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Mauro Henrique gives Kevin O’Connor a lesson on patching cracks in plaster and drywall. After explaining to Kevin that his paint job is only as good as the prep work, the two discuss where cracks are most likely to occur before diving into a few repairs.
Time: 4 hours
Cost: Under $30
Fiberglass mesh drywall tape [https://bit.ly/3q8EjB7]
Joint compound [https://amzn.to/3zMZ88t]
Flexible patching compound [https://amzn.to/3Ge6Evn]
Tack cloth [https://amzn.to/3Gijqck]
Utility knife [https://amzn.to/3GlduPY]
Putty knife [https://amzn.to/3FkCqWp]
Steps for repairing plaster walls
1. Start the project by cleaning up the crack with the utility knife. Look for compound, paint flakes, and other debris in the crack and scrape it out.
2. Using the putty knife, apply a thin coat of joint compound to the crack. Start at the top of the crack and drag the compound down, pushing it into the crack as you go. Remove the excess compound by pulling the blade of the knife across the crack at an angle (not perpendicular to the crack).
3. Apply mesh tape over the fresh compound. Starting at the top, lightly press the mesh tape into the bed of compound before using the putty knife to cut it at the bottom.
4. Immediately apply a second coat of compound over the top of the mesh tape. Starting at the top of the tape, apply the compound and remove the excess. Wait 45 minutes to an hour so it can dry.
5. Lightly sand the repair area to remove any high spots and ridges while also feathering the edges of the repair. Use the tack cloth to remove the dust. If the repair or crack is still visible, apply a third coat and feather the edges with sandpaper once dry.
Patching Cracked Plaster: Small cracks
You can handle some small cracks with a two-coat process using a flexible patching compound, and there isn’t any sanding required.
1. Ensure that the crack is free of debris by scraping the putty knife over the crack.
2. Apply the flexible patching compound to the crack. Start at the top and work your way down, pushing the compound into the crack.
3. It’s important to remove the excess patching compound as it’s not sandable. Drag the blade of the putty knife across the crack at an angle (again, not perpendicular). Ensure that there aren’t any high spots or mounds left behind before allowing the compound to dry for at least two hours.
4. Once dry, apply a second coat of the flexible patching compound in the same manner as the first coat. Again, be sure that there aren’t any high spots or ridges left behind. Allow this coat to dry before painting.
Where to find it?
Mauro shares the best techniques for patching and repairing cracks in plaster walls. His go-to material is a flexible patch compound, Sheetrock® Brand [https://www.usg.com/content/usgcom/en.html/] Dust Control Patch and Repair Compound [https://amzn.to/3Ge6Evn], specifically used for stress cracks on the wall. Mauro also used fiberglass drywall tape 2”x 150’ (50mm x 45.72m) by Dynamic [https://bit.ly/3q8EjB7]
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From the makers of This Old House, America’s first and most trusted home improvement show, Ask This Old House answers the steady stream of home improvement questions asked by viewers across the United States. Covering topics from landscaping to electrical to HVAC and plumbing to painting and more. Ask This Old House features the experts from This Old House, including general contractor Tom Silva, plumbing and heating expert Richard Trethewey, landscape contractor Jenn Nawada, master carpenter Norm Abram, and host Kevin O’Connor. Ask This Old House helps you protect and preserve your greatest investment—your home.
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How to Repair Cracks in Plaster Walls | Ask This Old House