How to Fix Old Cracked Walls in an Old House

By Mark Morris

Homes built in the last half of the 20th century and newer have interior walls made almost exclusively of drywall gypsum board sheeting. This material was an improvement on, and eventually replaced, the traditional lath and plaster interior finishing that had been used for centuries. In old homes, the lath and plaster still exists in many cases and must be treated properly to ensure a good, solid fix that will last.

List of Items Needed

  • Safety glasses
  • Putty knife
  • Rotary tool
  • Metal lath screen
  • Tin snips or power cutting tool
  • Staple gun
  • Vinyl patching plaster
  • Drywall knives
  • Primer
  • Disposable brush
  • Latex paint
  • Paintbrush

    Repair Prep

  1. Remove any and all loose pieces of plaster surrounding the crack. Use a thin putty knife to lightly flick up at the edges any piece that comes away or is loose. Do not pry up pieces that are still adhered to the lath as this base helps make a strong repair.

  2. Scrape the plaster from between the lath boards in areas where the lath is exposed. Use a rotary tool to speed up the process. This will promote a better bond between the repair medium and the lath so that it will not come loose.

  3. Cut a piece of metal lath screen using tin snips or a power cutting tool to fit into any crack or void more than an inch wide in both directions. Fit the lath screen into the crack and staple it to the wood lath boards.

    Application

  1. Apply a coat of vinyl reinforced patching plaster over the lath with a narrow drywall knife. Allow this to set up for about half an hour. Fill any cracks that have developed in its surface with more patching compound and apply a second coat, building on the first.

  2. Continue adding coats, with a 30 minute drying window in between, until you reach the surface of the wall so that the entire repair area is flush with the surrounding wall.

  3. Smooth the plaster off with wide knife, working to mimic the texture of the surrounding wall.

    Finishing

  1. Wait overnight for the patch to dry completely. Fill any cracks that developed with vinyl patching plaster and allow it to dry completely.

  2. Brush on a coat of oil-bonding primer over the repair with a disposable brush and follow the label's recommended drying time.

  3. Apply two coats of latex paint the same color as the surrounding wall to the repair area using a paint brush, feathering the edges out into the original surface to blend the repair in.

Tips and Warnings

  • Wear safety glasses when operating power tools.

© Demand Media 2011