Ok, I'm not representing myself as an expert or anything, and if you see where I've gone wrong let me know but...
With my Coop house the chickens have just over 2 Ft. per bird.
I can't see why they would need anymore then this, at least in my area of the world.
My chickens go in their house twice per day, once to lay an egg and the other to go to sleep.
The only exception to this is when I stick my camera in their coop at night and flash them, then they arn't sleeping
I couldnt get everthing into one shot from their clean out door but, the four older girls are sleeping in the corner against the far wall and the two younger ones are trying to sleep to the left.
With the way they pack themselves into one spot, there is enough room for another 7 chickens in there.
I dont think they would be happy with another seven chickens but there is alot of roost space thats not taken up.
I orignally planned the house for 3-4 chickens, but it seemed to me there was plenty of room for more so we added the other two.
Their outdoor run has a minimum of 10 sq ft. per bird, its really larger but, it also changes around a bit.
Ok that went longer then I wanted.
So, the question or answer is, what am I missing?
If nothing, I guess my point is that, there are no hard and fast rules.
I have 3 hens who share a 6sq foot house.
As with Barg's birds, they only go in there twice a day, once to lay and once to sleep. They have 10 inches of roosting space each, but all tend to huddle up one end.
As it's getting light so early in the morning and the weather is warm (yes, even in the UK) I leave their pop door open.
During day light hours they have use of a run which gives them around 10sq foot each. I let them have the run of the yard (unfortunately it's concreted) for a couple of hours a day when I get home from work.
Ideally I'd like to give them more space, but they seem to be three happy hens anyway. They lay well and are lively and VERY talkative.