Each grown bird needs at least 18" of space on the roosts.This is for large fowl. You might get by with 12-14" for bantams, bearing in mind that they tend to scrap more.Chickens are not missles. They need room to spread their wings to get on the roosts!
The coop plans I used called for 12 feet of roosting, made with 2x4s. What I didn't understand at the time was that they shouldn't be below the nesting boxes. These roosts are only 6 inches off the coop floor. They Never used them. They use the top of the nesting boxes, and that Sure isn't enough for 19 birds. Today I added 4 long tree branches in several directions in the coop. Adding about 16 feet of roosting space. I'm looking forward to how they use them tonight
