My first coop was not a great coop. We built it using pallets for the frame, and sided it with garage siding. Now I didn't scrap the pallets and just use the wood, I used the pallets as they were for the walls. Fortunately I had some tall pallets at the time which made the wall height 5 feet tall, and then I build a peaked roof. The first section was 16 feet long and 4 feet wide, so narrow. But that's pallets. Once we out grew that I added 12 X 12 section behind that, this time with a flat roof. The coop had a dirt floor and it was pretty much impossible to rodents from getting in. It was cheap, and the coop despite the issues served us well. I guess if I had to say anything about that coop I learned what did and didn't work so well. Since then I have opened the long end of the wall and the old coop is now used for storage.
When we "built" the new coop we actually converted a two old pig sheds into the new coops. I should take some pictures. So one building is 15 X 10, the other second one is slightly smaller. The main things that had to happen is enclosing the walls of the sheds, putting in roosts and nesting boxes and building a run. I'd have to measure the run, but it's pretty big. This is a good solid setup that we are very happy with. The only thing I would do differently is back when I built these originally for pig sheds I did not put very much slope on the roofs. The current composition 2X4 frame, chip board, felt for a vapor barrier and then metal roofing on top of that. The problem is I have trouble with the seems wanting to leak because there is not enough slope. I've considered removing the metal roofing and going to a tar paper roof, but it's under heavy trees and I'm afraid winter storms would be pretty hard on tap paper. So I just seal seams as needed on the metal roof. The worst of the two I've coated with product made by Gardener for sealing metal roofs. It appears to be working pretty well but it's going to make removing the metal roof a real pain if I ever need to do that. Other than having to keep after the roof from time to time it's a really excellent coop. By the way it has a cement floor.