How to Repair Hairline Cracks in Drywall

Even imperceptible shifting of a house foundation may result in small hairline cracks in the drywall. The most common areas for cracks are above the corners of doors, above and below installed windows and in the corners of a room, near the ceiling. When cracks occur, you can repair them by applying drywall mud, letting it dry and then sanding the area before repainting. The use of mesh drywall tape may help the area resist further cracking.

Difficulty: Moderate

Instructions

Things You'll Need:

• Premixed drywall mud
• Drywall mesh tape
• 6-inch taping knife
• 12-inch taping knife
• Hand-held drywall mud tray
• Drywall sander
• Paint

1. Prepare the area by removing nearby wall hangings and by draping the floor with a heavy tarp to prevent damage to the carpet or the flooring.

2. Stir the premixed drywall mud to smooth out any thickened areas, and scoop out a small amount into your drywall tray. A drywall tray is narrow and oblong to hold the mud while providing a smooth edge on which to scrape excess mud from your trowel.

3. Apply a scoop of drywall mud to the hairline crack with the 6-inch taping knife, smoothing the mud into the crack by using pressure as you run the knife from the top of the crack to the bottom. Fill the crack entirely, and use the knife to remove excess drywall mud from the edges of the crack.

4. 
   Mesh drywall tape adds strenght and flexibility.

   Cut a strip of mesh drywall tape approximately 2 inches shorter than the crack, and press it onto the crack while the drywall mud beneath is still damp. Smooth out the tape to eliminate any wrinkles.

5. Scoop up some fresh drywall, mud and apply it evenly over the mesh tape, using gentle pressure to push the mud into the small holes.

6. 
   A wide taping knife smooths out the edges of the mud.

   Switch to the 12-inch taping trowel, and gently smooth the mud along the tape. This wider taping knife pushes the edge of the mud outwards to reduce the appearance of a bulge over the tape. Remove any excess, and allow the wall to dry completely.

7. Repeat the application of drywall mud with the 12-inch trowel, adding a little more to the taped cracks and smoothing them out as flat as possible. Drywall mud shrinks slightly as it dries, so two more very thin coats will add strength without creating a bulge.

8. 
   Drywall sanders quickly smooth the wall.

   Sand the wall with a drywall-sanding pad after the last coat of mud is dry. Use light, even sanding strokes. Run your hand over the repaired seam to check for rough spots. After repainting, any mistakes will become very apparent, so now is the time to make sure the wall is as smooth as you can make it.

Tips & Warnings

• Cover the drywall mud bucket as you work to keep the mud from drying out.
• If you continue to experience cracks in the same place, consult a builder or engineer about stabilizing your foundation or wall structure.

References

• John A. Taylor, Contractor, Taylor Construction, McPherson KS. [phone]

Resources

• Locate hand taping tools online.