Hyde Job Guides

How to Repair Cracks in Old Plaster Walls

A stable crack in sound, bonded plaster can be filled, taped if needed, and feathered flat. Check for movement, hollow plaster and moisture first, because filling does not cure those.

What you need

• Model 01840Black & Silver® Flexible SS Joint Knife, 6” $29.84 each$20.29 each at 100 or more

  Add
• Model 09213Lightweight Blue Steel Taping Knife, 10” $10.20 each$6.94 each at 100 or more

  Add

• fill and finish compound suited to your plaster
• paper tape or mesh only if the repair system calls for it
• primer approved for the repair
• stiff scraper to open and clean the crack

Steps

1. Press the plaster on both sides of the crack and tap it. Stop if it moves, clicks or sounds hollow.
2. Photograph the crack in raking light and mark its ends in pencil so you can check it later.
3. Open the crack with a stiff scraper, not the knives. Remove loose filler, paint edges and crumbs until the edges are firm.
4. Brush or vacuum out the dust. Apply a bonder only if your repair system calls for it.
5. Press fill into the crack with the 01840 so it contacts both firm edges. Strike it back to the plane the system needs.
6. Let the fill reach the state the product directs. Bed tape or mesh in the named compound if the system calls for it.
7. Cover the repair, then blend a thin wide pass with the 09213 onto sound wall on both sides. Release pressure as the blade moves off.
8. Press and check in raking light, match the wall texture, then prime the whole worked area.

Tips

• Do not widen a stable hairline by habit. Open it only if the repair system needs it.
• Use one repair system from one maker. Do not mix a bonder, fill, tape and primer from unrelated packages.
• Clean the 09213 between passes. One cured crumb under a 10" edge scores the whole feather.
• Dry the blue-steel 09213 blade after use. The 01840 is stainless and tolerates wet cleanup.

Watch out

Questions about the right tool for your job? Email cs@hydestore.com or call 508-916-6442.