Drywall seams will crack or separate for different reasons. A damaged foundation can cause it, as well as improper drywall finishing during construction. It could be that the sheetrock hanger didn't use enough screws or nails. If you have a foundation problem you should fix that before spending time on your drywall. A foundation issue is serious; it will cause your windows and doors to bind up and can cause roof problems. When drywall is screwed or nailed to the studs, it makes for a seam every 4 feet...

Hanging drywall, or Sheetrock as it's also called, is easier than plaster if the metal or wood framing is proper. Gypsum board is an economical wall finishing product. The history of drywall begins around 1915. The major component is the mineral gypsum, which is processed into sheets and then wrapped in paper. A variation of the basic drywall is greenboard, which is designed to be more moisture-resistant, and up until recently was the preferred backer for ceramic tile in bathrooms. Today, cement fiber backer board is preferred, and mandated...