Coop design is huge, seriously. And building WAY larger than you think you need is highly advisable. When we got our first 4 and had them in a small pen, once we started letting them out in our backyard, it was SUCH a huge joy to watch them wander around the space available to them. After we got...
One of ours pops her head off to the side and she hauls full bore across a section of the yard LOL. And then they sound like little elephants with their feet pounding the ground! <3