How to Repair Cracks in Plaster Walls: A Simple DIY Guide

 

Wall plaster, while sturdy and long-lasting, is prone to breaking over time. Fortunately, unless there is significant damage or underlying structural or moisture issues, crack restoration is a do-it-yourself project. You must first stabilize the plaster if it is crumbling or moving away from the wall. Once you're sure that the plaster is securely attached to the wall, you may go on to preparing the crack for repair.

 

Plaster Stabilization in the Surrounding Area

To see if the plaster has been removed, tap and press on the wall. All around the crack, press your fingertips against the plaster in a 1 ft (30 cm) radius. Make a mental note of any possible leaning spots against the wall. Tap your knuckles against the plaster in the same area as the fracture, listening for any hollow spots.

• ·        The plaster has split from the wood lath (horizontal strips of wood) that connects it to the wall studs, resulting in soft or hollow areas (vertical structural beams). Before the crack can be fixed, these detachable parts must be restored.
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• ·        Move on to cleaning and preparing the actual crack if the surrounding plaster is solidly in place with no trouble places.
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• ·        You'll need to repair any obvious damage around the fracture, such as crumbling plaster, which will require a new problem: fixing a hole in a plaster wall.

 

On both sides of the crack, drill pilot holes in the wood lath. Drill a hole in the plaster 1 in (2.5 cm) from the crack with a 1/8 in (3.2 mm) masonry bit in your drill. As you press through the plaster and into the wood lath, you should notice an increase in resistance. In reverse, spin the drill out of the pilot hole. On both sides of the crack, additional holes should be bored 3 in (7.6 cm) apart.

• ·        When you punch through the plaster, some of your pilot holes may travel into vacant areas between the strips of lath; in this case, there will be no resistance. Mark these holes with a pencil to avoid having to deal with screws.

 

Using drywall screws, fasten concave "plaster buttons" to the wood lath. Plaster buttons are a bowl-shaped plastic or metal disc used to secure plaster to the lath's backer. Insert a 1.25 in (3.2 cm) drywall screw into the hole in the middle of the button with the "bowl" facing upward. Completely insert the screw into one of the pilot holes, with the screw's head below the plaster surface.

• ·        Rep with the rest of the unidentified pilot holes.
• ·        Plaster buttons have a concave shape so that the head of the screw is hidden beneath the surface of the surrounding plaster when the repair is complete.
• ·        Plaster washers are a term that is related to "plaster button."

 

Check the plaster against the lath one last time to make sure it's secure. Press and tap the area around the crack once the screws and plaster buttons are in place. When you place it against the lath, it should feel solid. If it's still loose, the lath is probably ruined, and you'll have to perform more significant (and less DIY-friendly) repairs. This is without a doubt the finest time to hire a professional!

 

Crack Preparation and Cleaning

Enlarge the crack slightly with a knife to create a V-shaped groove. Cut straight into the crack with the tip of your utility knife or the corner of your tiny joint knife. To remove more plaster, run the knife along one side of the fissure at a 60-degree angle to the plaster surface. Rep the method to change the crack into a V-shaped channel on the other side that resembles a river valley.

• ·        A utility knife is a hand-held tool with a retractable blade. The blade of a joint knife is wide and flat, similar to that of a paint scraper. Joint knives come in a variety of widths for small, medium, and large joints.

 

Remove any loose plaster or dirt from the crack using a brush or vacuum. Sweep the inside of the V-shaped channel using a hand broom, paintbrush, or even an old toothbrush. Alternatively, suck up all the loose debris in the crack with a vacuum cleaner's hose attachment or a wet-dry vacuum.

• ·        This seemingly insignificant step should not be skipped! The patching material will not attach well to the existing plaster if you don't do this.

 

Coat the crack's surface lightly with a little amount of water. Spritz the crack and the plaster around it with a spray bottle half-filled with water. Wetting down the old plaster prevents the moisture in the fixing substance from evaporating too quickly.

• ·        Spray the area with a very diluted PVA drywall primer as an option. Combine 1 part PVA with 10 parts water in a spray bottle and lightly spritz it on. PVA may help the old plaster and repair material stick together.

 

Getting the Crack Fixed

With a little joint knife, firmly press joint compound into the crack. You can buy a pre-mixed container of joint compound or prepare your own by mixing the dry mix with water according to the manufacturer's directions because this is a minor project. Scoop a glob and press it into the crack with your joint knife until it is completely filled. Remove any large globs of extra compound from the crack's surface and the drywall surrounding it with a scraper, but leave a thin layer of compound on the crack's surface and the drywall surrounding it.

• ·        The consistency of joint compound (also known as drywall compound or "mud") should be similar to cake frosting.

 

If the crack is more than 14 in (6.4 mm) wide, cover it with fiberglass tape. Cut a single strip of fiberglass joint tape about 1 in (2.5 cm) longer than the crack on both sides for a fairly straight crack of at least this width. Use your joint knife to smooth it over the crack and adhere it to the wet joint compound you just applied. Cut numerous strands of tape to cover the crack in a single layer if the crack is more jagged; don't overlap the tape in any locations.

• ·        Skip the fiberglass tape if the crack is smaller than 14 in (6.4 mm) broad. Instead, wait 24 hours for the joint compound to cure before applying another layer.
• ·        Just a reminder: if you're taping over a crack, don't wait for the joint compound to dry—tape it while it's still wet.
• ·        If you like, you can use paper joint tape instead of fiberglass since it creates a stronger joint. For most DIYers, though, fiberglass tape is easier to work with.

 

With your little knife, apply a coat of joint compound to the tape. Smooth another scoop of joint compound over the whole surface of the fiberglass tape with your small joint knife. Begin at one end of the tape and spread the compound across the length of the tape in a single motion, then cover the remaining tape near where you started. Allow 12 in (1.3 cm) of compound on all sides to overlap the tape's edges, but scrape away any extra compound globs.

 

Apply a layer of joint compound using a larger knife after 24 hours. Scoop up some more joint compound with a medium-width joint knife. Apply it in a smooth, even coat, at least 1 inch over the previous application of joint compound on all sides (2.5 cm). By pushing a bit harder on the knife at the edges of the second layer, try delicately "feathering" the edges.

• ·        Instead of leaving a high edge that requires a lot of sanding to level out, feathering blends the joint compound into the surrounding plaster.
• ·        Yes, waiting 24 hours is challenging, but it's critical to let the previous coat of joint compound to dry completely before applying the next.

 

After another 24 hours, apply the last coat, feathering it out carefully. This time, use a broader joint knife to make the final layer at least 1 inch (2.5 cm) larger on all edges than the previous one. Work softly to level out the surface to the best of your ability. Apply a bit extra pressure to the knife as you approach each edge of the patching area to feather the edges of this layer.

• ·        It takes a lot of talent to apply wonderfully smooth layers of joint compound, especially when feathering it correctly. Don't worry if the results aren't perfect—all you have to do now is sand some more!

 

To blend the last layer into the wall, sand it once it has totally dried. Allow another 24 hours before beginning to sand. Sand any bumps, ridges, or high spots in the dried joint compound with a 120-grit sandpaper, applying even pressure and moving in circular motions. After that, sand the surface with 220-grit sandpaper to make it smooth. If the plaster around the repair is rough, skip the 220 paper to keep the repair from appearing excessively smooth.

 

Before priming and painting, sponge out any dust and allow the wall to dry. Simply dampen the sponge (or a cloth rag) until all of the sanding dust on the wall is collected. The repaired area is ready for priming and painting after roughly 15 minutes of drying time. Apply 1-2 coats of primer to the dried joint compound (any general-purpose primer will suffice).

• ·        If you want the mended area to disappear completely, you may need to paint the entire wall, but you might be able to get away with just painting the repaired area with color-matched paint.