How to fix drywall cracks

The short answer

To fix drywall cracks that stay fixed, open the crack slightly, bed reinforcing tape in joint compound, build the surface up in thin coats, sand it smooth, then prime and paint. Filling a crack with caulk or a single dab of compound usually fails, because the wall keeps moving and the crack reopens. Before you start, check whether the crack is a surface issue or a sign of something moving or leaking behind it.

Why drywall cracks

• Joints moving. Where two sheets meet, small movement shows up as a line in the tape or compound.
• Seasonal movement. Framing takes on and loses moisture and shifts a little through the year.
• Settling. New houses settle in the first years. Older ones can settle unevenly.
• Corners and openings. Stress collects at the corners of doors and windows, which is why cracks often start there.
• Poor original finishing. Missing or thin tape, or compound that was applied too thick and dried badly.
• Water. Leaks soften the board and push cracks open. A crack with a stain is a plumbing or roof problem first.

Ceiling cracks have extra causes. The roof framing can move slightly with temperature, and ceiling boards carry their own weight, so poorly fastened sheets sag at the joints.

Check what it means before repairing

Most cracks are cosmetic. A few are not. Look closer when you see any of these:

• A crack that is wide and still growing
• Diagonal cracks running from the corners of doors or windows
• Doors or windows that have started to stick or no longer close properly
• Stains, bubbling paint or a damp smell near the crack
• Cracks that reappear in the same spot after a good repair

If you see these, find the cause first. A repair done on a wall that is still moving or leaking will fail. In an older Brentwood or East Bay home, that can mean a plumbing leak, a roof leak or a foundation movement question. See our guide to repairing or remodeling an older home for how we think about that.

How a lasting repair is done

1. Prepare the crack. Cut along it with a utility knife and pull away loose material so the repair has a clean groove to bond to.
2. Bed the tape. Press a thin layer of joint compound into the crack, lay in paper or mesh tape, and smooth it flat. Tape holds the repair together as the wall moves.
3. Let it dry. Rushing between coats leads to shrinkage and new cracks. Drying time depends on humidity and thickness.
4. Apply thin coats. Build the surface with two or three thin coats, each one wider than the last, feathering the edges out onto the wall.
5. Sand smooth. Use light pressure and check with a raking light. Wipe the dust off before priming.
6. Prime. Bare compound soaks up paint differently from the wall. Primer evens it out so the repair does not show as a dull patch.
7. Paint. Repaint the whole wall, or at least to a corner, so the patch does not stand out.

Corner and ceiling cracks

Inside corners crack where tape was missing or compound was applied thickly. Cut the crack out, retape and finish. Outside corners usually have a metal or plastic bead. If it is dented, the bead and the compound over it need replacing. Ceiling cracks along a seam follow the same method, with a few extras. Work with a light across the surface to see the repair, and support loose or sagging board with screws into the framing before you tape.

What goes wrong when the repair is rushed

Thick compound cracks as it dries. Missing tape means the crack reopens. Skipping primer leaves a flashing patch in the paint. Sanding hard can cut into the paper face and leave fuzzy spots that show through. Most of these show up days or weeks later, after the paint is on.

Textured walls and ceilings

If the wall or ceiling has a texture, the repair has two parts: fixing the crack and recreating the texture so it blends. That is the step that gives away most do-it-yourself patches. The texture has to match in pattern, depth and direction, and it has to be sprayed or troweled on at the right moment. Practice on a scrap of board first. On a large ceiling with a hard-to-match pattern, repainting the whole surface after the repair hides small differences the way touching up one spot never will.

When to hire it out

A single small crack is a reasonable weekend repair. If you have several cracks, a ceiling to match, a texture to blend, or you suspect water or movement, a drywall professional will save time and get a cleaner result. Our drywall service handles repair, patching and finishing, and our painting service finishes the surface so repairs disappear. Estimates are free.

Drywall cracks: questions