How to Repair Historic Plaster

Exterior plaster on older homes is repaired in the same manner as the interior.

Old houses and buildings used a form of wall covering called lathe and plaster. The lathe is 2-inch wide wood strips stretching between the studs. The plaster is a harder version of modern plaster; almost like cement. The plaster on the walls will begin to shift and crack as the building settles. Repairing the plaster in older or historic homes is not as simple as applying more plaster. Small nail holes can be filled with standard plaster. Larger holes or cracks require a few extra steps.

Things You'll Need

• Chisel
• Hammer
• Damp rag
• Patching compound
• 6-inch broad knife
• Nail

Instructions

1. Draw an outline into the plaster for large cracks with a chisel. The outline should be within an inch of the crack on both sides. Press the chisel hard into the plaster to make the line. The purpose is to outline the crack so that you can remove the uneven plaster.

2. Use the chisel and hammer to remove the plaster within the outline from Step 1. Use the hammer and chisel to remove loose plaster from holes, if you are not repairing a crack.

3. Clean the area with a damp rag. Make sure to get any loose particles out of the hole.

4. Use a putty knife to apply patching compound to the hole. Do not worry about filling the hole on the first attempt. You want to cover the hole, but only a little bit at a time.

5. Allow the patching compound to dry. Scratch the surface with a nail to rough up the surface. Wipe clean with a damp rag.

6. Repeat Step 4 and 5 for a second layer. Repeat Step 4 for a third and final layer.

Tips & Warnings

• You may want to experiment with some compound placed on a piece of scrap wood, and different texture tools if your wall is textured. Some older homes used a course sand mixed with the plaster leaving a rough surface. You can do the same to match the texture of the original wall.

• Some older homes used asbestos in the plaster to provide insulation. Be careful when removing the plaster and wear mouth and eye protection.

References

• "Lowes: Complete Home Improvement and Repair"; Don Vandervoort, 2005.