This is an old thread but still a good topic. We keep chickens in so many different conditions, in different climates, with different flock make-ups, bantam versus full-sized, with different goals, using different management techniques, and so many other differences that no one magic number is going to cover us all. We’ll even have different definitions of “need” as you imply with your commercial versus happy chickens comment. The recommendations or guidelines are reasonable starting points for those that have no experience with chickens, but you get different suggestions for that depending on who you talk to. It’s not necessarily how much space in the coop that is important as how much total space in the coop, coop and run, or whatever that is available when they are awake.
Most of those recommendations will keep most people out of trouble under a lot of different conditions and are maybe overkill for some of us, but I find the more room I can give them the fewer behavioral problems I have to deal with, the less hard I have to work, and the more flexibility I have to deal with things that happen.
I haven’t posted this for a while, but I’ll post something I wrote a few years back about why we might have different needs for space for chickens. You might find it interesting.
I don’t believe in magic numbers for chickens. We keep them in so many different conditions, in different climates, with different flock make-ups, and use so many different management techniques that no one magic number will cover us all. Some of the things that make up the space requirement are, in my opinion:
1. Personal space for the birds. They have different personalities and different individual requirements. Some are very possessive of personal space and some can share. Each flock has its own dynamics.
2. Access to feeder and waterer.
3. Being able to put the feeder and waterer where they will not poop in it when they roost.
4. Roost space. They not only need to have enough room to sleep on the roost, they need to have enough room for them to spread their wings and fly to the roost and to sort out who gets to sleep next to whom and who gets the prime spots once they get on the roost. When they get on, they may jump from some midway support or fly directly to the roost, but either way, they like to spread their wings. And some chickens seem to enjoy blocking the entry points if there are limits. And when they get off, mine tend to want to fly down, not jump to a halfway point. They need room to fly down without bumping into feeders, waterers, nesting boxes, or a wall.
5. Poop load. The larger area they have the less often you have to actively manage the poop. They poop a lot while on the roost so you may have to give that area special consideration, but mucking out the entire coop can be backbreaking work plus you have to have some place to put all that bedding and poop. In my opinion, totally cleaning out the coop is something that needs to happen as seldom as possible.
6. How often are they able to get out of the coop? The more they are confined to the coop, the larger the personal space needs to be. The normal recommendation on this forum is 4 square feet per full sized chicken with a minimum of 10 square feet of run per bird. This additional requirement outside is sometimes not mentioned. How often they are allowed out of the coop may depend on a lot more than just weather. Your work schedule, when you are able to turn them loose, what time of day you open the pop door to let them out or lock them up at night, all this and more enters into the equation. The 4 square feet recommendation assumes they will spend extended time in the coop and not be able to get in the run. What that extended time can safely be depends on a lot of different factor so there is no one correct length of time for everyone.
7. Do you feed and water in the coop or outside. The more they are outside, the less pressure on the size of the coop.
8. The size of the chicken. Bantams require less room than full sized chickens. This has to be tempered by breed and the individual personalities. Some bantams can be more protective of personal space than others, but this is also true of full sized breeds. Young chicks need less space than mature adults.
9. The breed of the chicken. Some handle confinement better than others.
10. The number of chickens. The greater the number of chickens, the more personal space they can have if the square foot per chicken stays constant. Let me explain. Assume each chicken occupies 1 square foot of space. If you have two chickens and 4 square feet per chicken, the two chickens occupy 2 square feet, which leaves 6 square feet for them to explore. If you have ten chickens with 4 square feet per chicken, each chicken has 30 unoccupied square feet to explore. A greater number also can give more space to position the feeders and waterers properly in relation to the roosts and provide access. In general the more chickens you have the less space per chicken you need. You are more likely to get in trouble with 4 square feet per chicken if you have very few chickens.
11. What is your flock make-up? A flock with more than one rooster may be more peaceful if it has more space. I don't want to start the argument about number or roosters here as I know more than one rooster can often peacefully coexist with a flock, but I firmly believe more space helps.
12. What is the maximum number of chickens you will have. Consider hatching chicks or bringing in replacements. Look down the road a bit.
13. Do you want a broody to raise chicks with the flock? A broody needs sufficient room to work with or you risk problems from other chickens.
14. The more space you have, the easier it is to integrate chickens. Chickens have developed a way to live together in a flock. It’s called the pecking order. But establishing that pecking order can be pretty violent. One method they use to take most of the danger out of establishing the pecking order is that the weaker runs away from the stronger when there is a confrontation or they just a void the stronger to start with. They need room to run away and avoid.
15. The more space you have the more flexibility you have dealing with problems.
I'm sure I am missing several components, but the point I'm trying to make is that we all have different conditions. There is no magic number that suits us all. The 4 square feet in a coop with 10 square feet in the run is a good rule of thumb that most of the time will keep us out of trouble, but not always. People starting out with no experience with chickens need a starting point. The 4 and 10 is a good starting point. For a lot of us it is more than they could possibly squeak by with but I do believe that more is better both in the coop and in the run.
There are also people that have no trouble with a lot less space. If the coop is used only for sleeping and maybe some nest boxes, you can get by with less. But there has to be additional space available when they are awake. If you commit to giving them that space whenever they are awake, you don’t sleep in any mornings and you have to find someone to let them out at the crack of dawn if you are away for a while.
It doesn’t matter if the space is in the coop, coop and run, or they free range and sleep in trees. It’s total space that counts, not just coop size in isolation.