How to Fix Cracks in Walls in Older Homes

Cover the flooring below the cracked plaster wall with a drop cloth. Put on eyewear and durable work gloves for protection.

Slide a utility knife along the crack to widen the space to 1/8 inch. Disregard this step if the crack is already 1/8 inch wide or more.

Fill an all-purpose bucket with 1 gallon of warm water. Stir 1 tablespoon of trisodium phosphate into the water.

Scrub the solution onto the cracked plaster using a soft scrub brush. Thoroughly clean all plaster dust and grime from the crack before patching the wall.

Refill the bucket with water. Saturate a sponge in the fresh water and then wipe the crack and surrounding plaster to rinse off the solution.

Dry the cracked plaster thoroughly with a towel.

Stick self-adhesive fiberglass mess joint tape over the cracked plaster. Fully cover the entire crack with the joint tape.

Rinse the sponge thoroughly and then wring it out. Wipe the taped crack with the moist sponge.

Use a wide-blade putty knife to apply a 1/8-inch-thick coat of pre-mixed joint compound smoothly over the moistened joint tape . Let the wet compound dry for 24 hours.

Spread another 1/8-inch-thick coat of the joint compound evenly over the previous coat using the putty knife. Feather the edges of the joint compound slightly to overlap about 1 inch onto the undamaged plaster on both sides of the crack. Let the wet compound dry for 24 hours.

Sand the dried joint compound lightly with fine-grit sandpaper. Smooth the joint compound until the patched area blends with the surrounding wall.

Coat the sanded joint compound with latex primer using a paintbrush. Let the primer coat dry for 24 hours.

Brush latex paint over the primed area using a clean paintbrush. Use paint that matches the wall. Let the paint dry for 24 hours.