What is your climate like? how long will you have snow on the ground a year. Depending on your climate (and some other things but climate is probably the biggest factor) you could need anything from 7' x 8' to 15' x 15'
Climate is western middle tennessee not to bad. No major snow but a little dusting. Normally it doesn't get to cold 25 being the lowest at night and that doesn't last long. It's just temporary I'm gonna end up with 2 coops. Hubby is gonna build himself a big she'd and I am gonna convert our old she'd into a coop. One other question does it need a floor or can I just have a dirt floor and put straw down?