The Most Common Asphalt Shingle Defects and What They Mean for Your Roof

Asphalt shingles are designed to protect your home for many years, but they are not immune to wear and manufacturing or installation defects. Understanding the most common shingle problems can help homeowners recognize early warning signs before minor issues turn into costly roof failures.


Granule loss is one of the most noticeable defects. Granules protect shingles from UV damage and weather exposure. When excessive granules collect in gutters or at downspout outlets, the underlying asphalt becomes exposed and deteriorates rapidly. This shortens shingle life and increases the risk of cracking and leaks.


Thermal cracking, sometimes called craze cracking, occurs when shingles repeatedly expand and contract from temperature changes. Over time, fine surface cracks form and gradually deepen. These cracks weaken the shingle surface and allow moisture to penetrate, especially in colder climates (like here in Johnstown, PA) with frequent freeze-thaw cycles.


Blistering appears as raised bumps on the shingle surface caused by trapped moisture or air within the shingle layers. When blisters rupture, they leave exposed areas that are vulnerable to water intrusion and accelerated deterioration. Blistering is often linked to manufacturing defects or poor attic ventilation.


Buckling occurs when shingles form ripples or waves instead of laying flat. This is usually caused by movement in the roof deck, moisture-related expansion, or improper installation. Buckled shingles disrupt water flow and create areas where wind-driven rain can easily enter the roofing system.


Curling happens when shingle edges or corners lift upward or downward. This defect is commonly associated with aging shingles, moisture imbalance, or improper ventilation. Curled shingles are more likely to catch wind, break off, and allow water to reach the underlayment beneath.


Edge wear develops when shingles experience prolonged exposure to wind, debris, and weather. The edges begin to thin, fray, or deteriorate, reducing their ability to properly shed water. This often leads to leaks along roof edges and in vulnerable roof valleys.


Other defects include fishmouthing, where shingle corners lift and form gaps, and delamination, where the shingle layers begin to separate. Both conditions significantly reduce the roof’s protective ability and usually indicate that replacement is approaching.


While some shingle defects are related to age, others point to installation errors, ventilation problems, or manufacturing issues. A professional inspection can determine the cause and help homeowners decide whether repairs or full replacement is the best option.


Recognizing these warning signs early allows you to protect your home, avoid interior damage, and extend the life of your roofing system through timely and informed decisions.


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