You can never have a too big chicken house. Mine is 12' x 24'. Started out to be 10' x12' but DH figured out he could re-use the trusses from the old cotton gin on our property. So... my chicken house is 12' x 24 ft. with a small chicken wired section inside to house chicks away from grown chickens, yet let them be close to the other chickens so they integrate into the flock easier.
I also have a chicken wire divider down the middle. Two 6'x 8' doors on either end of the structure, with nesting boxes built on outside walls for easy cleaning and egg collecting. I also use the deep litter method inside. 8 in. of pine shavings, dusted with Seven dust and DE to keep down mites.
Outside run of electric poultry netting about 40' x 60'. Moveable aroundable. Woot! Woot! I have very healthy chickens.
I was going to start with ten chickens, I now have about 40. I am getting 20 chicks April 5 this year. I am totally addicted to chickens, I admit it.
It sure is nice to see them running toward you when you bring them treats, hearing them sing the egg song in the mornings, eat those lovely large brown eggs for breakfast, lunch or dinner.
Be warned, people on this site will encourage you to have just "one more chicken."
You can never have too many chickens.
DonnaBelle