Repair Drywall Cracks at Corners and Seams

Drywall cracks at corners and seams are the most common wall damage you'll encounter, and they're also the most fixable. These cracks happen because the tape that bridges the seams—or the corner bead that reinforces corners—fails, separates, or was never properly embedded in the first place. A settling house, temperature swings, and vibration all work together to crack tape and send joint compound crumbling. The good news is that this is pure muscle-and-patience work. You don't need special skills, and the materials cost almost nothing. The difference between a professional-looking repair and one that shows is attention to feathering—spreading the compound so thin at the edges that the repair disappears into the wall. This guide covers both flat seams and inside corners, since they fail differently and require slightly different technique.

1. Clear the Crumbling. Run your putty knife or scraper along the crack, pushing firmly to find where the tape lifts or separates from the wall. If tape is loose, peel it back carefully—you want to expose any compound underneath that's also loose or cracked. Remove all crumbling compound with your scraper. Don't worry about being gentle here; you're clearing away failed material. For corners, check both the tape itself and the corner bead underneath. If the bead is dented or crushed, that section will need bead replacement (see variations).
2. Smooth the Edges. With a sanding sponge or 120-grit sandpaper, smooth the edges of any remaining compound around the crack. You're not trying to sand the whole wall—just feather the edges of the existing material so your new compound has something to blend into. This also roughens the surface slightly so new compound adheres better. Wipe away all dust with a damp cloth and let it dry.
3. Lock Down Fresh Tape. If you removed tape entirely, you'll need to apply fresh fiberglass mesh tape or paper tape along the seam. Fiberglass mesh is self-adhesive and sticks directly to the drywall; paper tape requires you to embed it in a thin layer of joint compound first. Smooth the tape down firmly so it sits flat with no wrinkles or bubbles. For paper tape, apply a thin coat of compound under it, press the tape in place, then smooth it with a putty knife to remove air pockets.
4. Fill the Void. Mix your joint compound to a yogurt-like consistency—thick enough to hold its shape but spreadable. Using a 6-inch putty knife, apply compound over the entire cracked section, working from the center of the crack outward. Press the compound firmly into the crack to fill any voids, then smooth it level with the wall surface. Don't worry about feathering yet—just fill the crack completely. For corner cracks, apply compound to both sides of the corner, smoothing it into the crease.
5. Vanish into the Wall. Once your compound is roughly smooth, use a wider knife (8-10 inches) to feather the edges. This means dragging the knife lightly along the edges of the compound, extending it further onto the wall with each pass. The goal is to create a very thin, almost invisible edge that blends into the wall. Feather at least 4-6 inches from the center of the crack on each side—wider is better. Work lightly; you're not trying to smooth the whole wall, just the edges of your repair.
6. Wait for Stone-Hard. Joint compound takes 24 hours to dry fully, though it may feel dry to the touch after 8-12 hours. Do not sand or apply a second coat until it's completely cured. Drying time depends on humidity and temperature—warmer and drier conditions speed it up, but don't rush it. You'll know it's ready when it's pure white and rock-hard.
7. Erase the Ridges. Once dry, sand the first coat lightly with 120-grit or 150-grit sandpaper. Focus on smoothing any ridges from your knife strokes and any high spots. Sand in circular motions rather than scrubbing back and forth—this prevents gouging. Check for low spots by running your hand across the repair (dust off first)—you should feel almost no ridge. Wipe away all dust with a damp cloth.
8. Refine, Don't Fill. Apply a second coat of compound over the entire repair, using the same technique as the first coat but with a slightly thinner application. This coat doesn't have to fill anything—it's just smoothing out the scratches and imperfections from the first coat. Feather the edges again, extending them even further out (6-8 inches from center). For corners, make sure the compound is worked fully into the corner crease so there are no shadows or gaps.
9. Patience Pays Off. Allow 24 hours for the second coat to cure completely. Same rules as before—don't rush it, and humidity control helps.
10. Inspect Under Glare. Sand the second coat smooth with 120-grit, then wipe clean and inspect the repair closely in bright light. Run your hand across it and look at it from an angle. If you see ridges, low spots, or shadows, apply a third (finish) coat. If the repair is flat and blends with the wall, you may only need primer and paint. Most seam repairs need a third coat for a truly invisible finish.
11. Skim and Blend. A third coat is typically lighter still—almost a skim coat. Apply it with a wider knife (10-12 inches) and feather it extensively. This coat is about blending, not filling. Some repairs stop at two coats, but corners and seams usually show without that third one.
12. Seal Before Paint. Once the final coat is dry, do a final light sand with 150-grit or 180-grit sandpaper. Sand very gently—you're just deglossing and removing any ridges, not leveling anything. Wipe the area clean with a damp cloth. Prime the repair with drywall primer before painting. Primer seals the porous joint compound so your finish paint color is uniform.