Repair a Hole in Drywall

Although it’s far more easily installed than plaster, a surface sheathed in drywall (also known as sheetrock, wallboard, and plasterboard) tends to be softer and more damage-prone than one built up with plaster. The damage ranges from the small dents and scrapes caused by doors or furniture to major holes. Though it's unsightly, damage like this can typically be repaired by competent homeowners with the right tools and sufficient patience. Here’s a rough outline of how to patch drywall.

Evaluate the Damage

Determine the extent of the damage. Holes in walls can be of any size, but generally fall into a simple classification. The smallest class is the punctures made by nails or other picture hangers; next come those dents and scratches that don't break the surface. The third class is small holes that crack the wallboard and tear the paper - Many of these, for unknown reasons, seem to be fist-sized. Last comes large holes that might be caused by falling objects or trapped pets. You'll need to approach repair with different techniques and tools depending on the size of the hole.

Assemble Your Tools

Whatever the size of the hole, you’ll eventually use a putty knife or wallboard knife. Wallboard knives are made in widths of about 6-12 inches; for large holes you may need two or three sizes. No wallboard repair can be made without at least some joint compound. Although your college dorm roommate repaired nail holes with white toothpaste, a small container of joint compound or latex spackle actually costs less than that tube of toothpaste. Collect an assortment of different grits of closed-coat sandpaper. To repair a large hole you’ll need additional tools like a ruler, a wallboard saw, and something to use as a patch.

Repairing Nail Holes

Small holes caused by the nails used to hang pictures can often be left alone until you repaint the walls. While prepping for the paint, just press a bit of spackle or joint compound into the hole with your putty knife. Be sure to mound the patch a bit above the surface. Once the material is dry (check the packaging to see the recommended drying time), sand the stuff flat. Start with medium grit open-coat sandpaper and finish with fine grit paper.

Repairing Dents or Scrapes

As long as the paper cover of the wallboard isn't broken, repairing a dent or scrape just calls for a little joint compound. Lightly sand the surface first to rough up the paint, then fill the depression with joint compound. Use a 6-inch taping knife to smooth the goo. The patch will shrink as it dries. Allow your patch to dry for 24 hours before applying a second coat, if necessary. Sand the patch smooth with fine-grit sandpaper, and apply a finish to match the surroundings.

Repairing Small Holes

Drywall patch kits that will allow you to fill holes up to an inch or two across are widely available. Check the patch kit packaging for maximum size. Most kits consist of adhesive fiber mesh that you paste over the hole. Directions usually instruct you to cut a patch large enough to overlap the hole by an inch or so in all directions, then stick an adhesive patch directly over the hole or press the patch into a thin layer of joint compound. Always follow the package directions. Cover the new patch with several thin layers of joint compound, allowing the material to dry between layers. If you "feather" the edges of the compound with a broad taping knife, you can avoid avoid creating a "lump.” When the last layer of joint compound is dry, sand the patch smooth starting with a medium-grit sandpaper and finishing with a fine grit.

Repairing Hand-Sized Holes

Begin by drawing a rectangle that completely surrounds the hole. Use a wallboard (keyhole) saw to cut away the damaged section along the rectangle's outline. Cut a patch from scrap wallboard ⅛ inch smaller in length and width than the hole.
The new patch needs a backing strip: cut a length of lath or furring strip around 4 inches longer than the width of the hole. Fasten the backing strip to the back of the hole using a drywall screw driven through the wallboard and strip on each side of the hole. You may need two strips for larger holes. Spread drywall adhesive on the surface of the backing strip(s) and press the wallboard patch into the adhesive. Allow the adhesive to dry completely. 
Use joint tape and joint compound to seal the screws and the gaps around the patch. The process should take several applications over a few days to complete: patience is definitely a virtue when applying joint compound. When the taping job is complete, sand the patch smooth and finish the area to match the surroundings.

Repairing Large Holes

If you have a hole or break that's more than three or four inches across, You will need to expand on the technique used for smaller holes. Cut a rectangular opening that reaches from stud to stud. Attach a furring strip to the stud at both sides of the opening with screws or nails, making sure it's flush with the back of the surrounding drywall. These strips will form backing for your patch. Cut a patch from scrap wallboard ⅛ inch inch smaller than the opening in height and width, place it in the opening, and secure it to the strips with drywall screws. Use strips of joint tape and joint compound to fill the space around the patch. Once more, the joint compound will require multiple applications over several days, allowing it to dry completely between layers. When finished taping, sand the patch smooth and finish the new surface to match its surroundings.

If there is serious damage from settling or water, making repairs may require the removal of entire sheets of drywall or the removal of the bottom few feet of drywall where there has been water damage. The principles for larger projects are the same: remove the damaged wallboard, create a firm backing and a patch that fits properly, then complete the repair with joint tape and joint compound. Any underlying cause of damage should be treated first. If you are dealing with water damage, get professional advice for preventing mold and mildew within the wall(s) and take any necessary measures before you install a patch.

A Final Word

Regardless of the size of the patch, using joint compound on drywall calls for patience, both in applying the compound and in allowing it to dry between steps. If you rush the drying time, it can cause an unsightly patch job.