Symptoms
- Fine spiderweb or map-like cracking across the wall
- Longer cracks along corners or ceiling lines
- Plaster feels loose or hollow-sounding when tapped near the crack
Likely causes
- CommonNormal aging of lath and plasterOlder plaster naturally develops fine cracks as the house settles over decades.
- CommonHumidity and temperature swingsPlaster expands and contracts seasonally, which opens hairline cracks.
- PossiblePlaster separating from the lath behind itA hollow sound when tapping near a crack can mean the plaster has pulled away from its wood backing.
What to do
- Tap gently around the crack to check for a hollow, loose sound.
- For fine, stable cracks, widen slightly with a utility knife so filler can grip.
- Fill with a flexible plaster patch compound or fiberglass mesh and joint compound.
- Let dry and sand smooth, feathering into the surrounding wall.
- For loose or bulging plaster, avoid pressing on it and don't attempt DIY repair.
- Prime the patched area before painting to prevent flashing.
- Repaint to match, using a slightly textured roller if the original wall has texture.
Tools and parts
- Utility knife
- Taping knife
- Sandpaper
Plaster patch compoundSearch: “plaster repair patch compound”
When to call a pro
Call a plaster specialist if plaster sounds hollow, sags, or if cracks are widespread, since reattaching or replastering needs specialized skill.
Safety
Use caution
Loose or bulging plaster can fall unexpectedly; avoid pressing on hollow-sounding areas and keep the area clear.