NRCA has expressed concern about the lack of practical tolerance guidelines governing the placement of fasteners used to attach asphalt shingles. Recently, there have been some notable developments regarding this issue, which I will discuss in this column.
NRCA has maintained it is not possible for asphalt shingle installers to consistently achieve fastener placement according to the exacting requirements printed in asphalt shingle manufacturers' installation instructions.
For example, in 2002, NRCA conducted a survey about architectural laminated asphalt shingles. The survey revealed fastener-placement tolerances as little as plus or minus 1/4 of an inch (6 mm) are required by manufacturers to reasonably ensure fastener penetration to a laminated shingle's double-thickness portion. (For additional information, refer to "Asphalt shingle application tolerances," March 2000 issue, page 106, and "Are laminates tolerant?" August 2002 issue, page 30.)