DIY Repair Wall Cracks

• Repair Bubbling Drywall Tape
• Caulking Wall Cracks
• Fill Cracks with Foam Insulation
• Skim Coating Techniques

This process can be used to repair wall and ceiling cracks in plaster or drywall but to repair bubbling or loose drywall tape use the process on the next page. Use setting–type joint compound for these crack repairs. 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 problem, before crack repairs are made. See Repairing Loose Plaster, Repairing Broken Plaster Key for help.

Clear the Crack

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. Lightly run the tip of a putty knife through these cracks 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.

Tape the Crack

Before repairs, the crack will need reinforcement to stabilize it. For most cracks this is accomplished by applying fiberglass mesh tape. Cut the tape as needed to follow the crack. Overlap the ends of each piece by a half inch or so.

If 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. Try filling cracks with foam insulation or caulking wall cracks if screws won't work to stop wall movement.

Cover the Tape with Mud

Use the instructions at this link to mix and handle the setting–type joint compound for this repair. Apply a thick coat over the tape with back and forth strokes. 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 then go back and skim off the excess to leave a thin coat over the tape.

Skim Off the Mud

Hold the joint knife at about 30° and 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 but enough to leave only a thin coat of mud over the tape and surrounding wall. Don't try to hide the tape with the first coat of mud. It will require a few more to cover the fibers and smooth out the wall.

Allow the first coat of mud to set for about 30 minutes and use 120 grit medium sandpaper to very lightly sand off the raised tape fibers. Also lightly sand the edges of the repair area to remove any excess mud.

Finish the Repair

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 with 120 sandpaper to smooth over the crack 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.