Fixing Cracked Plaster

Important Points to Remember

Many older homes feature lath-and-plaster walls. While plaster is strong and visually appealing, it does come with one downside: it eventually develops cracks.

Latex paint can temporarily conceal hairline cracks in plaster. However, this quick fix may last only a few hours or a few months. Small plaster cracks have a tendency to reappear, so it might be a better idea to enlarge and properly repair them once and for all.

While it may seem counterintuitive, enlarging a small crack often makes it easier to repair than leaving it as is. Use plaster of Paris, which doesn't shrink as it dries, or opt for a pre-mixed plaster repair compound. Follow these steps to fix larger cracks in plaster:

Step 1: Use a utility knife to remove any loose plaster. Angle the knife to create a wider, cleaner opening. Take care to preserve the integrity of the surrounding surface. Clean up the loose plaster and dust with a vacuum cleaner.

Step 2: Mix a thick paste of plaster of Paris and water. Use a paintbrush to thoroughly wet the crack. Fill the wet crack with plaster of Paris (or the repair compound) to its full depth, then smooth the surface with a scraper or trowel. Allow the filled crack to dry for at least 24 hours.

Step 3: Once the plaster has dried, lightly sand the patch using medium or fine-grit sandpaper wrapped around a wood block. If the crack was wide, apply another layer of plaster, re-wetting the area each time. Let the final layer dry for at least 24 hours.

Step 4: Sand the patch lightly once more, then apply a thin layer of paint or primer. Once the primer has dried, paint the entire wall.