Shingle Damage Evaluation – Characteristics of Aging – Part 4b

Posted by in Shingles | June 04, 2012

This post is Part 4b of Shingle Damage Evaluation and follows Characteristics of Aging- Part 4a.  Part 4 consists of five short lists.

Characteristics of Aging

The following is the second of five lists of characteristics exhibited by aging asphalt shingles:

  1. Breakage – Breakage is the complete dislodging and separation of a portion of shingle due to the fracturing of the shingle mat from the normal aging, embrittlement, weathering and/or deterioration of the shingle over the years.  Breakage may be accelerated by heavy foot traffic and/or hand lifting of an already aged, brittle, deteriorated, and weathered shingle.  Breakage may result in immediate loss of water shedding ability.  If breakage is due to degrading of the shingle material from normal or premature aging, it has little effect on the potential service life of the shingle because the shingles are already beyond their service life.  Corner breakage is usually due to the lifting of a corner of a brittle shingle with one’s finger or the dog ear bending at the corner when the bundle of shingles was dropped on its corner.


severe deterioration and breakage

SDE-11 Severe deterioration and breakage.


corner breakage

SDE-12 The shape and size of corner breakage causes it to sometimes be mistaken for hail damage.


corner breaks multiple

SDE-13 Multiple corners broken after weakening by bending when the bundle was dropped on its corner.


  1. Clawing – Clawing is downward curling at the corners of the shingles.  Clawing commonly occurs when the bottom of the shingle shrinks relative to the top of the shingle.  Clawing is increased by the exposure of the bottom side of the shingle to excessive heat from a poorly ventilated attic.  Clawing immediately restricts the water shedding ability of the shingle and reduces the potential service life of the shingle because it creates humps that may act as a dam that allows water to accumulate and soak into the shingle.  Prolonged rainfall onto a shallow slope with clawed shingles may allow penetration of ponding runoff soaks through the shingles.  Shingles are not water tight like a swimming pool membrane.  Ponded runoff also exposes the asphalt and mat directly to the deteriorating effects of prolonged contact with water.



SDE-14 Shingles exhibit shrinkage and clawing.


  1. Cracking – Cracking of shingles appears as relatively straight line fractures in the shingles.  Cracking is due to the normal aging, shrinkage, embrittlement, weathering, and/or deterioration of the shingle over the years.  Cracking is especially promoted where the shingle is stretched and the asphalt is exposed by the bending of the shingles over a ridge, staples, or other discontinuity in the surface of the roof deck.


cracked shingle

SDE-15 Shingle exhibits cracking at buckle.


The next post will discuss three more characteristics exhibited by aging asphalt shingles.