How to Repair Exterior Plaster

Chip out the plaster with a chisel and hammer to make smooth edges for the repair job.

Cover over the lath with roofing paper and then with nylon mesh to give the new plaster something with which to adhere. Attach the paper and mesh over the lath with small tacks.

Mix plaster and water in a bucket according to the directions on the package. Use a drill mixer to stir the contents.

Dampen the old plaster around the repair area with a wet sponge to help the new bond with the old.

Scoop out the plaster mix and smear it over the mesh with a trowel. Do not fill in the area up to the surface of the wall. Plaster is best applied in layers. Leave ½ inch of space between the new plaster and the surface.

Wait for the wet shine to dry off the surface and score lines into it to help the next layer bond with it. Cover the surface with plastic and let it to dry for one day.

Mix a second batch of plaster.

Dampen the surface again with a sponge and fill in the area, leaving a 1/8-inch depth between the new surface and the old. Smooth it with a trowel and cover it over again with plastic. Let it dry for three days.

Stir a batch of plaster for the third and final layer. Look at the package and mix it according to the finish coat instructions.

Dampen the surface of the patch area and surrounding surface.

Spread the plaster on the surface to match the surrounding texture. This varies and requires different tools. It might be smooth and applied with a trowel, flicked on to create a bumpy texture or sprayed on for a rough, flat surface.