Interior walls are composed of plaster for durability, fire resistance and sound absorbance. However, plaster walls are not completely resistant to cracks and damages. Shrinking lumber, contracting foundations and fluctuating humidity levels are common causes of cracked plaster walls. Although cracks in plaster walls are normal, they are aesthetically unappealing and detract from a home’s appearance. You need to properly repair cracks to prevent them from quickly reappearing. Fortunately, basic supplies and techniques can effectively repair cracked plaster walls.
Mix powdered joint compound with water in a 5-gallon plastic bucket. Carefully follow the joint compound manufacturer's directions on the product's label.
Sand the dried compound with 80-grit plaster sandpaper. Rub the sandpaper diagonally over the compound until the repair is completely smooth and flush with the surrounding plaster surface.