Repairing the Corners of Plaster Walls

Fill the corner crack. Plaster makes for an inefficient filler for large corner cracks. Instead, use a foam crack filler. Shake the can, hold it upside down and spray the foam into the corner crack. Do not overfill because the plaster will expand. Give it a few hours to dry.

Cut off any excess foam. Use a utility knife to pare away any foam that is on the outside of the corner crack. Don't take away too much, just enough to even out the surface of the foam.

Wear protective gear. Plaster of Paris can cause respiratory problems and even burns. Put on safety glasses, a mask and rubber gloves.

Mix the plaster. Follow package instructions and mix the plaster in a bucket.

Begin patching the crack. Load up a small amount of plaster onto a hawk. Use your trowel to scrape a portion of this off and then smooth the plaster over the foam. Work from the bottom up. Do not overapply the plaster -- a thin coat of around 1/4 inch is sufficient. Let the plaster set for 30 minutes.

Sand the plaster, if necessary. Use a hand block sander with a fine grit and smooth out any rough spots on the plaster.

Paint over the patch. Use your wall paint and cover over the area you just patched with at least one coat of paint.