I'm in the process of building my first chicken coop. It started with a large dog house which I bought from a neighbor. I got to thinking it was too small for the amount of birds I wanted and found I needed 4 square feet per bird. My current square footage will allow for six, but I would like to have 10. Since I have my coop raised about 3 feet off of the ground, can I add a lower level to increase my square footage? Also, does the area of the nesting boxes count when calculating square footage of the coop? Thank you for your help.