Asphalt Roofing and Failure Mechanisms


Asphalt shingles are composed of a base of fiberglass. An asphalt coating and surface granules. The base material gives the roofing material its strength. The asphalt in the roof shingle provides the ability to resist weathering. The granular material adds protection to the roof shingles so they stand up to the ultraviolet rays of the sun.

These types roof coverings have a life expectancy of fifteen to twenty years. There are those who believe that these new asphalt roof shingles can last over forty years. A more realistic life expectancy is twenty years based on current data.

Adverse climates: Colder and wet weather conditions will significantly reduce the life expectancy of asphalt roofing. The more stable the environment and weather the longer life the roofing material is likely to have. Harsh environments will wear out asphalt roof shingles prematurely.

Manufacturing defects: The manufacturing process can contribute to reduced life expectancy of asphalt roofing materials. One of the defects that can exist is thermal splitting. This defect causes the roof shingles to crack prematurely. Thus the roof covering will have a marked shorter life expectancy.

Ventilation: Ventilation plays a major role in increasing the life of an asphalt roof. Roofing with adequate and well thought out ventilation should have a longer life then roofs with poor ventilation. Proper venting allows the attic and underside of the roof to be cooler. Because the roof covering is cooler its life expectancy should be longer. Proper venting can be achieved by installing roof ridge vents, gable vents, soffit vents and automatic attic vent fans.

Sunlight: The more sunlight (ultraviolet rays) a roof receives the shorter its life will be. A roof covering that is not exposed to direct sunlight will have a longer life expectancy.

Building and construction factors that can effect asphalt shingle life:

Roof shingles will last longer on steeply pitched roof structures because rain and snow sheds easily. On a steep roof there should be no areas of ponding water. Low slope roofs do not shed water quickly and as a result will have a shorter useful life.

Manufacturing factors also have a role in the life expectancy of asphalt roofing.

A. Shingle thickness- As a rule the thicker the asphalt material the greater its useful life.

B. Color- Lighter color roofing materials as a rule will deflect ultraviolet rays as opposed to absorbing it. Lighter color roof shingles will have a longer life then the darker colored roofs.


Source by John Martino