Cut the external damaged wall corner
Use a putty knife to do away with any wobbly material from the surface of the damaged wall corner. Now mark the affected area with a hacksaw and cut it in the vertical direction, using a taping or utility knife. Once you cut the damaged wall, use pry bar or screwdriver to remove all the screws or nails holding the plaster of wall in place – if any.
Install new corner bead
Install a good quality corner bead to avoid any kind of damages in future. Corner beads are available in the market in various shapes and sizes; select them according to your requirement and size of the damaged wall. Temporarily fasten one of the edges of the corner bead with the help of some drywall nails or screws. Now align the center of the corner with the attached corner bead and drive some more drywall nail into it. Carefully drive the inserted nails or screws flush with the surface of the wall of your house.
Apply joint compound
Use a putty knife to apply the very first coat of the joint compound to both sides of the wall’s corner, flaring the compound in the positions where it meets up with the surface of the wall. Smooth the surface of the joint compound with a taping knife and leave it for some time to dry well.
Apply second coat of joint compound
Once dry, simply sand out the affected wall on both sides with the help of sand paper or flat sanding block. Now apply the second coat of the joint compound. Wait for few minutes until the second coat of the compound dries completely. Apply the third coat of joint compound – if required. Paint the repaired Outside Wall Corner of your house.