Drywall 101

Why do Drywall Seams Crack?

You have just moved into your new house or reoccupied the rooms that you had renovated. The new drywall was painted and looked beautiful for the first six months and then after the winter thaw you start to see seams cracking and screws popping through the paint. Our first inclination is to blame the drywaller. We can't let him off the hook too quickly because it may very well be his fault. However, before we blame him for the problem, it may be good to understand some of the reasons drywall seams crack or screws pop.

Drywall tape can be likened to a 'band-aid' for the fault line. Where two sheets of drywall meet, the seam is the weakest point in the wall. Drywall tapers spread mud and tape on the joint to give strength to this area and then add layers of drywall mud to feather the seam smooth to the rest of the wall. When a house settles or walls move, drywall seams may crack if there is a "weak link". One reason for cracking is because the wrong type of drywall mud was used to the tape to the drywall seams. Some drywall mud has more adhering ability and is intended to be used in the drywall taping step whereas other types of mud should only be used in finishing. Other drywall mud products are intended only for second or third coats. Some drywall tapers say that mesh tape should never be used in drywall taping because it is not as strong as paper tape. Other drywall tapers say that mesh tape is sufficient as long as it is used with quick setting drywall mud (SHEETROCK® BRAND easy-sand or Pro Form® BRAND stay-smooth joint compounds.)

Drywall corner bead will at times crack as well. One reason is that when the corner bead was installed, it may not have been installed to maximize strength. There are different types of corner beads and various installations. If screws or nails were used there may have been too few. If vinyl bead was used with spray adhesive, perhaps not enough glue was used. Different drywall Tapers and drywall Hangers have different opinions as to what is the strongest process. Many however feel that the "tape on" corner bead is the strongest and least prone to cracking. See also how to coat corner bead?

Another common problem with drywall is nails popping, where you can see what looks like the head of a nail in the paint. This usually occurs within the first year after a drywall job has been completed. Drywall screws or nails are used to secure the drywall to the studs below. The head of the screw/nail puts pressure against the paper on the surface of the drywall. If the screw head goes too deep and busts through the paper into the gypsum layer below, it no longer has holding power. When installing drywall, Drywall Hangers will at times use construction adhesive on the studs below and then use nails or screws to hold the sheet until the glue has time to dry. When this is done it reduces the number of nail pops. However, this is not a fix-all.

This being said, drywall tape's strength is limited. Construction adhesive helps to hold the sheet in place but fasteners, drywall tape and corner bead all have limited strength. If a house settles and walls move to any great degree, no amount of tape or glue will keep it from cracking. When cracks develop in a house usually they run along high stress areas. High stress areas include areas above doorways and windows and over beams that span long distances. If any part of the house was built on fill-dirt it will have a greater possibility of settling. Most new houses will settle some within the first year. Good drywall techniques will limit the occurrence of cracks and nail pops.

In summary, cracks that run along high stress areas of door and window headers or ceilings with long open spans may be a result of the building settling. There is probably nothing the drywall finisher could have done to prevent it. Extensive cracking especially in areas that are not high stress points may indicate that there was some delinquency on the part of the Drywall Hangers or Tapers. Most reputable Drywall companies will be willing to repair minor cracking or nail pops within one year of the finish of a project. Don't be too quick to blame him when he comes. It may not be his fault.

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