If you are building a new facility, consider laying a concrete floor, and start the wall with one or two concrete blocks. This prevents rodents, snakes, and predators from digging under the walls and the floors. Windows and doors must be securely covered with heavy-gauge mesh wire or screening when opened. With outside runs, bury the wire along the pen border at least 30 cm deep, and toe the fence outward about 15 cm. This stops most predators from digging under the fence.
Animals always dig at the base of a fence.
By toeing the fence outward and burying it, the predator digs down right into more fencing. Some people run electric fencing around the outside of their pens 10 cm off the ground about 30 cm from the main fence to discourage predators. If your outside runs are not predator-proof, you need to lock up your poultry before dark. To prevent problems with hawks and owls, cover your outside runs with mesh wire or netting. Many times a 1 m grid over the pen constructed of boiling twine will give excellent protection from flying predators.