What size coop for tiny chickens?

[MROO]

I think I would like to have 4 hens and one roo. Is that enough hens for one roo?
I Know a lot more about Ducks and geese and large chickens then I do about little bantams.

My big chickens are chocolate English Orpington and I just have 3 with no roo. They have a a 4x4 raised very sturdy house and about 1500 sq feet run. And they’ve been doing great.
I keep them separate from anyone else in the yard they used to be with my Ducks, but they were mean to them ( 3 chickens terrorized 21 ducks)

Now I have my ducks split into two flocks because I have two drakes, and I don’t want to risk them ganging up on any female and drowning her. They are father and son. The father has four girls with him in their own yard and their own coop. The son Drake has all the other ladies in about 3000 sq foot yard with many many obstacles, hiding places, bushes, shady trees, etc.
I’ve had my ducks over 10 years and five of them now are over 10 years old.

And my 3 goose family, of course, has their own yard and house because they like to eat grass, and if the ducks were allowed over there, the grass would be wrecked.

Bantams are a whole new world to me. I have a private run already for them that’s about 450 sq feet.
There is a little children’s Playhouse already in there but it’s one of those plastic ones and I don’t wanna convert that.
I’d like to build them a 4 x 4 raised house like my other chickens have in their area.
I thought that perhaps since my 3 very big chickens do well in theirs that 5 tiny ones would be happy in the same size building?

I LOVE my playhouse coop! It's a full-sized wooden playhouse with a "sandbox" underneath as a run, so it's big. It's really more like a raised wooden shed. It was super easy to convert. Check your local "Craig's List" or Freecycle type listings for someone looking to get rid of one. They're often free if you move them yourself. If you're handy at all, prefab wooden playhouse kits aren't terribly expensive - and some of them are really cute!