Before I built my coop and run I read on here that you needed 2-3square feet per bird in the coop and 4-5 square feet in the run. I will not free range my birds ever again do to past bad experiences! So my run had to be built to hold 20 birds. Now I come here and read 10 Square feet per bird? I am thinking back when my grandma had chickens they stayed in the same run and were not moved around, nothing fancy and they had less room than mine do know. And her chickens seemed healthy and happy enough. If my grandma was to see my coop she would tell me it was to fancy for some ole chickens! RIP grandma I still miss you and your fried chicken! So I am going to stick with the 4-5 Square feet per bird. Grandma raised her chickens for eggs and meat. I am just raising them for eggs mostly. 4-5 square feet in a totally enclosed pen,with hardware cloth is working fine for me and my 11 golden comets that are laying right now and I have 5 in the brooder that will be joining them soon. Oh and I have sand in my coop and in my run easy clean up!