I am planning on getting a small flock of chickens this coming spring. I have a very large back pateo, all cement with creeping fig covered brick walls.I am planning on making my run about 8'x10x'8'. I am modifying a rabit hutch for my coup and still making plans to make the ground better for my flock, such a aking a dust box and a small area of boxed grass ( which I am pretty sure they will destroy lol). I also plan on purchasing a travel pen for them so I can take them to my friend's house which has a nice back yard once a week. Are there any health issues with a cement floor for the birds, I worry about their feet and beaks. Also, how may chickens should I put in such a small run?