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How to Patch a Plaster and Lathe Ceiling

Ask This Old House general contractor Tom Silva helps a homeowner repair a cracked plaster ceiling in an older home

Steps for patching a plaster and lathe ceiling:

  1. When originally installed, wood lathe was nailed to the ceiling joists. Plaster mixed with horsehair or goat hair was then forced onto the lathe, forming a key that holds it to the lathe.
  2. One option is to cut out the damaged area and install a 3⁄8” thick sheet of blue board and plaster.
  3. Cover the work area with drop cloths and work off of a rolling scaffolding platform, which can be rented or purchased.
  4. Use a drill/driver to secure a piece of 1x3 strapping to the structure above the ceiling. Repeat this process several times in the area of the cracks.
  5. For areas where there is no structure above, attach a piece of strapping perpendicular to the others and insert filler pieces of strapping in the gaps between the strapping. Slowly tighten the perpendicular piece.
  6. Use a drywall screw with a plaster washer to re-secure the damaged sections of plaster to the lathe.
  7. Remove the strapping.
  8. For areas where the washers don’t hold or the plaster is very damaged, cut out the plaster and create a patch using drywall. Secure the patch with 1 5⁄8” drywall screws.
  9. Scrape away any loose veneer.
  10. Mix a batch of plaster and joint compound to ensure good adhesion.
  11. Place the plaster mix on a hawk and trowel it over the damaged areas.
  12. To keep the plaster from cracking and to hide the screws, set a fiberglass screen into the first coat of plaster.
  13. After the first coat sets, apply a second coat, filling any voids.
  14. Use a felt pad to finish the job and smooth out the ceiling.

Resources:

The ceiling washers, drywall board, plaster, joint compound, fiberglass window screen, trowel, 13x13-inch magnesium hawk, and felt pad brush can be found at home centers and hardware stores.


Tools: