Uniformly Spaced Spots of Granule Loss on Shingles
There are a number of causes of spots of granule loss on shingles. In this article we look at a manufacturing defect.
Note the relatively uniform spacing of the spots of granule loss in Figure 1. Note also the consistency in the pattern of their location on the shingle and their relatively consistent size.
This type of damage is due to the poor bonding of the granules to the shingle mat. The poor bonding is probably due to some type of contamination from the roller, as evidenced by the relatively uniform spacing of the spots of granule loss.
The granules bonded well enough for the shingle to appear acceptable at installation, but over time a patch of granules are separated from the surface of the shingles during normal weathering.
These types of spots of granule loss are sometimes mistaken as hail damage, but they do not exhibit an accompanying fracture or bruise in the mat (see featured photograph at top).