Small cracks in plaster are relatively easy to repair, with one condition: The plaster must be firmly anchored to the lath behind it. If, when you push on the wall, it flexes as though it has broken away from its support base, call a plaster specialist—the repair will involve removing the loose plaster and replacing it.
It just takes a little spackling compound to repair fine cracks, nail holes, and gouges in a firmly anchored plaster wall. Here’s how: 1) Wearing safety glasses, take a lever-type can opener and use the point to widen the crack to about 1/8 inch, as shown below. Or, you can use a screwdriver or a utility knife.
2) Blow out the plaster dust and any other debris. Using a medium bristle brush, scrub the area with a solution of water and TSP or a nonphosphate detergent.
3) Cut short pieces of self-adhesive fiberglass mesh joint tape and cover the groove with them.
4) Dip a sponge in clean water and dampen the area.
5) Mix setting-type joint compound and apply it over the tape and groove using a 3-inch-wide putty knife. Smooth it out evenly and allow to dry.
6) Apply another coat of joint compound with a drywall knife or wide-blade putty knife. Apply it smoothly and “feather” the edges so that they taper into the undamaged area. Allow to dry and then sand lightly to blend the patch into the wall at the edges.
7) Prime with a high-quality latex primer and then paint.
Larger cracks can be fixed in a similar way. Widen the crack with the can opener and dampen the edges of the crack with a sponge. Fill the crack half full with patching plaster. When it has dried a little, score the plaster with a nail, as shown at right. This will give the next layer of plaster something to hold onto.
Dampen the patch again and apply another layer of patching plaster to about 1/4 inch of the surface. Let the patch dry and apply a coat of finishing plaster.
