How to Replace Interior Drywall Corners

Scrape off the drywall mud covering the corner bead with a putty knife. Remove as much of the mud as possible to expose the screws or nails holding the corner bead in place.

Back out the screws that hold the corner bead in place, using a drill and a Phillips drill bit. If nails were used, grasp the nails' heads with pliers and pull them out. If you only want to replace a section of the corner, use tin snips to cut the corner bead at the desired height. Do not worry about damaging the section of drywall you plan to replace.

Run a stud finder over the wall to locate the nearby studs. It is easiest to remove drywall up to a stud. Mark each stud nearest the corner, on either side.

Place a level on the wall to use it as a straightedge. Draw a rectangle around the portion of drywall you wish to remove, on both sides of the corner. Cut out the rectangles with a drywall saw. With the drill and the Phillips drill bit, back out any screws you come across holding the drywall sheet to the studs.

Measure the two rectangles' lengths and widths. Transfer these measurements to a new piece of drywall. Use the level as a straightedge to connect the measurements. Cut out the rectangles with a drywall saw, or score the drywall's front surface with a utility knife, break the drywall along the scored line and cut through the paper backing.

Position one drywall rectangle in place. Secure it to the studs with drywall screws. Sink the drywall screws' heads slightly below the drywall's surface so you can easily cover them with mud. Repeat on the corner's other side.

Measure the length of corner bead you removed and cut a new piece to this length, with tin snips. Position the corner bead onto the corner, overlapping the two new drywall pieces. Secure the corner bead in place with drywall screws.

Place a piece of adhesive drywall tape over the gap between the old drywall and the new drywall. Pour drywall mud into a mud tray. Use a 6-inch mud knife to apply a thin layer of mud over the drywall tape. Make the mud layer as smooth and uniform as possible to cut back on sanding time later. Apply a layer of mud down the corner bead on either side of the corner. Allow the mud to fully dry.

Apply a second coat of drywall mud over the first coat. Use a 10-inch mud knife for this coat. Feather the edges of the mud by applying more pressure to the knife's outer edge. Make one pass above the tape and one pass below the tape to create a wide and feathered coat. Run a second coat over the corner bead's first coat. Feather the edges of this coat as well, away from the corner. Allow this layer to dry.

Sand the dried drywall mud with a sanding sponge. Remove as many ridges as possible. If necessary, apply a third coat of mud with the 10-inch knife, then allow this layer to dry and sand again. You can now prime, texture and paint the new corner drywall pieces.