coop: approx. 10x20
the trick to saving money is to use what you have on hand. I had some extra 8' 2x4's and 12' 2x4's, so I made a 20' long building with one of the center posts offset 4' so I utilized the wood on hand. It's not symmetrical but it's strong. Remember it's a chicken coop not a garage. The window on the far end was a new yard sale $5 special, double hung with screen. The windows on the front south-east side are from a Chevy Astro-van. Yes they open and close. The siding is Adirondack siding leftovers which were 100% free from my neighbor. The posts are pressure treated 4x4's and I used OSB sheathing and shingles for the roof. Steel would have been cheaper. The floors and the rest of the wood are rough cut bargain specials from the local sawmill. This 10x20 building including the nest boxes and roosting shelf with a 12/12 pitch shingled roof cost me about $700 total including the nails, tar paper underlay, everything. If I used pre-built trusses and a metal roof I could have saved $100 or more. I set the rafters 16" on center I could have put them 24-36" and saved even more. I could have left a dirt floor and saved another $150. I overbuilt this thing to withstand yak attacks and to hold up to blizzard conditions. I have seen people build chicken coops with used pallets and a truck cap.