Tips for Repairing Cracks in Walls

Cracks on walls can be considered a charming irregularity that can add character to your home, but more often than not, it’s an eyesore that can really bother you. Eventually, even the best-built houses can develop a few cracks for many reasons. Generally, hairline cracks are caused by the natural settling of a house over time. They are usually easy to patch up using simple tools and materials, and you can easily do it on the weekend.

However, if the cracking is severe, this can pose a danger, and it may be the cause of structural problems or even signs of potential collapse. Large cracks are concerning, so you must have your home inspected by a qualified building professional and don’t repair the cracks yourself.

Here’s how you can repair small cracks on drywall, plaster, concrete, or brick walls:

Fixing a Drywall Crack

Some people think that it’s easier to replace entire portions of drywall with new pieces than to repair it. However, removing just the section that needs fixing and a few more inches beyond without needing to break down the entire wall is possible. Since drywall is made of one layer without backing, once you cut through it, there’s nothing behind it except for studs and insulation.

Tools and Materials Needed:

  • Utility knife or a 5-in-1 tool
  • Scissors
  • 6-inch drywall knife
  • Paper drywall tape
  • 150-grit sanding sponge or medium-grit sandpaper
  • Shop vacuum
  • Drywall joint compound
  • Mud pan
  • Painter’s tape

Instructions:

1. Cut through the crack

Using a utility knife or a painter’s 5-in-1 tool, cut a V-notch through the entire length of the crack, up to 1/8 to ¼ inches deep. Open the crack slightly and remove loose material. While opening the crack may seem counterintuitive, it is necessary so that the joint compound would stick. Be gentle while scraping off the crack. Then, a shop vacuum removes the crumbs and dust from the crack.

2. Prepare the drywall tape

Measure and cut one or more lengths of paper drywall tape so it would fit the crack. Drywall compound quickly dries, so cutting the tape in advance prevents accidentally making creases, bumps, and folds. Use scissors or a utility knife to cut the tape. If the crack is near a door frame or the corner near the ceiling, apply painter’s tape on them to protect their surface from the drywall compound.

3. Apply the drywall joint compound

Mix the drywall joint compound before use, as needed. Scoop up a small portion of it using a 6-inch drywall knife, then smooth a thin layer of joint compound over the crack. Make a path that’s a bit wider than the paper tape. Smooth using long, continuous strokes, and move quickly as joint compound dries fast. Layer on as many coats as needed to fill the cracks, but the average is three coats.

Drying can take from 20 minutes for each coat to 24 hours for a thick first coat. If the cut is deeper than ¼ inch, you may need to press a strip of mesh or paper tape into the first layer of joint compound before it dries to better seal the crack.

4. Apply drywall tape to the crack

Lay the tape unto the mud by hand, then smooth it with a 6-inch knife with one or two passes. You need to flatten the tape and ensure full contact with the compound, ensuring there are no air pockets or wrinkles. Also, be careful not to overwork the tape and tear it. Let the mixture dry completely.

5. Put compound over the tape

Using a 6-inch knife, add a layer of joint compound over the taped area, so the compound extends past the edges of the tape. Smoothen out the compound so it’s flush and level with the surrounding surfaces.

6. Sand the repaired area

Lightly sand the compound using a 150-grit sanding sponge or medium-grit sandpaper to smoothen out bumps or ridges. Be careful not to sand so hard that you expose the tape.

Repairing Cracks on Plaster Walls

A plaster wall crack repair

Plaster walls have two layers: the outer plaster and the inner wooden or metal lath. With plaster, the best way to repair is to preserve the existing plaster and fix it instead of tearing it out. A successful repair of plaster cracks requires taking it slow and being patient enough to add multiple layers of drywall joint compound to the wall.

Tools and Materials Needed:

  • 1 ¼” drywall screws
  • Putty knife
  • 6-inch taping knife
  • Ready-mixed or setting-type joint compound
  • Shop vacuum
  • Self-adhesive fiberglass mesh tape
  • Wet sponge
  • Fine sandpaper

Instructions: 

1. Check the crack to see if it gives

Gently press the wall near the cracks, and if the plaster moves toward the wall, it means that the plaster has likely come apart from the lath strips. Lath strips are wooden strips with thin gaps between them. If plaster has come loose, screw them into the lath strips using one ¼” drywall screws. Bury each screw head to the plaster. Be careful and don’t use longer screws as they may puncture an electric cable behind the wall.

2. Widen the crack

Like when repairing drywall, you have to widen the crack so you can create a wider surface for the joint compound to stick to. Use a putty knife while doing so. Use a shop vacuum to clean up debris.

3. Apply joint compound

Spread the ready-mixed or setting-type joint compound over the crack using a putty knife or taping knife. Ready-mixed joint compounds can be applied more smoothly, while a setting-type joint compound must be mixed using a mud tray and a putty knife or taping knife. Smooth it out when partially dry to lessen the need for sanding.

If the crack is huge, cover it with self-adhesive fiberglass mesh tape before applying the joint compound. This would help prevent the new plaster from cracking if a movement on the wall caused the first crack. Let it dry completely.

4. Apply layers of compound over the taped area

Apply two to three layers of compound over the taped area. Smooth out the final layer using a wet sponge. Using a taping knife, extend the compound to another two to three inches outside the edges of the previous layer. The last layer must extend up to 12 inches beyond the original area.

5. Sand the repaired section

Using fine sandpaper, lightly sand each layer to remove bumps and keep it level with the rest of the wall. If you see a raised section, sand it flushes to the wall before painting. Wait at least 24 hours before painting to make sure the plaster is completely dry.

Fixing a Concrete Wall Crack

Concrete walls are usually load-bearing walls. If there are minor cracks, you can quickly patch them up, but if they are major fissures, it can be a sign of poor structural integrity. Here’s how you can fix a concrete wall crack.

Tools and Materials Needed:

  • Chisel
  • Hammer
  • Paint brushes
  • Concrete bonding adhesive
  • Patching mix
  • Stiff putty knife or pointed trowel
  • Shop vacuum
  • Hair dryer

Instructions: 

1. Enlarge the crack

The patching material for concrete is heavy, and it cannot infiltrate a thin crack. To start, chip away more concrete up to 1 inch below the edges of the crack using a chisel and hammer. This will give you more surface area for the concrete bonding adhesive to grip.

2. Clean debris

Remove debris from the cracks using a paintbrush or a shop vacuum. Rinse the area with water and dry it using a hair dryer.

3. Prime the area

Using concrete bonding adhesive, prime the areas with cracks. This will help the patching material stick better to the concrete. Using an old paintbrush, spread a thin layer around the edges and deep into the cracks.

4. Apply more coats of concrete patching

Using a stiff putty knife or pointed trowel, apply multiple coats of concrete patching. Make sure to press each layer to the crack and let it completely dry in between coats. Repeat until it’s filled and level with the rest of the wall.

5. Add texture

Unlike drywall or plaster, concrete doesn’t need sanding. In fact, the patched area will look out of place if it’s smoother than the rest of the concrete wall. Add texture by applying a coat of patching mix to a piece of wood, then rough it up the wall to see if the texture matches.