I posted this in another thread, but I think it applies here too
My husband built a "mini coop" in the garage for the guys who are close to grown but really not there yet.
These guys below are all 4-6 weeks old. I know they look crowded but I assure you it's only because they all came running to the front because they thought I had treats
There are roosts, food and water in this "outside" part. The floor is open to the ground for when we take it outside, but right now it's on a tarp in the garage with pine shavings over it.
This is the "coop" portion with a roost and an additional feeder in case anyone is getting bullied and doesn't get a chance at the other feeder outside. The floor of the coop is ply with tarp stapled to it. When we move it outside we shoo all the girls into the coop and carry it out for the day. They come running when we open the door. At night we bring it back in and set it over the shavings.
The whole thing is probaby 4-5'x3'. The heat lamp doesn't really get used much anymore. I flip it on at night and the 4 weekers sleep under it while the older ones pick a roost in the house or elsewhere. We threw it together out of scraps.
I go out at least once a day and flip the the pen top up and lean it against the open coop top and they all play in the garage for a while. They stretch and fly and peck the floor and I usually hide some treats here and there for them to find while they're out.