Headspace above Roosting bar?

[Badchickenpun]

I am designing a small chicken tractor that is doubling as a hospital and new chicken introduction cage.
I have the design most done. The frame is mostly built.
I am working on the coop part, now. I am debating between a double pitch and single pitch roof.
I need to know how much headspace would you recommend above a roosting bar?
This is not for long term housing, but temporary, for injured, new and young hens.
The current hospital pen does not have a roosting bar and the injured chicken is not happy about it... LOL

 

[perkolator]

I'd go for something like 18" which should be fine for most breeds. You'll want enough head room for them to jump up there and flap some wings without hitting the ceiling

 

[3KillerBs]

A foot below the upper-level ventilation.

They need to have their heads down out of any possible drafts when they're sitting on the roost.

 

[rosemarythyme]

They can fit with about 12" to spare above, but assuming there's ventilation up high you want the roost about 12" or more under where any drafts might be.

 

[aart]

I need to know how much headspace would you recommend above a roosting bar?

Headspace being the space above their heads when on the roost.
So I'd say at least 24".

 

[Krugerrand]

Lots of answers already. I keep @Yakisugi Coop 's article handy.
https://www.backyardchickens.com/articles/yakisugi-coop.76398/

You may reach different conclusions, but it's a treasure trove of resources.

The article references this site's vote for 18":
https://www.thefeatherbrain.com/blog/how-tall-should-a-chicken-coop-be