Shingle Damage Evaluation – Functional Hail Damage – Part 5a

Posted by in Shingles | July 09, 2012

This post is Part 5a of Shingle Damage Evaluation and follows Characteristics of Aging- Part 4e.

Functional Hail Damage to Composite Asphalt Shingles 

Industry standards and studies have defined functional hail damage to asphalt shingle roofs as a diminution of the water shedding ability of the shingle or the reduction in the long-term service life of the shingle.  (Diminution is a 50 cent word meaning “a decrease or diminishing.”)  This definition is based upon many years of research and testing and has been published in peer-reviewed literature.

Functional hail damage to asphalt shingle roofs is characterized by a localized loss of granules, usually circular in shape, and a fracture in the mat.  A fracture in the mat is evidenced by a visible relatively clean fracture, an indentation in the mat of the shingle, and/or localized softness in the mat.  Industry studies have shown that softness in the mat, commonly called a bruise, is indicative of a fracture on the bottom side of the shingle or in the mat.  Hail damage can be detected immediately after the hail impact either by visual observation and/or by tactile examination of the shingles by one who is properly trained and experienced in the identification of functional hail damage.


hail damage in shingle 1

SDE-29 Shingle exhibits light granule at fracture in mat.


hail damage in shingle 2

SDE-30 Shingle exhibits light granule loss at fracture in mat.


hail damage to shingle 3

SDE-31 Cap shingle exhibits fracture in mat at poorly supported bend.


It is claimed by some that damage from hail impact may cause a gradual loss of granules that can result in premature aging of the shingles over time. They further claim that without visible damage, there is no real way to be sure how much damage shingles have sustained and that the damage may not be apparent until months or years later.  Industry studies disagree.

Granule loss alone, such as evidenced by granules in the gutter or widespread and relatively uniform loss of granules on the shingles, especially the gradual loss of granules over time, is not evidence that the shingles have been functionally damaged by hail.  The progressive loss of granules is considered normal wear and tear.  Granules are commonly dislodged when the shingles are exposed to heavy rainfall, wind, small hail impacts, and normal foot traffic.  Furthermore, long term tests by Haag Engineering of Dallas, Texas have shown that even spots of granule loss from hail impacts do not affect the long-term service life of the shingles, unless there is a coinciding fracture or bruise.

Examining composite asphalt shingles for hail damage includes research into the size and direction of the hail stones by surveying other nearby objects and building components for physical evidence left by the hail impacts.  These will be discussed in the next post.