I'm with you 100%! I bought this coop as an emergency measure. They say it will hold 15 full sized chickens. Well, they're lying. I got 22 in there at one point!
https://www.solwayrecycling.co.uk/shop/pig-poultry/hen-houses/standard-eco-hen-ark
Look, I'm not joking. There are 20 in this picture, some on floor some in nest boxes.
They all fitted in.

Not one of these chickens was forced to roost in this coop. In fact there were at the time two other coops, not as comfortable, they could have used. The roosting bickering was minimal as was the pecking of the hens on the floor by the hens on the roost bars.
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Before the fingers hit the keyboard this wasn't a situation I was happy with and it's not the situation now.
This is now. Five birds, six if you're fair about Henry's (rooster) giant backside.

There is four square feet per bird in this picture and the coop looks half empty.
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Years ago here in the UK the standard for free rangers was set by space on the roost bar, not the size of the coop and there's a problem right there. Going by roost bar space is fine if the chicken have hopefully a very large run they can access from dawn to dusk. They just use the coops for sleeping and egg laying, unless you're Henry of course who slips of to bed early to get a bit of peace before the hens start bickering about who sleeps where.
Now this is the UK and the climate, I'm led to believe, is moderate so the chickens where I am do come out every day into a run from dawn to dusk and later onto an acre of field for a couple of hours.
If one lives in more extreme climates and one may feel the need to confine chickens to a coop, then I haven't see anything on the market that I consider gives adequate space for maybe months of confinement and the reality is one shouldn't even be looking at these prefab coops in such circumstances.
I think the majority of the prefab coops get bought by urban chicken keepers with perhaps three or four hens which are part pets, part egg supply and most have runs
The manufactures are not lying. They say a particular coop will hold so many hens and all those I've seen do exactly that. The manufactures do not say you can keep that many hens permenantly confined in such a space. That responsibility lies with the keeper.
Any legislation, say four square feet per bird in the coop and ten square feet in the run is still woefully inadequate in run size but okay for birds that get out every day. Push that out to ten square feet per bird in the coop and an awful lot of people are not going to want to keep backyard chickens because they won't have a backyard left.
I'm not saying this is a good or bad thing, but it is a thing and if some governmet agency made a law (for the chickens welfare of course

) that one had to have ten square feet per bird in the coop and say three hundered square feet in the run, then that's pretty much goodby to urban chicken keeping.