Before patching, figure out what the wall is made of
Drywall comes in panels with taped seams. Traditional plaster is built in coats over wood or metal lath, although there are several later plaster systems too. A crack along a drywall seam is not repaired the same way as plaster that has pulled loose behind the finish. Also pay attention to movement: a stable hairline crack is different from a widening diagonal crack or a bulging section.
Drywall holes need support; failed seams need new tape
A dent may only need compound. A hole needs backing or a secure patch so it cannot flex. Loose tape and recurring seam cracks should be opened and retaped, not buried under another thin skim. Each coat gets wider so the edge fades into the wall instead of leaving a hump.
Loose plaster has to be secured before the crack is filled
Plaster can feel hard at the face while separating from the lath. If the area moves when pressed or sounds hollow across a broad section, filler alone will not hold it together. Stable cracks can often be reinforced and patched. Loose or bulging areas may need to be reattached or selectively removed first.
The patch can be solid and still look obvious
Smooth walls show every ridge, scratch, and pinhole. Textured walls can leave a flat island in the middle of the pattern. Window light and ceiling fixtures make both problems easier to see. A final check after primer catches flaws that disappear under sanding dust but show up again under finish paint.
- Repair the cause of movement or moisture first
- Use a patch method that matches drywall or plaster construction
- Feather the repair beyond the damaged edge
- Prime porous compound and exposed material
- Repaint the full wall when a spot repair would flash
Frequently asked questions
Can joint compound be used on plaster?+
It can be part of some surface repairs, but loose plaster must be stabilized and the repair materials must be compatible with the existing wall. Filling an unstable crack alone does not solve the cause.
Why does a repaired patch show after painting?+
The patch may have a different texture, porosity, or sheen from the surrounding wall. Wider feathering, careful sanding, primer, and repainting the full wall improve the blend.
Should cracked plaster be removed and replaced with drywall?+
Not automatically. Stable plaster can often be repaired. Replacement becomes more reasonable when large areas are loose, badly damaged, repeatedly wet, or impractical to stabilize.