Hello, we converted 12x12 horse stalls into chicken coops. They were built with three walls and galvanized tin. Along the inside of the walls, we took a grubbing hoe and dug out a narrow trench about 4" wide and 12" deep along the base of the walls. In some areas we poured concrete, other areas we buried 2"x4" horse wire and other areas we buried rocks. Anything you can place in the ground to keep predators out will work. Along the open front we paced a 12' 2x6 along the floor and poured concrete about 4" thick and about 12" inches below the ground. From the new 2x6 with concrete, we built a new wall that included chicken wire and a walk through door.Since we converted the horse stalls more than three years ago, we haven't had any trouble with predators digging in. Good Luck!!!