How to Repair Plaster Ceilings With Setting Compounds

Assess the extent of the damage. A hairline crack or chip may be the first sign of a more significant problem.

Use a crack widener or a triangular can opener to gently open up the crack. Work slowly and carefully to avoid taking down large chunks of the ceiling.

Apply a thin coat of setting compound, such as joint compound, with a trowel. Use smooth, steady movements to minimize damage to the surrounding plaster.

Cut a piece of fiberglass mesh tape long enough to bridge the crack then press it into the wet setting compound. Ensure that the tape adheres well but avoid overworking the setting compound. Allow the setting compound to dry, according to the manufacturer’s instructions.

Use the trowel to skim-coat a second layer of setting compound over the tape. Apply the setting compound as evenly as possible and feather the edges to blend with the existing plaster. Allow the setting compound to dry.

Apply a very light, even third coat of setting compound with the trowel. Even out the surface as much as possible and allow the compound to dry completely.

Use a block sander and fine-grit sandpaper to lightly sand the repair smooth.

Remove the sanding dust and plaster debris with a damp sponge. Thoroughly wring out the sponge and rub lightly to avoid re-wetting the joint compound.

Dry the repaired area carefully with a soft, micro-fiber towel.