How to Repair Exterior Plaster Ceilings

Many older homes have porches with plaster ceilings, since plaster is strong and versatile. Like interior plaster ceilings, exterior plaster ceilings are prone to cracking. Seasonal changes in humidity cause plaster ceilings and the wood lath boards to which they’re attached to contract and expand at separate rates, producing stress cracks in the plaster. The repetitive movements of plaster and wood laths can eventually generate so many stress cracks that plaster fully loosens from the lath and collapses. While plaster ceilings already separated from lath are irreparable, cracked exterior plaster ceilings still attached to lath are fit for repair and restoration.

Dropcloths
Work gloves
Dust mask
Safety glasses
Drywall screws
Plaster washers
Sturdy metal ladder
Cordless drill
Premixed joint compound
Plasterer’s hawk
Plasterer’s float
Screen door replacement wire
Kitchen sponge
Putty knife
100-grit sandpaper
Tack cloth

Instructions

- 1
  Cover the flooring below the damaged plaster ceiling with dropcloths. Put on work gloves, a dust mask and safety glasses for bodily protection during the repair.
- 2
  Poke a drywall screw through a plaster washer. Stand on a sturdy metal ladder to access the ceiling.
- 3
  Use the drill to screw the drywall screw up through the cracked plaster ceiling and into the wood lath. Serving as an anchor, the plaster washer secures the plaster to the lath. Since wood lath is covered by plaster, it may take several attempts to hit it. In these cases, simply unscrew the screw and move it over an inch until you penetrate the nearest lath. Tightly screw the drywall screw into the lath so the plaster washer presses firmly against the plaster.
- 4
  Continue fitting screws through washers and drilling the screws into the laths along the cracked plaster. Space the screws 3 inches apart so the washers are approximately 1 inch apart on the ceiling. Drill the screws directly over the crack and on both sides of it.
- 5
  Scoop a glob of premixed joint compound onto a plasterer’s hawk, using a plasterer’s float. Use the float to smoothly spread the compound over the cracked plaster. Make the compound layer 1/8-inch thick over the repair and gradually thinner onto the surrounding plaster for feathering purposes. Don’t let the compound bed cure.
- 6
  Press screen door replacement wire into the wet bed of joint compound. Skim the float over the screen until the wire becomes thoroughly embedded in the compound. Allow the joint compound bed to cure for 24 hours.
- 7
  Wet a kitchen sponge with water. Wipe any high areas and ridges of joint compound with the wet sponge until the raised areas are slightly damp.
- 8
  Drag the edge of the putty knife over the damp, softened joint compound to remove excess and level the bed.
- 9
  Apply a 1/16-inch layer of joint compound over the first layer, using the previous application techniques. Feather the edges of the compound as previously and let this coat of compound cure for 24 hours.
- 10
  Sand the cured bed of compound with 100-grit sandpaper until the patched area becomes smooth. Gently rub the loose sandpaper in circular motions over the compound.
- 11
  Wipe the smooth compound bed with a tack cloth to eliminate fine dust and grit particles.

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Ceiling Repairs