain at first but looking around the boards at what other people posted and pics of other coops I figured it out pretty quick. Looks like you have a good start. The roof though looks like its a flat roof in the pics???? If you get snow I would say you need a sloped or pitched what ever you prefer saying. Just like on a house or barn so that the water and snow can slide off and not just pile up possibly damaging or all together caving in the structure. If you have any questions on other stuff for it I'll try to help ya out. I build cars but this was trying at times.... So just hit me up on the thread or pm and I'll lend ya some ideas! 
