Drywall and Plaster Crack Repair Tutorial

Repair wall and ceiling cracks in plaster or drywall using this method. This repair technique requires the use of setting–type joint compound. Using ready–mixed joint compound, spackle or other wall repair material may not work as well for this process.

Major plaster cracks caused by extremely loose and crumbling plaster can not be repaired using this technique alone. For most plaster cracks taping is an effective and permanent solution, however, if your plaster is cracking because it is loose, the lath and brown coat under the plaster coat must be stabilized to cure the cracking problem before crack repairs are made. See Repairing Loose Plaster for help.

Steps to Repairing Wall and Ceiling Cracks

• Clear debris from the crack
• Stabilize any movement that caused the crack
• Apply fiberglass mesh tape and mud over the crack
• Sand and paint

To repair a crack in any type of wall, the first step is to remove any loose material from the damaged area. With plaster cracks, there will be some loose sand and white coat and maybe peeling paint at the edges. Run a putty knife thru the crack several times to loosen any soft wall material and remove it. Scrape away any peeling paint.

Drywall cracks can appear along the edge of taped seams or corner bead as well as over doors and windows. Paper drywall tape may also bubble or it may be coming off completely. To prepare drywall cracks, use a sharp knife to cut bubbling and damaged paper tape away. Lightly run the tip of a putty knife thru cracks along the edge of drywall tape and corner bead to remove loose joint compound. Scrape off any loose wall material around the crack with the flat of a putty knife. Clear away all dust from scraping and prime the crack to prevent bubbling of the joint compound as the repair dries.

Bubbling may develop in the finished repair if contamination prevents bonding between the wall and joint compound. This is a common problem when water has damaged the cracking surface. If there's any contamination along the crack, sealing it with a shellac–based primer–sealer will insure that your repair efforts aren't wasted. You can use a spray can of sealer on lightly damaged surfaces. But brush primer on heavily damaged surfaces to be sure of good coverage. Let the sealer dry for 30 minutes to an hour before proceeding.

Before repairs, the crack will need reinforcement to stabilize it. For most cracks this is accomplished by applying fiberglass mesh tape but if the drywall or gypsum plaster around the crack is loose, further support is required. In some cased, it may be possible to drive screws into framing to reinforce construction and stop the movement. This is not always possible because framing studs and joists may be too far away from the crack to be of use. See Cure Recurring Cracks and Caulking Wall Cracks if screws won't work to stop wall movement.

Tape all cracks including exposed drywall seams with fiberglass mesh tape. This will reinforce the cracked surface for a lasting repair. See the Skim Coating Techniques page for detailed instructions for mixing and handling the setting–type joint compound used in this repair.

Apply a thick coat of mud over the tape. Cover the tape well, while pressing mud into the crack and the fibers of the tape. Cover a few feet of tape with mud and skim off the excess.

Hold the joint knife at about a 30 degree angle, press down firmly while drawing the blade along the tape to remove the excess mud. Avoid using too much pressure that would dig into the fibers of the tape. Leave a thin coat of mud over the tape and surrounding wall. Return the excess mud to the rim of the pan after each stroke of the knife to keep the blade clean.

Don't try to hide the tape with the first coat of mud. It will require a few more to cover the tape and smooth out the wall. Allow the first coat of mud to set for about 30 minutes and use 120 grit medium sandpaper to lightly sand the raised tape fibers. Avoid using too much pressure on the sandpaper which will dig into the tape. Also lightly sand the edges of the repair area to remove any excess mud.

Skim coat the crack until the texture of the tape is no longer detectable. This may take 3 or 4 coats of mud in some cases. Allow each coat to set for about 30 minutes. When you have completely covered the tape with mud, allow the final coat to set and dry for at least an hour. Sand lightly to smooth the surface of the repair and feather the edges into the surrounding wall. Brush any dust from the area and wipe lightly with a damp cloth before priming and painting. If you are using flat latex finish paint, you can use it to prime the repair. If you are using semi–gloss or other shiny paint, prime with flat latex or a latex primer first.