NRCA has received a significant number of complaints from contractors stating manufacturers claim a relationship between improper fastener placement and asphalt shingle failures. As a result, NRCA conducted a limited study of architectural, laminated asphalt shingles commonly used in the U.S. roofing industry. One of the study's purposes was to provide some background data for use by NRCA in developing appropriate nail placement tolerances for such shingles.
The current situation
Asphalt shingles enjoy widespread acceptance in the U.S. roofing industry. During the past several years, architectural, laminated asphalt shingle use has surpassed the use of conventional three-tab strip shingles and now is more than half of all asphalt shingle products installed.
In 1998, NRCA began looking into application tolerance guidelines for three-tab strip shingles. This investigation spurred from reports by NRCA-contractor members that several manufacturers were claiming improper fastener placement during application was a reason for failures in specific asphalt shingle roof assemblies. (For additional information regarding fastener placement tolerances, see "Asphalt shingle application tolerances," March 2000 issue, page 106).