Even my heaviest hen (6 lbs) can easily jump 3 feet. No actual flying ability is needed for a chicken to get over that fence. The roosts in the coop are a bit too narrow for most brown egg layers. They need about 4 inch wide roosts. And you'll need at least 16 to 18 inches of roosting space per bird. Also, if the nest boxes are at the same height as the roosts, they may develop the bad habit of sleeping in the nest boxes instead of on the roosts. This will cause early morning eggs to be very, very dirty and gross. If space is an concern for you, avoid Easter Eggers. There is a huge size range for them since they aren't a standard breed. My smallest Easter Egger is maybe about 3 1/2 pounds. My biggest girl is over 6 pounds. The larger the bird, the less likely it will be to get over that fence. If you choose to go with a heavy breed, find a good breeder. Hatchery quality are usually much smaller than birds that meet the breed standard for size. A bigger breed will need a proportionally bigger coop and run, so you will have to keep fewer of them than other lighter breeds.