First congratulations on July. That’s great news.
For a coop that size, you do not want it 4’ high. You need to be able to stand up in it. You do not want to be on your hands and knees every time you go in there and you will go in there.
While chickens are basically ground dwelling birds there are advantages to managing them to having more height to work with. They like to roost on the highest thing available. Whatever that is, it needs to be higher than your nests, noticeably higher. I don’t know where you will be located so I don’t know what kind of weather you are facing, but ventilation is important in both hot and cold weather. In hot weather you can’t have too much. In a really cold climate it’s often best to have wind protection where they are roosting but have it open over their heads. Having more height to work with makes that a whole lot easier.
I’ve read everything from 1 square foot per chicken to 16. Sometimes a run is mentioned, sometimes it’s not. I don’t believe in magic numbers for chickens. We keep them in so many different climates, use different management techniques, have different goals, just tremendous number of differences that there cannot be one number that works for all of us. About any of those square feet can work, depending on the conditions though even commercial operations don’t generally go as low as 1 square feet. That’s just too much even for them and their techniques.
You can follow the link in my signature to get some of my thoughts on space. A lot of that won’t apply to you but some will. I find the tighter I crowd them the more problems I have to deal with, the less flexibility I have to deal with that problem, and the harder I have to work. A lot of this is more for your benefit than the chickens. Why make your life harder than it has to be?
What you are talking about is basically what we call a tractor. You are providing predator protection but moving it around to provide fresh forage. I tried a tractor one summer. It did not last real long. I had 8 chickens in 64 square feet and had to move it every two to three days. It did not take them long to wipe out the vegetation and their poop quickly made a mess. If the ground was wet two days might be a stretch. If it was really dry, maybe I’d wait four days but I really shouldn’t have. It’s not just their poop but their scratching. I don’t know your climate or anything like that but you may find it has to be moved more often than every two weeks. If you move it regularly when needed you can get by with less room than with a fixed coop and run.
On that general note, it often helps if you put your location in your signature just so we have an idea about your climate.
What is your winter like? They won’t forage much if the ground is covered with snow. Something like this may be hard to move, say it freezes to the ground. A lot of people that use tractors use them in the summer to provide protected forage but have a permanent winter quarters, maybe greatly reducing the numbers in the winter and cranking back up in spring. Some of that depends on your goals.
If you haven’t considered it you might want to look at another model. Build a mobile coop but instead of a run use electric netting. You’ll need power but solar might work for you. Those pretty much stop any ground based predator. Birds of prey are still a danger. Some people have a lot more trouble with them than others. With electric netting you can give them a pretty big area to forage in and it’s not that hard to move. This model will be used a lot more for the number of chickens you are talking about than a mobile coop and run.
