A key skill in drywall repair is how to fix overcuts. Overcuts are those drywall holes that end up being noticeably larger than the fixture on top of them. Follow the steps below to make invisible repairs to drywall overcuts.
Determine the Exact Hole Size
Measure to get the exact hole size. If it is less than 2 inches beyond the switch faceplate or outlet cover, you can tape the edges and coat them thinly with drywall mud. If it is larger, you will need to make a base out of drywall mesh first, and cover it with tape, then with drywall mud.
Repair a Hole 2 Inches or Smaller
Measure carefully where the visible edge of the hole will be. Trim the raw edge with the utility knife. Mix drywall mud in the mud pan, using the drywall mixer wand and drill, so it matches the surface texture. Spread the drywall mud over the edge of the hole, and about 1/4 inch beyond the hole's visible edge. Apply drywall tape, cut neatly and squarely, all around the hole edge.
Make minimal overlaps with the drywall tape to prevent ridging. Apply more drywall mud over the tape, and smooth it out with a flat drywall knife. Keep blending and smoothing till the visible edge is blended into the existing wall surface. Allow the drywall mud compound to dry for at least 2 hours, or till it is snowy white. Sand the patched edge well with the fine-grit sandpaper, mounted on a palm holder to prevent scratches. Wipe off the sandpaper dust with a dry cloth, then a slightly damp cloth to remove as much as possible.
Prepare a Large Hole for Repair
Cut a drywall patch for the inside of the hole, to the size of the light fixture support, light switch, or outlets. Measure and cut the amount of drywall mesh you will need to cover the entire hole including the patch, extending it 1/2 inch beyond the visible edge of the hole on all sides. Trim the edges of the hole so they are neat and thin, to help the patch and mesh adhere better.
Apply the Patch and Drywall Mesh
Fit the patch into the hole and seal it in with drywall mud. Peel the backing from the self-adhesive drywall mesh and press it carefully over the patch and hole, around the open edge, using even, firm pressure so you do not dislodge the patch.
Mud Over the Patched Hole
Put drywall mud evenly over the patched hole, and smooth it with a drywall knife. Allow the mud to dry for about 20 minutes, then tape over the outer edges of the drywall mesh. Apply a coat of drywall mud evenly over the tape, so the taped edges are concealed. When the compound is dry, sand smooth with fine-grit #200 sandpaper.