Ask Allegra - fixing a growing crack in drywall

Allegra Bennett
Dear Allegra,
I have a crack in my ceiling in the living room and bedroom that has traveled down the wall over time. What can I do to repair that? My house was built in the 1930's. Another thing is the pictures shift on the wall when buses pass by. Do you think that could have something to do with the cracks?
Sharon B.

Dear Sharon,
Consistent vibrations from buses, construction vehicles rumbling by loaded with heavy equipment and materials and just a general heavy traffic pattern in your neighborhood could contribute to cracks in the interior house walls over time. But, typically, cracks in a home's ceilings and walls are the outcomes of how the wallboards are fitting against the joists and studs. These shift over a long time and the resulting fissures are referred to as settlement cracks, which we hear about more frequently in newer homes settling on their foundation. Older homes have the same issues because a house never really fully settles. As it ages new cracks and lines show up whether or not there's heavy traffic flowing by. Yours has been up since the 1930's.

Some breaches look worse than others with a few appearing as an annoying thin hairline, like laugh lines on an experienced face, as it were. Other cracks are more dramatic. Maybe there is a narrow split or a very clear joint separation in the corner of a room, which could be a sign of bigger structural problems and should be looked after by a pro. Each calls for a different repair treatment.

Assuming the cracks in your home are nothing more than a cosmetic repair, how you fill them and make them disappear depends on what the walls are made of. In the 1930's most residential walls were made from plaster and lathe board although there was some experimentation with gypsum or wallboard or sheetrock, as we know the product that is typically used today.

If the wall surface is made of paper, then it is drywall or sheetrock. If the wall is solid, chalky and has no paper surface, it is plaster. Damaged plaster should be repaired with a plaster-based patching material which comes dry and premixed. Drywall repairs do well with joint compound, which also comes premixed.

In either case, after the repair is completed, apply wall primer to the patch areas and paint the entire ceiling and wall. If you just paint the patch area, the patch job will be obvious.

  • Ladder
  • Putty knife
  • Utility knife
  • Thin chisel or flat tipped screwdriver
  • Seam tape
  • Sand paper
  • Sanding block
  • Premixed quick dry plaster paste if the wall is plaster
  • Joint compound for drywall
  • Self-sticking mesh seam tape
  • Primer
Steps for plaster hairline crack repair:
  • Slightly enlarge the crack, using the tip of a screwdriver, or a putty knife to create a ledge the patch material can sit on.
  • Brush away any loose plaster.  
  • Moisten the crack with water using a wet paintbrush or sprayer
  • Use a putty knife to fill the crack with patching material. Overlap the  application on either side of the crack. Smooth away excess with putty knife. Let dry completely — several hours or overnight.
  • Apply another coat and wait to completely dry.
  • Sand the area smooth using a fine grade sandpaper wrapped around a sanding block for ease of use.
  • Prime and paint
  • Brush away any loose debris
  • Apply seam tape over crack
  • Use putty knife and smooth on a coat of joint compound
  • Let first coat dry
  • Apply second coat
  • Sand, prime and paint
Note: Patch material shrinks as it dries. It is important to let the patch area completely dry before sanding and painting. Read the product label and follow the guidelines.
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