Roosts should be at least 12" away from wall...18" is better.
Something else to consider:
There's a 'stack up' aspect to coop design:
Bottom of pop door should be about 8" above floor so bedding doesn't get dragged out of coop.
Nice to have bottom of nests about 18" above bedding to allow use of that floor space under them(doesn't count if your nests are mounted on outside of coop).
Roosts should be about 12" higher than nests so birds won't roost(sleep) in nests and poop in them.
Upper venting should be as high as possible above roosts so no strong drafts hit roosts in winter...and hot/moist air and ammonia can rise and exit coop.
Something else to consider:
There's a 'stack up' aspect to coop design:
Bottom of pop door should be about 8" above floor so bedding doesn't get dragged out of coop.
Nice to have bottom of nests about 18" above bedding to allow use of that floor space under them(doesn't count if your nests are mounted on outside of coop).
Roosts should be about 12" higher than nests so birds won't roost(sleep) in nests and poop in them.
Upper venting should be as high as possible above roosts so no strong drafts hit roosts in winter...and hot/moist air and ammonia can rise and exit coop.