I would locate them 12" from wall. Then do poop boards 24" deep, linoleum over plywood or osb. (scrape daily
) Make both roosts equal ht to avoid them fighting for higher roost. Do not get them too close to overhead rafters. Not good for chooks to roost overhead. (have to wear a raincoat and horatio hornblower/fisherman's hat to get eggs!
) Seriously tho, you don't want them pooping anywhere but over the poop boards for ease of cleaning. And you don't want them to be injured flying down from rafters.
For a look at poop boards and roosts, see 'My BYC Page' I think I am going to change my roosts to laid-flat 2 x 4's instead of the 2 x 2's I have now. I think it is easier on their feet and less likely for toes to get so cold in cold weather. I almost forgot to say that I store the poop in a large plastic tote bin with a lid that snaps into place. I dump it every 3 days on garden all winter long and on shrubs all summer long. It stores under the poop boards because they are 24" off of the floor. Also with the deep poop boards, the chooks can easily hop to roosts in two stages and if they want to they can hop down in two stages too. I set my nests at 24" ht also, while roosts are at 48" ht.