Assuming you did not get bantam.
If you got medium sized chickens ~8"-10" of roosting space is plenty. If you got large, you're going to want 10"-12". And, if you plan to keep large tailed roosters, you need to be sure they have 18" of space between the roost and the wall.
Coop floor needs to be about 4sq ft as people have said; however, I do not use my coop like most do, so that number doesn't quite work for me. It's fairly flexible depending on how you intend to use your coop. Not sure where you are located...Here in deep south Texas, we hardly get a winter to speak of, and rarely get rain. So, our coops are more glorified roosts with attached nesting boxes than anything.
Our runs are quite spacious, though, because that's where the birds spend all their time. A minimum of 10sq ft per bird is good - more is better. If you have avian predators, do not fail to put a top on your run, or you will lose your flock to them. If you do put a top on your run - make it high enough up that you can walk in it...having to chase down and corner a chicken on your hands and knees through a chicken run is not an enjoyable experience.....just sayin' That's if you are going to use runs. We have predator issues, so we don't free range full time. That's something to consider. If you have land based predators, ensure that your run has about three feet high ½" hardware cloth. Higher than that can be basic chicken wire if you so desire. You also need to consider burrowing and digging predators. Be sure to bury that hardware cloth about 12" into the ground, if possible. We can't. We have very, very little soil before we hit limestone. But, we also don't have many burrowing predators, so it works out.
If you want areas in your run that are not turned into a moonscape, consider doing a 2"x2"x4" series of frames covered with hardware cloth and drive ground staples into the ground to hold them in place. You can put them up in various patterns and actually have quite an interesting effect in the run - it allows them to have areas they can dig down to dirt and enjoy their dust baths; but, it also allows green to grow up in the area and they will keep it short by eating it as it comes up through the wire.
When you build your coop, keep in mind that you need to clean it. Give that some thought. How often are you going to clean your coop? There are various methods that will make sense once you figure that out. Do you want to clean it every week? Every month? Every four months?
When you install the roosts, do so with the idea of cleaning in mind...nothing is more frustrating than having to fight your way around roosts to get to the floor so you can get the filthy litter up and get fresh down.
Give detailed thought to your weather patterns. Which way does the wind blow most often? How often do you get rain? How cold does it get? How hot? You need a lot of ventilation - plan it around those natural dynamics. Being able to put a good amount of ventilation under the eaves and on the non-winward side gives you an opportunity to provide a ton of ventilation without having to deal with a lot of rain blowing in or cold winds tearing through the coop.
Give thought to light. If you can, install a clear panel in the roof to provide natural light; and, if you need to extend your daylight hours because you want production to continue regularly through the winter, you may want to give thought to running electric out to the coop as well. Not a bad idea if you live in the northern climes where a heater is not necessarily a bad idea on the coldest days.
Give thought to where you intend to put the food and water. Many put it inside the coop, which is another reason the 4sq ft minimum is so popular. I don't. My feed and water supplies are outside the coop in the runs (we have too many predators for full time free range). Again - we rarely get rain...and, the last time we got snow, it melted when it landed on the ground and schools and places of business still shut down
So, we just have a covered area outside the coop that protects from the rare rain and spring winds where their food, grit and oyster shell sit. Their water is provided with nipples on piping that comes down from a 55 gallon drum with a float valve in it connected to piping that runs to our well....I don't like hauling water.
Consider the doors on your coop - are you going to be able to guarantee that someone will always be there to open and close the pop door? If not, you may want to consider an automated door. The other door you need to consider is
your door - again, thinking back to cleaning it out, and having to get in after a chicken for some reason. Make it comfortably wide enough that if you have something held under your arm, you can still enter and exit without complications.
Nesting boxes - you generally want one nesting box to every 3-4 chickens. They should be at least 12"x12". You really want the lid to be outside the coop for a couple of reasons - 1) ease of collecting the eggs and 2) keeping poop off the lids that would otherwise accumulate were they inside the coop. Additionally - be wise and be sure all of this stuff is in a place that is comfortable for you to access. Walk the area and find a location that works for you and then plot out your idea. Go through the motions a few times and see how they work for you. How do you naturally go to lift something? Make sure that the openings work with you, not against you.
Good luck and I hope they bring you much joy.
! I was wondering, is there a certain sq foot of nesting/roosting rule based on how many chickes you have? Do each chicken have to have their own nest to lay eggs?
