How to Fix Large Holes in Plaster Walls

Sanding and smoothing remove edges around the plaster patch.

The methods and materials used to repair plaster walls depend on the size of the holes. Small holes are 1/2 to 1 1/2 inches in diameter, medium holes are 1 1/2 to 6 inches in diameter and large holes are over 6 inches in diameter. Metal mesh patches and patching plaster are sufficient to repair small and medium holes. But large holes in plaster walls require preparing and affixing a plaster patch large enough to cover the entire span of the hole.

Things You'll Need

• Pencil
• Knife or small keyhole saw
• Plaster board scrap
• Patching plaster
• Putty knife
• Sandpaper
• Paint
• Mask
• Eye protection
• Gloves

Instructions

1. Draw a neat and even square on the wall around the hole with a pencil, and cut the square out of the wall as neatly as possible using a small saw or knife. Handle the cutout carefully so it doesn't break.

2. Trace the cutout piece of wall on a piece of plaster board, and trace a 2-inch-wide frame around the traced square to mark the location for cutting.

3. Cut the traced piece from the plaster board, and remove the paper affixed to one side of the board.

4. Remove the plaster from the frame area that was traced around the plaster patch. You will have a plaster patch that has a 2-inch paper frame.

5. Apply patching plaster around the edges of the hole in the wall and around the edges of the plaster patch. Use a putty knife to apply and smooth the plaster.

6. Place the patch over the hole in the wall, and press the paper frame in the plaster. Hold the plaster patch in place until the patching plaster sets.

7. Sand the edges of the plaster patch lightly with sandpaper, and paint the patch to match the wall color.

Tips & Warnings

• Have on hand paper tape, putty and a bucket filled with water to help with the job.

• Plaster products usually dry quickly, which requires working quickly to apply and smooth the plaster.

• An alternative method for repairing a large hole in a plaster wall involves using screws to attach two 1-by-3-inch pieces of wood inside the cutout cavity at the left and right edges, with a small part of the wood pieces overlapping into the hole. Attach the plaster patch with construction adhesive, drywall screws and joint compound around the edges of the plaster patch. Finish up by hiding the joints with paper tape pressed into the compound around the edges of the plaster patch; sanding; two more compound coats; and a final sanding before priming and painting the patch.

• When using patching plaster or compounds, wear a mask, or provide ventilation in the area where you are working. Eye protection and gloves provide protection from dust, flying particles and toxic substances coming into contact with your skin.

References

• This Old House: Hole in the Wall Help
• Michigan State University Extension: Wall Repair and Fasteners
• Home Depot: Patching and Repair

Resources

• National Park Service: 21 Preservation Briefs