Our chicken coop is raised off the ground about 2 feet to keep snakes, rats and other such critters away from the hens, eggs and chicks. We did an installation of an permanent electric fence to close the coop off from any outside predators such as dogs, bobcats or coyotes (depending on your area). Our fence is 5 feet high to prevent any predators jumping over and was purchased from
http://www.zarebasystems.com. Be sure to train your birds correctly and immediately to return to the chicken house every night to prevent any stragglers from roaming around at night, doing so will attract predators to your coop.
