Concrete enforced drywall, also known as cement board, is used in wet areas such as basements or bathrooms. Cement board resists mold because it does not absorb moisture like gypsum drywall, which will mold and crumble when wet. Cement board resists more than gypsum drywall, but it is not impervious to damage. Holes can occur when something hits the drywall in an area where it is not supported by a stud. House settling can also cause drywall to crack.
Things You'll Need
- Flathead screwdriver
- Lightweight surfacing compound
- Fine-grit sandpaper
- Self-sticking fiberglass mesh tape
- Joint compound
- Taping knife
- Carpenters square
- Stud finder
- Utility knife
- 1-by-2 or 1-by-3 scrap wood
- Cement board sheet
- 1¼ inch drywall screws
- 9-inch putty knife
- 12-inch putty knife
Repairing Cracks Shorter than 1 Inch
Widen a narrow crack with a flat head screwdriver by making a V-shaped groove the full length of the crack. Brush off any loose pieces.
Follow the package directions to mix a small amount of lightweight surfacing compound. Smooth the surfacing compound into the crack with your finger. Let the area dry.
Apply a second thin layer of surfacing compound to the crack and let dry.
Sand the area with fine-grit sandpaper until it is flush with the wall. Paint the area with a primer, let dry, then paint if desired.
Repairing Cracks Longer than 1 Inch
Tear a piece of fiberglass mesh tape long enough to cover the entire crack. Stick the fiberglass mesh tape to the crack covering it completely. Press the tape flat.
Apply three coats of joint compound with a taping knife over the fiberglass mesh tape. Let each layer dry before applying the next. Feather the joint compound to blend to the existing wall. Let the joint compound dry.
Sand the area with a fine-grit sandpaper until smooth with the existing wall. Remove any dust from the area with a rag. Paint the area with primer and paint if desired.
Find the studs on both sides of the hole with a stud finder. Draw a rectangle or square around the hole from one stud to the other with a carpenter's square. Cut out the square or rectangle with a utility knife to make an opening. When the blade of the utility knife hits the studs, measure 3/4 inch toward the middle of each stud and mark with a pencil. Cut the drywall away from the middles of the studs. This will give you supports for the new section of drywall.
Cut a piece of 1-by-2 wood for small holes or 1-by-3 wood for larger holes, 2 to 4 inches larger than the width of the opening. Place the wood vertically behind the hole and secure it in place with drywall screws to the drywall above and below the hole.
Measure the opening with a framing square. Use a utility knife to cut out a patch of cement board to the measurements.
Hold the patch into the opening. Screw 1¼ -inch screws through the patch into the studs on either side. Drive the screws as far from the edges of the patch as possible while still driving hitting the studs.
Press self-stick fiberglass mesh tape around the perimeter of the patch, centering the tape on the seam where the existing wall and the patch meet.
Spread joint compound over the patch and mesh fiberglass tape with a 9-inch putty knife and make a smooth surface. Let the joint compound dry overnight then sand the area with fine-grit sandpaper.
Apply a second coat of joint compound and let it dry. Sand with fine-grit sandpaper and then apply a final coat of joint compound with a 12-inch putty knife. Let the final coat dry then sand smooth with fine-grit sandpaper.
Wipe away any dust and apply a primer and paint if desired.
Tips & Warnings
- For a smoother finish, add water to thin out the joint compound in the final layer.
- Avoid oversinking screws into drywall where studs are not present.
- "Do it Herself"; Joanne Liebeler; 2007
- "Home improvement 1-2-3"; The Home Depot; 2003
- Photo Credit drywall tools image by Sherri Camp from Fotolia.com
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