Plaster Repair

Millions of older homes and retro homes have plaster walls, the precursor to drywall. This Fix-It Guide on plaster repair tells how plaster works, what often goes wrong, how to identify a plaster problem, and what parts and tools you will need to fix it. It then gives instructions for how to repair a small or large crack in plaster and how to repair a small hole or bulge in plaster. After your plaster repair, you will likely need paint repair.

How Does Plaster Work?

Plaster is a pasty composition of lime, water, and sand that hardens when it dries. It’s used for coating walls, ceilings, and partitions. Plaster is spread over masonry or lath (strips of wood, metal, or gypsum). In older homes, plaster was applied in one to three coats. All-purpose, one-coat plasters are now available to make plastering easier. The numerous plaster-patch products available make repair easy, too.

What Can Go Wrong with Plaster?

Plaster walls and ceilings can develop small to large cracks from drying or ground movement. Furniture, doorknobs, and other objects also can make holes in plaster. If it becomes wet, plaster can bulge or even disintegrate.

Fix-It Tip

Which plaster? You can patch a hole in plaster or drywall with joint compound, spackling compound, or patching plaster. Each has advantages and disadvantages. Joint compound applies smoothly and sands easily, but takes 24 hours to dry and it shrinks. Spackling compound dries quickly and shrinks minimally, but is harder to sand smooth. Patching plaster dries in as little as two hours, doesn’t shrink, and is durable, but it is difficult to sand.

How Can I Identify a Plaster Problem?

• If a plaster wall or ceiling develops a crack, you can fill it in (see below).
• If a plaster surface suffers a hole or bulge, you can also fill it (see below).
• If there is a larger hole in a plaster ceiling, you can most easily repair it with a ceiling patch kit.

Fix-It Tip

Patching plaster powder, when mixed with water, must be used quickly before it dries. If it begins to get too hard to use, add a little water to thin it out. If in doubt, throw it out.

What Do I Need for Plaster Repair?

Plaster patching materials and tools are relatively easy to find at larger hardware stores and home centers. Here’s what you’ll need to patch plaster:

• Patching plaster
• Sandpaper
• Primer and paint
• Broadknife or putty knife
• Mister
• Latex bonder
• Small soft-bristle brush
• Masonry chisel
• Hammer
• Vacuum cleaner

What Are the Steps to Plaster Repair?

Repair a small crack in plaster:

1. Widen the crack to about 1/8 inch using a chisel or pointed tool, then remove any loose plaster.
2. Fill the crack with patching plaster following directions on the container.
3. Once the plaster is dry, sand with progressively finer sandpaper.
4. Prime and paint (see Paint Repair).

Patch a large crack in plaster:

1. Widen the surface of the crack using a hammer and chisel.
2. Remove debris with a small, soft-bristle brush.
3. Thoroughly wet the crack so it will absorb the plaster patch.
4. Use a putty knife or broadknife to spread patching plaster (prepared according to package directions) in the hole.
5. Allow to dry for 24 hours or as directed by the patch manufacturer.
6. Apply a second coat of patching plaster and allow it to dry before continuing.
7. Sand the surface smooth, seal it with primer, then paint (see Paint Repair).

Repair a small hole or bulge in plaster:

1. Identify the cause of the hole. If the problem was behind the wall or ceiling (such as a pipe), first repair the underlying problem. If you can’t determine the cause of the damage, consider hiring an experienced remodeler. Make sure you solve the problem, not just plaster over it.
2. Use a masonry chisel to dig back until you hit solid plaster. Vacuum or brush out debris.
3. Dampen the edges of the hole for better adhesion.
4. Apply patching plaster mixed according to package directions, starting from the edges of the hole and working toward the center.
5. Use a broadknife to smooth the surface of the patch, then let dry for 24 hours or as recommended by the plaster manufacturer.
6. Sand the surface, prime and paint (see Paint Repair).

Fix-It Tip

Instead of a second coat of plaster patch, apply a top coat of joint compound. It’s easier to sand and finish.