flexiblefullpage - default
billboard - default

How To Repair a Plaster Ceiling

December 02, 2019

A master stucco and plaster contractor shows how he repairs lath and plaster problems

The Problem: Somebody in the attic stepped onto the plaster ceiling below. A small chunk of plaster is missing, but a large area around it is loose and has separated as much as 6 inches from the lath.

The Solution: Contain the damage and avoid taking down the whole ceiling, then make a durable patch that matches the orange peel finish on the original ceiling.

Here’s an outline of his step-by-step approach:

Define the Size of the Patch

  • Identify “buckles”—creases where loose plaster transitions to tight plaster—then carefully score it with a utility knife.
  • Wear eye protection against plaster dust and debris falling from the attic above.
  • Protect the floor from falling plaster.
  • Be aware that a larger area of plaster may fall than expected.

Remove Loose Plaster

  • Carefully remove pieces of plaster by hand, one piece at a time.
  • Support adjacent pieces of loose plaster to prevent them from being dislodged by the piece being removed. This is especially important at the scored edges.
  • Get a second person involved if necessary.
  • Remove all plaster within the scored area until you reach original plaster at the perimeter that is still tight to the lath.

Clear the Keys

  • Remove plaster from between strips of lath (the keys) using light taps with a hammer or the edge of a trowel.
  • Be careful not to loosen plaster at the edges,

Prep the Lath

  • Wire brush the lath to remove dust and any plaster still clinging to the wood.
  • Brush on a liquid binder, such as Plaster Weld, which removes dust and provides a stronger bond for the plaster.
  • Start at the perimeter, coating the lath and the exposed edges of the existing plaster.
  • Coat all of the wood lath.

Apply Scratch Coat

  • Use quick-set patching plaster (20-minute open time)
  • Start applying plaster at the perimeter first (about a trowel-width)
  • Be sure to push plaster into keys
  • Add a second trowel-width of plaster around the perimeter
  • Fill in the rest of the patch area.
  • You don’t need to “scratch” the scratch coat

Apply the Second Coat

  • When scratch coat is firm, apply second coat.
  • No need to flatten plaster with a darby because patch needs to conform to wavy original ceiling
  • Allow second coat to dry

Flush Up Patch to Existing Ceiling

  • Apply plaster to flush up the patch to the edges of the original ceiling
  • Make sure the patched area flows gently and does is not create a hump in the ceiling
  • Minimize trowel marks
  • Allow plaster to partially dry (+/- 15 minutes) before adding the orange peel finish

Roll the Orange Peel Finish

  • Trowel the perimeter of the patch with a damp foam float
  • Float the rest of the patch to remove any trowel marks (add water to float as needed)
  • While using float, evaluate whether the plaster is ready to be rolled
  • Roll the patched area with a fluffy roller dampened with water

Kirk Giordano is a plaster and stucco contractor in the San Francisco Bay Area. His YouTube channel has a lot more videos.

catfish1 - default