Shingle Damage Evaluation – Characteristics of Aging – Part 4a
This post is Part 4a of Shingle Damage Evaluation and follows Effects of Aging on Composite Asphalt Shingles. Part 4 consists of five short lists.
Characteristics of Aging
The following is the first of five short lists of characteristics exhibited by aging asphalt shingles:
- Balding – Balding is the extensive loss of granules such that the underlying asphalt coating is exposed. Balding is the result of normal aging and weathering of the shingles over the years, but it is accelerated by inadequate bonding of the granules to the asphalt coating, repeated scuffing from excessive foot traffic, prolonged wetness, and/or some other manufacturing defect. Balding usually does not result in immediate loss of water shedding ability, but it reduces the potential service life of the shingle because the asphalt is exposed directly to the deteriorating effects of prolonged contact with sunlight and water.
- Blistering – Blistering appears as bubbles on the surface of the shingles or small relatively circular cavities that penetrate into the asphalt. Blisters are due to the vaporization and expansion of the volatiles, such as, kerosene or water, in the asphalt. The vaporization and expansion occur when the shingles are heated by ambient temperatures, the radiant heat of sunshine, and/or excessive heat from poorly vented attic. When the blisters of the bubble break or are worn away by normal weathering or foot traffic, a cavity is exposed in the asphalt. Blistering is the result of a shingle manufacturing anomaly, but is commonly increased by exposure of the shingles to excessive heat from a poorly ventilated attic. Blistering usually does not result in immediate loss of water shedding ability, but it reduces the potential service life of the shingle: when the blisters break, small spots of the asphalt and mat are exposed directly to the deteriorating effects of prolonged contact with sunlight and water.
- Buckling – Buckling is the localized heaving of the shingle surface due to the expansion and/or the swelling of the shingle mat in combination with the restraint of the shingle mat by the roofing nails, an adjoining shingle, and/or the asphalt sealant. Buckling that extends side to side on a shingle tab immediately restricts the water shedding ability of the shingle and reduces the potential service life of the shingle because it creates a ridge that may act as a dam that allows water to accumulate and soak into the shingle. Prolonged rainfall onto a shallow slope with buckled 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.