Cracks in ceilings range from minor cosmetic issues to signs of structural problems.
Fixing Hairline Cracks
Apply a thin coat of joint compound over the crack. Smooth flat and allow to dry 24 hours. Sand lightly. Apply a second coat if needed. Prime and repaint.
Fixing Wider Cracks
Apply self-adhesive fiberglass mesh tape over the crack first. Apply joint compound over the tape in thin layers, feathering the edges wide. Sand between coats. Apply two or three thin coats.
Fixing Cracks at the Ceiling-Wall Joint
Remove all old paint and filler from the joint. Apply flexible decorator’s caulk along the joint — not rigid filler. Smooth with a wet finger.
When to Call a Professional
If a crack is wider than 5mm, runs diagonally, or is accompanied by cracks above door frames, have a structural engineer assess the building before attempting repair.