I have a 4' high fence of electrified poultry net around my coop. A 100X200' run. My birds don't go over that. I've read about people keeping them contained in 3' high fencing. But, depending on what breed of chicken you have, like Bantams or others, they may like to fly over anything. It is no mandatory that you have a covered run, mine seen to do quite well in an uncovered run.