Finite element analysis of racked vs. traditionally applied three tab, seal tab, strip shingles, and blister tests for asphalt-glass pelt shingles

This paper compares the stresses developed by wind and by; a sudden drop in temperature, using finite element analyses on three tab, self-sealing, asphalt-glass fiber felt shingles, that are rack installed (with three and four nails per shingle in alternate tiers), with the same shingles that are conventionally installed (diagonal lay-up, with four nails per shingle). From these studies, we concluded that the nailing pattern is not significant, as long as the shingle tabs remained sealed. We confirmed these conclusions using our wind tunnel and environmental chamber on commercially produced shingles. As a separate and unrelated matter, this paper also discusses the evaluation of blistered asphalt-glass fiber felt strip shingles using digital fluoroscopy, and the results of several laboratory tests that are intended to measure the blistering tendency of asphalt coated products.