When shingles curl, it means the asphalt shingle is experiencing physical distortion due to aging, moisture imbalance, or ventilation problems, and is nearing the end of its effective waterproofing life. There are two main types of curling. Cupping occurs when the edges of the shingle turn upward, forming a concave shape, often caused by the top surface shrinking faster than the bottom due to UV exposure and loss of protective oils. Clawing occurs when the middle of the shingle rises while edges stay flat, often caused by moisture absorption in the mat. Both forms indicate that the shingle is no longer lying flat and cannot properly shed water, as curled edges allow wind-driven rain to get underneath and cause leaks and wind uplift. Common causes include natural aging after 15 to 25 years, inadequate attic ventilation that causes excessive heat buildup cooking the shingles from below, improper installation with too few nails, or manufacturing issues. Curling is not just cosmetic, it significantly reduces wind resistance and waterproofing ability. A few curled shingles can be temporarily repaired with roofing cement, but widespread curling across the roof is a clear sign that the roof system has failed and needs replacement, and ventilation should be corrected at that time.
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