Repairing Expansion Cracks in a Wall

Prepare for the work. You will need to wear safety glasses, gloves and a mask. Plaster is a very dusty material that can irritate your lungs and your eyes. If you're working with drywall, it's still dusty and pieces can fly off, causing injury. Lay drop cloths down underneath your work surface.

Remove any debris around the crack. If the wall is drywall, use a utility knife and cut around the crack so that you have a clean work surface. It enlarges the crack, but actually helps it seal better. For plaster, scrape away any debris with a chisel and score the area lightly with the end of your chisel.

Mix the plaster. If you are repairing expansion cracks in a plaster wall, mix together plaster according to the bag's directions. Make only the amount needed or you will end up with a bucket full of set plaster.

Spread the plaster over the crack. Use a trowel and scrape a thin coating of plaster over the crack. Wipe off any excess plaster with the edge of your trowel. Let the plaster set for 45 minutes.

Apply drywall tape over the crack if the fix is for drywall. Use a strip of self-adhesive drywall tape. Lay it over the crack and press the edges down firmly.

Apply joint compound over the tape. Use a putty knife and spread a thin layer of joint compound over the tape. Extend the edges out slightly. Scrape off the excess with the edge of your knife.

Sand down the patched area. This is necessary for either medium. Use a fine grade of sandpaper and go over the area you patched. Work until the surface is smooth to the touch and level.

Prime and paint the patched area. You will now need to match the area with the rest of the wall. Apply a primer first, let it dry and then apply the wall color of your choice.