How to Fix Drywall Cracks in Corners (Inside vs. Outside)

Quick answer: An inside-corner crack is usually a failed tape joint; remove only loose tape, bed new creased paper tape in joint compound, and feather two or three finish coats. An outside-corner crack is usually chipped compound or damaged corner bead. If the bead is loose, bent, or rusted, repair or replace that section before refinishing it.

Do not cover a damp, widening, or repeatedly returning crack until you have corrected the leak or movement behind it. The repair method depends on which kind of corner you have.

Inside Corner or Outside Corner? Start Here

What you see	Likely failure	Durable repair
A line in the angle where two walls meet	Loose, split, or poorly embedded joint tape	Remove loose tape and retape the inside corner
Chipped compound on a projecting corner, but the bead is firm and straight	Surface impact damage	Remove loose compound and refinish over the sound bead
A projecting corner that moves, is dented, or shows rust	Loose or damaged corner bead	Replace or refasten the damaged bead section, then refinish
A stained, soft, growing, or repeatedly returning crack	Moisture or ongoing movement	Diagnose the cause before cosmetic repair

Why Drywall Cracks in Corners

Corner cracks usually come from one of four problems: the original tape was not fully bedded, the drywall or framing moved, an outside corner took an impact, or moisture weakened the finish. Seasonal movement can open a small cosmetic line, but a crack that keeps returning tells you the surface is still moving or the reinforcement underneath has failed.

Before cutting anything, check for stains, softness, a loose sheet, a bent bead, and movement when you press lightly near the crack. A widening crack accompanied by sticking doors, sloping floors, or other movement deserves professional diagnosis. A wet corner needs the leak fixed and the material dried or replaced first.

Tools and Materials

• Utility knife and scraper
• 4- to 6-inch taping knife plus an 8- to 12-inch finishing knife
• Joint compound
• Creased paper joint tape for a standard inside corner
• Matching corner bead and tin snips if an outside bead is damaged
• Fine sanding sponge, dust protection, primer, and matching paint

Mesh-tape warning: Do not wet self-adhesive fiberglass mesh. If you choose a fiberglass mesh system, follow its manufacturer instructions; USG specifies a setting-type compound for the first coat over its fiberglass tape. For a typical inside corner, center-creased paper tape is the straightforward system.

How to Repair an Inside-Corner Crack

1. Confirm the corner is dry and stable

Fix an active leak first. If the drywall moves when pressed, correct the loose panel or framing issue before you retape; new compound cannot stabilize a moving joint.

2. Remove only failed material

Score the paint along both edges of the loose tape, then peel or cut away tape that has released. Scrape off loose compound without tearing sound drywall face paper. If the remaining tape is solid and the defect is only a shallow paint crack, a small surface repair may be enough; a split or bubbled tape joint should be retaped.

3. Bed new paper tape

Cut paper tape to length and crease it sharply. Apply an even bed of joint compound to both sides of the corner. Press the tape into the angle and wipe it with a clean knife, removing excess compound while leaving enough behind for a continuous bond. Work carefully so you do not squeeze the joint dry or leave bubbles.

4. Apply thin finish coats

After the bedding coat hardens and dries as the compound manufacturer requires, coat one side of the corner and feather the outside edge. Let it set before coating the other side so the angle stays crisp. Add another thin coat if needed, extending each coat slightly wider than the last.

5. Sand, prime, and paint

Sand only enough to remove ridges; heavy sanding can expose the tape. Remove dust, apply drywall primer over the repair, and repaint. Primer matters because bare compound absorbs paint differently from the surrounding wall.

How to Repair an Outside-Corner Crack

If the corner bead is still firm and straight

Scrape away loose paint and compound. Do not pry on a sound bead. Apply thin coats of joint compound over the damaged area, feathering wider onto both wall faces. Let each coat dry, sand lightly, prime, and paint.

If the corner bead is loose, bent, or rusted

1. Mark a repair section that extends beyond the visible damage and protect nearby surfaces.
2. Cut and remove the damaged bead section without pulling loose the sound bead above and below it.
3. Fit the same profile and material where practical. Attach or embed it using the method specified for that bead.
4. Apply successive compound coats, feathering each coat farther onto the wall.
5. Sand lightly, prime, and paint after the repair is fully dry.

For a full installation overview, see how to install and finish drywall corner bead. USG also publishes a concise paper-faced corner-bead repair method.

Why a Corner Crack Comes Back

• Loose tape was covered, not removed. Compound over a detached tape edge does not restore the bond.
• The joint was squeezed dry. Tape needs a continuous bedding layer underneath it.
• Mesh was paired with the wrong first coat. Use the tape-and-compound system the manufacturer specifies.
• The bead or drywall still moves. Surface mud cannot hold a loose substrate together.
• Moisture remains. A stain or soft board is a diagnosis problem before it is a finishing problem.
• The finish was built too thick. Several thin, feathered coats shrink and sand more predictably than one heavy coat.

Frequently Asked Questions

Can I fill a corner crack with caulk?

Caulk can hide a tiny paint-line gap at some trim transitions, but it is not a substitute for failed drywall tape or a damaged outside corner bead. If tape has released, retape the joint.

Should I use paper tape or mesh in an inside corner?

Creased paper tape is designed for standard inside corners and works with drying- or setting-type joint compounds. Fiberglass mesh products have their own compound requirements; USG specifies setting-type compound for the first coat over its fiberglass tape.

How long should joint compound dry between coats?

Follow the specific product label. Drying time changes with compound type, coat thickness, temperature, humidity, and ventilation. A surface that looks dry can still be soft underneath.

When should I call a professional?

Get help when the crack is growing, repeatedly returning, damp, accompanied by other movement, or caused by a loose or extensively damaged corner system. For other crack locations, use the main drywall crack diagnosis and repair guide.

Sources

• USG Sheetrock Brand Paper Joint Tape
• USG Sheetrock Fiberglass Drywall Tape instructions
• USG Sheetrock Installation and Finishing Guide
• USG Surfaces and Finishes Repair Guides