Shingle Damage Evaluation – Characteristics of Aging – Part 4c
This post is Part 4c of Shingle Damage Evaluation and follows Characteristics of Aging- Part 4b. Part 4 consists of five short lists.
Characteristics of Aging
The following is the third of five lists of characteristics exhibited by aging asphalt shingles:
- Craze (Map) Cracking – Craze or map cracking of shingles appears as a pattern of roadways similar to a map. Crazed cracking is the result of the normal deterioration of the asphalt coating of the shingles from aging over the years. When the asphalt material dries, shrinks, and weathers from normal exposure to water and sunlight it is randomly stretched. The random stretching of the asphalt causes it to crack in a random pattern.
- Cracking & Granule Loss In Asphalt Overlay (Appliqué Shingles) – Widespread cracking and irregular, but sometimes circular, shaped areas of granule loss in the surface of the shingles at the asphalt overlay result from the excessive differential shrinkage of the asphalt overlay and the poor bonding of the asphalt overlay to the underlying layer of granules during the manufacturing process. The extra thickness of asphalt at the overlay or appliqué also makes the shingle surface more susceptible to cracking when the upper asphalt coating shrinks more than the lower asphalt coating. Cracking and granule loss are evidenced by the pattern of widespread granule loss and cracking in the surface of the asphalt overlay, but usually not seen in other surfaces of the shingles. One shingle manufacturer has issued a technical bulletin regarding this phenomenon and notes that it does not affect the function or service life of the shingles.
- Curling And Cupping – Curling and cupping are the upward lifting at the corners and edges of the shingles. Curling and cupping occur as a result of the swelling of the underside of the shingle relative to the top of the shingle and/or the shrinkage of the top surface relative to the underside of the shingle. The swelling of the underside of the shingle is commonly due to the migration of excessive amounts of airborne moisture from the attic spaces through the roof deck and into the bottom surface of the shingle. The shrinkage of the top surface is commonly due to normal aging and weathering of the shingle over the years.