How to Paint Over Old Plaster

Remove flaking plaster by hand or chip it off with a chisel or putty knife. If portions of the plaster are on the verge of falling off, it's best to remove them and patch the area.

Use 150-grit sandpaper to smooth out any rough edges around cracks, holes or freshly chipped-off plaster.

Vacuum up any plaster dust around the workspace using a shop vac or a regular vacuum hose attachment. You don't want to wipe up plaster dust using water, as this can damage exposed plaster surfaces.

Apply patching plaster to any holes or cracks using a putty knife. Patching plaster is malleable and gooey, much like thick mud, and it spreads easily.

Smooth the wet patching plaster using a putty knife. Wait for the new plaster to dry.

Sand the new plaster patches with 200-grit sandpaper until it is flush with the existing plaster wall surface. Now that you have evened out the old plaster surface, it's ready to accept paint.

Tape any trim with painter's tape. This protects it from stray brush strokes.

Paint the edges of the plaster surface with a paintbrush, and paint main surfaces using a medium-nap paint roller. Plaster surfaces accept new paint even without primer, but you may require two coats if you're going from a dark color to a light color or vice versa. Regular latex paint works well on most old plaster. However, some old plaster walls are really rough and unstable, even after extensive patch-work. If your plaster wall is very callous, use an elastomeric latex paint. Elastomeric paints provide less coverage per gallon, but these thick paints offer smooth coverage even over a rough plaster surface.

Peel off any painter's tape after the paint has dried.