My 1920s bungalow has plaster walls throughout. After fifteen years of ownership, I’ve learned more about plaster repair than I ever expected. Here’s what actually works.
Why Plaster Cracks
Houses settle. Doors slam. Temperature changes. Moisture gets in. All of it creates stress that plaster has to absorb, and eventually it cracks. Old plaster also dries out and loses its bond with the lath beneath it.
Hairline cracks are cosmetic. They’re annoying but not urgent. Larger cracks, bulging plaster, or chunks falling off – those need attention before they get worse.
Fixing Small Cracks
For hairline cracks, I widen them slightly with a utility knife – counterintuitive, but it gives the repair material something to grip. Clean out any dust with a dry brush.
Fill with patching compound, pressing it into the crack. Smooth it flat with a putty knife and let it dry. Sand lightly, prime, and paint. Done.
Larger Cracks and Holes
Bigger damage needs more prep. Remove any loose material – if plaster crumbles when you press on it, dig it out. You want solid material around the edges of your patch.
For deep holes, apply patching plaster in layers. Let each layer dry before adding the next. Trying to fill a deep hole in one shot leads to cracking as it dries unevenly.
Finish with a skim coat of joint compound, feathered at the edges to blend with the surrounding wall.
Dealing with Loose Plaster
This is trickier. If a section of plaster has separated from the lath but isn’t crumbling, you can sometimes reattach it.
Drill small holes through the loose area. Inject plaster adhesive through the holes – it expands behind the plaster and glues it back to the lath. Press the plaster against the wall until the adhesive sets. Fill the drill holes afterward.
When to Call It
Massive damage or failing plaster throughout a room might warrant replacing sections with drywall. It’s a judgment call based on how much you value original materials versus your sanity. Some damage is just beyond patching.
