Shingle Damage Evaluation – Effects of Aging on Composite Asphalt Shingles – Part 3

Posted by in Shingles | May 21, 2012

This post is Part 3 of Shingle Damage Evaluation and follows Composite Asphalt Shingles.

Effects of Aging on Composite Asphalt Shingles

Like all things in life asphalt shingles degrade and wear out over time.

As asphalt shingles age, the petroleum or other soluble base of the asphalt evaporates through exposure to heat and washes out through exposure to water from rainfall and and snow melt.  This “drying out” of the asphalt causes it to progressively lose its softness, flexibility, and strength.  The loss of softness, flexibility, and strength reduces the ability of the shingle to accommodate thermal movements and resist damage from impacts.

The aging of the shingles and evidence of reduced softness, flexibility, and strength begin with the surface graying and surface hardening of the asphalt.  It progresses with cracking in the asphalt, shrinkage of the shingle especially the tabs, warping or deformation of the shape, granule loss, embrittlement, and breakage.  In extreme cases, the asphalt becomes so brittle, not unlike fresh potato chips, that the shingles may become easy to break or shatter.  Shingles in this condition are clearly in need of replacement and are well beyond their service life.

Fortunately, the loss of softness, flexibility, and strength progresses slowly over a period of time usually measured in years.  The length of the manufacturer’s warranty often provides insight into the expected service life of the shingles.  However, the characteristics of aging may occur prematurely as a result of accelerated deterioration of a poor quality shingle or as a result of exposure to a more severe environment, such as exposure to excessive heat from a poorly ventilated attic or poorly ventilated rafter spaces.

The characteristics of aging will be looked at in more detail in the next post.