Shingle Damage Evaluation – Characteristics of Aging – Part 4d

Posted by in Shingles | June 18, 2012

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

Characteristics of Aging

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

  1. Embrittlement – Embrittlement is the hardening of the soft asphalt and the shingle mat materials over the years such that the shingle becomes brittle and is susceptible to shattering, cracking and breakage.  Embrittlement occurs as a result of the normal aging and weathering of the shingles over the years; however, it is accelerated by the exposure of the shingle to excessive heat from a poorly ventilated attic.

SDE-20 Shingles exhibit embrittlement.

  1. Flaking (Organic Shingles) – Flaking is the delamination of the upper layer of the asphalt which bonds the granules to the lower layer of asphalt that saturated the organic shingle mat.  Flaking is commonly due to the drying and degrading of the asphalt over the years and the differential movement between the bond coating and the saturated coating caused by the repeated shrinkage and swelling from moisture variations and/or expansion and contraction from thermal variations.  When flaking is somewhat circular in shape, it is sometimes mistaken for hail damage.  However, closer visual and tactile examination disclose that the flakes do not exhibit a fracture or an indentation in the mat (as will be discussed later), but a well defined edge of the remaining second asphalt coating applied to bond the granules.
flaking 1

SDE-21 Shingles exhibit flaking of granules and asphalt bond coating.


flaking 2

SDE-22 Shingles exhibit flaking of granules and asphalt bond coating.

  1. Fractures And Splitting – Vertical, horizontal and/or diagonal fractures or splits in the shingles are due to the thermal expansion or contraction of the shingles and/or the roof deck in combination with excessive restraint of the shingle strip.  Excessive restraint of the shingle strips is commonly due to an inflexible tab sealant.  The combination of the restraint of the shingles by the nails and the sealant with the expansion/contraction of the shingles or the roof deck causes the shingles to be stretched: this is called tension.  When the tension stresses from the stretching exceed the strength of the shingle, it fractures or splits.


splitting overall

SDE-23 Shingles exhibit vertical splitting.SDE-19 Shingles exhibit vertical splitting.


splitting close

SDE-24 Shingle exhibits buckling and vertical splitting.


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