Houses built before 1940 have lath and plaster walls. Builders nailed thin, closely spaced strips of wood (lath) to wall studs and then covered them with multiple coatings of a dry powder mixed with water to form a stiff workable paste (plaster). This feature is part of the historical charm of an older home. Like any surface, plaster walls can get dinged, gouged and cracked. Above and beside doorways and windows, are classic areas of cracking. If you plan on repainting your plaster walls, these cracks need to be repaired. The following are instructions for repairing plaster walls with a plaster conditioner, adhesive and a joint compound.


  • Using a 3/16-inch masonry bit (available at hardware stores), drill a hole in the plaster about 2 inches from the crack. 
  • Stop when you hit lath. 
  • Drill another hole about 3 inches from the first and about 2 inches from the crack. 
  • Continue until there is a series of holes about 4 inches apart on both sides of the crack.
  • Vacuum the plaster debris out of all the holes.

Prime and seal:

  • Use safety goggles and disposable gloves. 
  • Spray-pump a stream (one or two squeezes) of plaster conditioner into each of the holes. 
  • Spray the edges of the crack. 
  • Clean up drips with a wet sponge. 
  • Wait 10 minutes for the conditioner to soak into the plaster and wood.

Inject adhesive:

  • Place the adhesive tube’s nozzle in one of the holes. 
  • Squeeze the caulking gun trigger until the glue fills the hole and some comes out around the nozzle.
  • Scrape off any excess and wipe the wall clean with a wet sponge.

Clamp the wall:

  • Place a 2-inch plastic washer over a 1 5/8-inch drywall screw. 
  • Drive it through one of the adhesive-filled holes, into the lath. The screw pulls the lath against the plaster’s backside while the washer gives the screwhead a wide clamping surface.
  • Put washers about 8 to 12 inches apart on both sides of the crack.


  • Wipe excess adhesive with a wet sponge.
  • Wait a day or two for it to cure. 
  • Back out the screws and scrape off the washers. 
  • Scrape off any dried adhesive coming out of the holes.


  • Use joint compound to fill the crack and holes. 
  • Smooth the compound with a trowel.
  • Once the compound sets, sand the area lightly 

Prime and paint:

  • Use high-quality paint and primer to finish the wall.


Properly repairing and repainting plaster walls is an involved procedure! Not up to the task? Call your local professional residential painting experts. They’ll have the knowledge, skill and experience to complete repairs and give you a great paint job. 

Need help repairing and painting your plaster walls? Call the Calgary residential painting experts, Cal Res Coatings at (403) 835-4817. We have experience with exterior and interior painting. We’re a residential painting contractor that strives for quality, has an eye for detail and colour, and will not rest until your job is done to your satisfaction. Request a free quote today.


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