A stable crack in drywall or plaster can be repaired, but the method depends on the wall system. Drywall repairs often involve a joint, tape, and compound, while traditional plaster also requires checking whether the finish remains bonded to its base. A growing crack or building movement needs diagnosis before patching.
Confirm that the crack is cosmetic and stable
Photograph the crack and watch for width changes. New diagonal cracks, separation around doors, bulging, moisture, or repeated movement should not be treated as a simple finish defect.
For drywall, check whether a joint or tape has failed
Remove only loose compound and tape until firm edges remain. An opened drywall joint often needs compatible new tape and several thin coats of joint compound feathered beyond the repair, with proper drying and light sanding between stages.
For plaster, check that the finish is still bonded
If plaster sounds hollow, moves under gentle pressure, or releases in sheets, simply filling the crack will not fix the loose base. A stable crack in firmly bonded plaster can be minimally opened, cleaned, and filled with a product compatible with that wall system.
Finish the surface only after the repair is dry
Level the repair without aggressively sanding drywall paper or sound plaster, remove dust, and prime where the patch or paint system requires it. If the crack quickly returns, stop cosmetic repairs and investigate the source of movement.