In the following, I quote from one book , *Drywall Application, *of a 13-14 book Builder’s Series put out in the mid 1980’s by Canada’s national housing agency, Canada Moprtgage and Housing Corporation. If there is excessive moisture and air humidity in a building, the condition may lead to sagging or wavy ceilings in properly installed drywall. No where do they mention excessive interior moisture as a cause of nailpops.
Their format is as follows:
PROBLEM- Sagging or wavy ceilings
CAUSE - Excessive moisture and humidity
Texture spray too wet; high humidities (my ed.- from spray painting)* and poor ventilation during construction; moisture in attic. Moisture absorption will soften the gypsum core.*
PROBLEM- Nail pops
CAUSE - Wet framing lumber
Framing lumber should not exceed a moisture content of 19% (the maximum allowed by the National Building Code). However, in many parts of the country, and particularly in Eastern Canada, the moisture content of framing lumber is often much higher. As this lumber dries to 12-14% (6-9% in mid-winter and in drier climates) shrinkage occurs , the stud pulls away from the gypsum board, and any subsequent movement of the board causes the nail to “pop”. A 10% change in moisture content can cause a spruce or fir stud to shrink up to 1/4"
CAUSE - Misaligned or warped studs
CAUSE - Fastener length or type
Longer fasteners actually worsen the problem of nail pops, since shrinkage takes place over a greater length of nail.
CAUSE - Fastening techniques
It can be difficult to hold the board and nail at the same time. Thicker insulation often prevents good contact between the board and framing.
CAUSE - Vibration
Exterior fastening of brick ties, siding or trim can loosen drywall nails
From this article:
“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.”
The highlighted text seems to confirm my theory stated in an earlier post!!