Have you read my article on
Deep Bedding? I focused on small coops, but the principles scale.
A lot depends on what kind of floor you're going to have. A dirt floor favors the actively-composting Deep Litter system, a solid floor favors Deep Bedding.
BIG roof overhangs and correct orientation of the solid walls are key to keeping the interior dry for an Open Air coop if you're going the Deep Bedding direction.
I wonder if, given your location, your local Habitat ReStore might have old Jalousie Windows? Offering a free flow of air while keeping the rain out is what they were designed for back in the days before air conditioning existed.
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Back them with hardware cloth and blowing rain isn't much of a problem anymore -- though it would cost more.
There are also top-hinged windows:
https://www.backyardchickens.com/articles/window-support-for-top-hinged-windows.74810/
Because smaller structures are easier to build (you may need a building permit for a structure that large -- 24x24 is larger than a 2-car garage).
Because they want to control the breeding, pairing specific hens with specific roosters.
Because roosters often do not get along even when we think that they *ought* to. A rooster doesn't naturally think "It's OK for him to have those 10 hens because I have my 10 hens." He thinks "All the hens are MINE." It's called "cockfighting" for a reason.
Because it's easier to keep track of the health and welfare of a flock that's been divided into smaller groups. In a vast crowd it's easy to overlook a bird that is sick or even missing. When you have them in set groups you notice if Pen A is short 2 hens or one of the birds in Pen C is limping.
Because if you're seriously into production you'll want to cycle your flock by age -- replacing hens and roosters on a schedule to maintain peak productivity.
Right.
There is no one-size-fits-all method for raising chickens.