We have a small tractor coop that our girls quickly outgrew. So, armed only with the idea of something 'bigger', we set out to build our own. Here is how it went:
Frame 2x4 with braces. 4' wide x 8' long x 5' 6" tall without wheels
Plywood sides, nest box and floor. Windows on three sides, full size door for us, wide double doors in back. We had lots of help as it was 'all hands (claws) on deck!'
As you can see, our girls moved in even before it was built. Hex wire, galvanized supports, hinges, latches, etc. Some paint along the way...
Here are more finished pictures and the small tractor that we outgrew:
It was a lot of work, but well worth it. We even had fun with it. Best wishes to all!