Well Joan asked so here are my ideas on and undergound chicken house and I hope large barn too someday. I want it about 400 square feet, Keep changing my mind about the shape, if it should be square or rectangle, the people door is a challenge to fit in because we are almost flat where the buildings need to go even though the farm itself is on a hill. I am thinking a bulkhead door like for storm cellars with a counter balance, Installed to match the outside slope of soil line after it is back filled and buried. I am currently thinking to dig out about 3 ft, put in drainage (crushed rock) around the edge and away to the down hill side, build a post, shoring, poly, type structure, and bury it with the soil that was dug out from the hole to start with, I like the idea of a center pole bulding but that may be too hard to do, my next favorite style is a clerestory/shed roof style, with windows to the south. I think vinyl flooring would keep the chickens from digging inside, and block some moisture from coming up through the floor, deep bedding is a must of course. It will also protect the floor level from the digging out that happens with dirt floors when they are cleaned, (each time you scrape the floor clean it gets lower than the original level, and soon you get puddle spots) I probably will not decide until we are out there digging the hole exactly how to do it, I am really bad about doing things that way. I am open to ideas from out there too!