How to Repair Damp Plaster Walls

Plaster was a material used in many older homes before the use of drywall. The wooden parts of the walls were covered in plaster. A plywood sheet covered the wall studs, and plaster was used to cover that. When drywall was invented, plaster was still used to cover the drywall to make a more even finish. When there is a problem with damp plaster, whether from water damage or a leak somewhere, it is necessary to fix it or the whole wall could deteriorate. However, there is no feasible way to fix damp plaster. The best thing to do is remove the old damp plaster and start over with new.

Difficulty: Moderate

Instructions

Things You'll Need:

• Curved metal tool (such as a can opener or bottle opener)
• Utility knife
• Masonry chisel
• Patching plaster
• Finishing plaster
• Hammer
• Sandpaper
• Damp cloth
• Dry cloth
• Putty knife

1. Use a can opener or bottle opener to remove the damp plaster. Undercut the damp area a little so that you have removed some of the dry plaster as well. If there is an issue with a leak or wet wood, replace that before continuing. Any repairs you make to a wet surface will only mess up again.

2. Wipe away any excess plaster with a dry cloth. Dampen the edges of the plaster hole with a damp cloth. Mix up the patching plaster according to the package directions. Fill the hole ½ full with plaster using a putty knife. Pack the plaster in until you can just make a small dent with your thumb. Score the plaster with a knife so that the next layer will stick better. Let dry completely before moving on to the next step.

3. Dampen the first layer of plaster with a damp cloth. Fill the rest of the hole with patching plaster, leaving about a ¼ inch from the original plaster surface. This will leave enough room to match the new plaster to the old plaster pattern. Let this layer dry as well.

4. Fill in the rest of the plaster hole with the finishing plaster using a large putty knife. Level the plaster with the rest of the wall. This will probably require the use of some feathering out towards the old wall. Dip the putty knife in some water and smooth the edges of the finishing plaster again.

5. While the plaster is still wet, use a piece of cardboard or other rough object to match the texture of the original wall. Let the plaster completely dry and then you can paint as desired.

Tips & Warnings

• When leveling the plaster, be sure to keep it level or even a little lower than the original wall height. It is easier to add more plaster than to sand it down to size.
• Wear safety goggles when taking away old plaster or sanding down any edges. Plaster dust can seriously hurt the eyes.

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[aquarijen]

on 5/12/2009 You might need to affix metal lath to the wooden lath below and use plaster primer to the edges since you are likely using a different kind of plaster than they used back in the day (you might be using a pearlite plaster and they were using horsehair, for example). Do the brown coat first and leave it lower than the surrounding area. Then go back to do a finish coat of finish plaster and feather it to the surrounding plaster.