Drywall Cracks: Which Are Cosmetic, Which Are Warnings, and How to Fix Them

A crack in a wall or ceiling raises an immediate question: is this cosmetic, or is the house moving? Most drywall cracks are the former. Houses expand and contract with humidity and temperature, framing lumber dries and shifts in the first years after construction, and the stress concentrates at the weakest points, usually the corners of openings and taped joints. The way a crack looks tells you a lot about which kind you have.

Read the crack

Crack pattern	Typical cause	Concern level
Thin crack running diagonally from a door or window corner	Normal stress concentration at openings	Low
Straight crack along a taped seam	Tape that lost its bond, or seasonal movement	Low
Crack where wall meets ceiling	Truss uplift or framing movement, often seasonal	Low to moderate
Spiderweb cracks in a small area	Impact or a nail pop beneath	Low
Cracks that reopen every season in the same spot	Ongoing movement	Moderate
Wide crack, uneven on each side, growing, with sticking doors or sloping floors	Foundation or structural movement	High: get it inspected
Crack with water staining	Leak above or behind	Fix the leak first

Before you repair

Mark the ends of the crack lightly with a pencil and the date. Check again in a few weeks. A crack that has grown is still moving, and patching it will not hold. If there is staining, look for the water source: the EPA advises fixing leaks promptly and drying water-damaged materials within 24 to 48 hours to prevent mold.

If your home was built before 1978, the EPA notes it is more likely to have lead-based paint. Sanding and scraping painted walls can create lead dust, so test first or use lead-safe work practices.

Repair a hairline or seam crack

1. Open the crack slightly. Run a utility knife along it to remove loose paint and compound and create a shallow V. This gives new compound something to grip.
2. Clean the area of dust.
3. Apply tape. Spread a thin layer of compound over the crack and press paper tape into it, squeezing out excess with a 6-inch knife. Self-adhesive fiberglass mesh tape can be applied first and covered with compound instead.
4. Let it dry, then apply a second, wider coat with a 10-inch knife, feathering the edges.
5. Finish with a third thin coat if needed, sand lightly, prime and paint.

Filling a crack with compound alone, without tape, usually fails because the same movement reopens it.

Inside corners and ceiling joints

Cracks in inside corners are repaired with paper tape folded along its center crease and embedded in compound on both sides. For recurring cracks where the wall meets the ceiling, a flexible approach often works better than rigid tape: some homeowners cover the joint with crown molding attached only to the ceiling or only to the wall, so the gap can move without showing.

Plaster walls are different

In older homes with plaster over wood lath, cracks often mean the plaster keys that grip the lath have broken and the plaster is pulling away. Press gently beside the crack: if the wall flexes, the plaster needs to be reattached with plaster washers or an adhesive injection system before the crack is taped. Taping over loose plaster only hides the problem until it cracks again.

Prevent new cracks

• Keep indoor humidity steady across the seasons.
• Make sure gutters and grading carry water away from the foundation, as the EPA recommends for moisture control.
• Avoid hanging very heavy items on drywall without anchoring into studs.

Common mistakes

• Caulking or spackling over a moving crack. It reopens.
• Thick single coats of compound that shrink and crack.
• Skipping primer, leaving a dull patch.
• Ignoring a crack that grows or comes with sticking doors.

When to call a pro

Call a structural engineer or foundation specialist if cracks are wider than about an eighth of an inch, are noticeably wider at one end, appear suddenly in several rooms, keep growing after repair, or come with doors and windows that stick, sloping floors, or exterior brick and foundation cracks. Those are signs of movement that a patch cannot fix. A drywall contractor can handle extensive cosmetic cracking, plaster walls and ceilings once the cause is understood.