Repair

• First clean the area and prepare a compound to apply to the crack to seal it. Use a scraper knife or utility knife to free any debris and clean the area. Mix joint compound, for larger cracks, to apply to the crack and fill it. After applying the mixture, take a length of paper drywall tape--long enough to cover the entire crack--and place it over the compound mixture. Using a drywall knife, smooth the tape and remove any excess wet compound. It should take approximately 12 to 24 hours to dry, but you can use a fan to dry it quicker.
  
  Then apply a thin, wider, overlapping second coat of premixed compound. Let dry and, for best results, apply a third coat. Make sure each successive coat fans out wider than the undercoat to ensure a smooth blending with the wall.
  
  

Follow-Up

• Wipe and lightly sand away any excess material from the surface, using a plastic sanding block with a handle and sanding screen or medium-grit sandpaper. Sand so that the edges blend in. If there are any bulging areas or imperfections, sand the wall just until it is smooth to the touch. Be careful not to sand too much or you may need to apply another coat of compound.
  
  

Final Steps

• Ensure the crack is dry and smooth, then paint over the crack with primer. Follow with paint once the primer is dry and covers the crack appropriately. Painting the entire wall may be necessary to match an existing color.