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
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'
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...
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