How to Fix a Crack in Plaster Walls Using Plaster

Clean the crack by cutting away loose plaster with a utility knife and smoothing the crack's rough edges. Because plaster creates a stronger bond with a crack that is wider near the bottom, widen the crack if necessary.

Mix plaster patching compound with water in a small bowl, following the manufacturer's instructions on the compound's label. Most plaster compounds require mixing them with just enough water to form a paste the consistency of firm butter.

Fill the crack with the plaster patching compound using a putty knife. Smooth the surface with the putty knife.

Place either a piece of perforated patching tape or a wall patch over the crack. Use a wall patch instead of tape for large cracks and holes. Whether you use the tape or patch, use a piece wide enough to extend beyond the sides of the crack. Press the tape or patch into the plaster in the crack.

Draw the blade of the putty knife over the top of the tape or patch, pressing lightly but firmly to expel excess plaster through the perforations. Smooth the plaster over the repaired area, feathering the edges into the surrounding undamaged wall.

Sand the patched area lightly with fine-grit sandpaper after the plaster dries completely. Sand until the patched area is smooth and blends into the surrounding wall.