How to Fix Large Cracks in Ceilings

Although plaster ceilings are long lasting, they are susceptible to temperature fluctuations, water damage and settlement, all of which may crack the plaster. Plaster ceilings are applied to wood lath systems, which may expand in humid weather and contract in dry weather. Continuous expansion and contraction typically causes plaster ceilings to crack and possibly loosen them from lath systems. While cracks in durable plaster are repairable, plaster ceilings already loosened from lath systems are too severely damaged for repair and may collapse. Fixing large cracks in a structurally sound ceiling restores its appearance.

Drop cloths
Stepladder
Safety glasses
Drywall screws
Plaster washers
Cordless drill
Joint compound
Smooth trowel
Screen door replacement wire
100-grit sandpaper
Tack cloth
Ceiling primer
Roller brush
Ceiling topcoat paint

Instructions

- 1
  Remove all furniture from the room. Cover the floor under the cracked portion of the ceiling with drop cloths.
- 2
  Access the cracked ceiling from a stepladder. Wear safety glasses during ceiling repairs protecting your eyes.
- 3
  Fit a drywall screw through a plaster washer. Screw the drywall screw thorough the cracked plaster and into the wood lath using a cordless drill. If you miss the lath when screwing in the drywall screw, simply remove the screw and try again until you find the lath.
- 4
  Continue fitting drywall screws through plaster washers and driving the screws into the plaster along the crack. Evenly space the washers about 1 inch apart on the ceiling.
- 5
  Spread a one-eighth inch thick bed of joint compound smoothly over the crack using a smooth trowel. Fully cover the plaster washers and don’t let the compound dry.
- 6
  Press screen door replacement wire into the fresh joint compound bed. Skimming the trowel along the screen wire implants the screen in the wet compound.
- 7
  Let the patched ceiling air dry for 24 hours.
- 8
  Rubbing 100-grit sandpaper over the joint compound’s raised areas smoothens the patched area.
- 9
  Skim joint compound over any sunken patches in the repaired area if necessary making the area level. Apply the compound as before. Let the joint compound set for 24 hours.
- 10
  Sand the entire patched area with 100-grit sandpaper until the ceiling is completely smooth. Wipe sandpaper dust off the ceiling using a tack cloth.
- 11
  Apply an even coat of ceiling primer over the patched area using a roller brush. Let the primer fully air dry.
- 12
  Coat the primed area with two separate, even ceiling topcoat paint coats using a roller brush. Make sure the roller brush is clean. Let each separate coat thoroughly air-dry.

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