Q. We're getting more nail pops in our drywall applications this year than ever before. I've been told that as wood gains moisture, it swells and squeezes the nail out of the nail hole. Are all these nail pops caused by excessive moisture in the house? How can we prevent them?
A. Corresponding editor Paul Fisette responds: Nail pops are related to changes in the moisture content of your framing, but they're a sign of moisture loss, not moisture gain. Pops generally result when drywall is fastened to the face of framing material with a relatively high moisture content. As the studs dry, they shrink. The point of the fully driven drywall nail stays positioned within the stud at the depth it was originally driven, but the face of the stud or framing member shrinks along the shaft of the nail toward the nail point, leaving the head of the nail proud of the drywall surface.
The shorter the penetration of the nail tip into the wood, the less shrinkage along the shaft of the nail, and the less noticeable the nail pop will be. So one way to minimize the magnitude of pops is to use the shortest nails allowed.
The best advice, however, is to use dry framing lumber. Do not use lumber that is stamped S-green -- that stands for "surfaced-green" and indicates a moisture content greater than 19%. Instead, purchase lumber that is either kiln dried (KD) or S-dry (which indicates a surface moisture content of less than 19%).
You must still verify that the lumber has been kept dry in storage and is as close as possible to the in-service moisture content you want (about 12% to 14%). You can verify that with a moisture meter. Also, it's better to use drywall screws instead of nails.
