Thermal cracking: This not so common defect is caused by the fiberglass mat being too thin. As a result it becomes more vulnerable to tearing. The bonding adhesive that helps prevent uplift may be too strong. This will allow one continuous flow of roofing materials without the required room for some expansion and contraction and movement. These defects contribute too more roof shingle damage and wear. When these defects are present any changes in weather conditions will significantly effect the useful life of the roof.
Cupping: Roofing shingles gradually lower in the center and raised at the ends, almost like a U-shape. Cupping is a signs of an older and well worn shingle roof. Cupping is a normal wear pattern that progressively gets worse as the roof get older. A cupped roof surface will be very fragile and should not be walked on because major damage will occur to the asphalt shingles
Granular loss: The purpose of the granular material on top of the mat is to protect the asphalt shingle from ultraviolet rays. These granules give the asphalt roof covering its color. Some loss of protective granular material is normal. This normal condition can sometimes be viewed as granules laying in the bottom of the gutters. As the roof gets older granular loss may increase where ultimately areas of roof mat are fully exposed to the elements. These exposed sections of shingle mat will wear out at a much greater rate because of the exposure to ultraviolet rays and other weather conditions.
Curling: Another condition that becomes worse with age is curling. The edges of the roof shingles curl under as the roof ages. As with a roof that is cupping the curling roof is very brittle. A roof that is curling requires replacement as soon as possible in order to avoid water infiltration.
Fish mouthing is a roof wear indicator where the space in between the tabs of the shingle spreads apart and becomes wider at the bottom of the shingle then the top. Fish mouthing condition exists when the roof shingle above the key way under it raises up and looks like an open fish mouth. Fish mouthing is usually bought on by high moisture conditions inside the building and poor roof venting. Having this wear/ indicator points too a larger issue within the dwelling as opposed to normal roof shingle wear.
You should think about replacing your asphalt shingle roof if it is showing any of these signs of wear. Always make sure that your roofing contractor installed adequate roof venting in order to help prolong the useful life of your roof.