After removing a medicine cabinet from a bathroom wall, there will oftentimes be a large, rectangular hole left behind where the cabinet was recessed into the wall. While the size of this hole may make a do-it-yourself repair seem daunting, covering the hole is actually a simple repair job that requires only a few standard tools.
Use a drywall saw to cut out the top and bottom of the recessed area. To patch the hole, you will need to be able slip boards behind the edges of the drywall.
Cut two planks from the 1-by-3s that are at least 2.5 inches longer than the length of the rectangular hole. Place the first plank at one side of the rectangular hole and one plank on the other side. Position the boards so that each end overlaps the drywall by 1.25 of an inch. Screw both boards into place using drywall screws and a drill.
Trim a patch of drywall to the same size as the rectangle hole in the wall. Mark the height and width of the hole on the drywall, and use the drywall saw or a utility knife to cut the drywall to size.
Apply construction adhesive to the surface of the 1-by-3s and place the drywall into the hole, pressing it to the adhesive. Screw at least two screws into each side of the drywall and through the 1-by3s behind it to further secure it.
Cover the edges of the drywall patch with joint compound to fill in the cracks around the edges. Place paper tape over the joint compound to fully cover the joints between the patch and the wall.
Let the joint compound dry and sand the compound down until it is smooth to the touch. Cover the area with two more layers of drywall compound, letting it dry completely between coats.
Sand the final coat of joint compound lightly to get a smooth finish and apply paint that is the same color as the wall. Once the paint has completely dried, add a second coat of paint to fully conceal the patch.