Garage coop.

[Jenilynchickmom]

We have. 4x8 roost/coop in our garage. There is an automatic door that opens out into a covered run. Our girls have been in here about 2 weeks so far

 

[Compost King]

or yours will become covered in thick dust.

I can confirm this will happen, I knew it would happen but I had no idea the dust would be an inch thick in one year. No problem in my situation since it was a storage shed and everything stored could hand dust. Your drawing show you have ventilation issues handled. It looks professional too. I like the idea of using an existing roof to build a coop.