Someone gave me an old doghouse to convert into a coop. I tore it down to the frame, which measures 30" x 35". If I put the roof back on it would be about 24" tall inside. I plan on having 3 hens. Too small, yes? I was thinking I'd add 2 more box frames to the design before closing it in: one on the side to increase sq. footage, one on top to add height for roosting. Everything I've read on space merely deals in sq. footage. I'd like to know how deep the inside needs to be. Is 35" inches deep good enough if the coop is long enough to provide appropriate sq. footage? And how high do the chickens need at a reasonable minimum? I can't work in ideals here, as my coop must be built from salvaged/donated materials, but I don't want to punish the birds. Additional Info: I plan on making a waterer with pvc pipe and the nipple-style drippers, with the reservoir outside, so that will take up less interior space. Nesting box will be an add-on, not taking up interior square footage. The coop will be attached to a run that I plan on being about 4' x 8'. The hens will free range while I'm outside and in the kitchen, 1-4 hours a day.