Drywall imperfections can include drywall cracking, seam bubbling or wrinkling, corner bead crush or pop, and nail and screw pops through drywall. Usually, these defects are caused by the simple shrinkage of the wood framing members in the house.
In a newly constructed home, we commonly observe nail popping or screws popping through drywall. This is a very common occurrence in new homes after about a year or two. Visually, a popped drywall nail or screw can be identified by what is usually a fairly symmetrical, round protrusion from the face of the drywall wall or ceiling surface, approximately 3/8 to 1/2 inch in diameter. These “pops” normally do not protrude from the plane of the wall or ceiling more than 1/32 of an inch, but that is enough to show up as an unsightly blemish.
The cause of these pops is quite simple: the wood studs and joists delivered to construction sites typically have a fair bit of moisture in them, usually about 19% moisture content (MC). The equilibrium moisture content of these framing materials in a heated home is around 10 %, averaged for the year. The reduction in moisture content causes shrinkage in the wood member: the average “green” two-by-four, with approximately 19% MC, is approximately 1-5/8″ by 3-5/8″ in size, and will shrink to approximately 1-1/2″ by 3-1/2″ at about 10% MC.
Because most houses are erected quite rapidly, and the drywall is applied to the studs before they have had any time to stabilize and dry out, these studs will dry out within the wall space and will actually dry away from the drywall, causing a gap between the back surface of the drywall and the face of the stud. If pressure is applied to the face of the drywall by a person leaning on it or setting a ladder against it, the nail or screw can pop or push its head through the face of the drywall.
The mechanism for ceiling pops can be related to shrinking of the top and bottom wall plates, which forces the drywall on the wall against the drywall on the ceiling,, again causing the gap between the face of the wood framing member (in this case a ceiling joist or truss) and the backside of the drywall to close, forcing the head of the fastener through the face of the ceiling. Truss uplift can also cause movement of the ceiling, causing popping, as well as other problems. Popping caused by either of these mechanisms usually occurs at the perimeter of the room.
Sudden changes in air pressure, most commonly caused when an exterior door or window is quickly opened and/or closed, can cause the drywall on the ceiling and/or the walls to be pressed into or pulled away from their supporting wood framework. This again can cause closure of any gap between the wood member and the drywall, causing the fastener to be popped out of the face of the drywall. Nearby explosions on adjacent construction sites could cause a similar air pressure change.
Prevention
Q I have read that gluing drywall to the studs is the best way to eliminate nail pops. We have spent thousands on drywall repair ( including the mess! ) repairing nail pops in our present home and I wanted to avoid this in our new home if possible. Also, what is your opinion of screws versus nails. We presently have both screws and nails. Why, and which is best? What type of glue to use?
Thanks for your advice,
Charlie
A We are not in favor of nails at all. It is simply a way that drywall installers can quickly “tack up” a sheet. Usually nails are used on the outer edges of walls and ceilings. When you nail drywall, you are actually smashing the drywall with your hammer so what is actually holding the heavy sheet is the paper face. The better option is to use screws and glue only. A screw spins through the rock and basically drills itself a hole and as long as the edge of the screw doesn’t tear the paper then the head of the screw is holding not just the paper but also the rock.
Nail pops happen because as wood dries, it shrinks. Nails do not shrink. Actually, nails do not pop. The wood stud shrinks away from the back face of the drywall as it dries. The average moisture content of studs is usually 20% during new construction, and reaches an equilibrium moisture content of 10% or less, once the house is dried in. Studs generally don’t get shorter, but they get thinner in thickness and in width, most times shrinking up to 1/8″ as the wood goes from 20% to 10% moisture. Why can’t you get dry wood for your studs? There are various reasons, but basically it relates to time and cost, and Cost is passed on to homeowners, but here is a simple solution:
Place dehumidifiers in the house after framing , but before drywall is installed. You need to shrink and fit the wood to the equilibrium moisture before hanging your wallboard. We suggest hooking a hose to the dehumidifiers, because water will generally run steady for a few days or until the wood is sufficiently dry (10% moisture). At that point you are ready to hang your wallboard.
