Buckling and curling When a shingle buckles, it bends upward in the middle, forming a peak. Curling causes the corners of the shingle to turn up, and is usually caused by a lack of ventilation, nails positioned too high up, an incorrect number of fasteners or under-saturation of the shingle. Blistering and rotting Blisters are bubbles that appear on the surface of asphalt roofing. They are usually caused by moisture in the shingle. Shingles rot when the mat at the core of the shingle absorbs moisture.
Ice dams occur on roofs with inefficient insulation and cold eaves.
In winter, snow accumulates on roofs. As it melts down to the overhang and refreezes, an ice dam is formed. An ice dam can be detected by long icicles on overhangs. Ice dams cause water backups, allowing water to seep through the roof and cause even more damage. In addition to preventing ice dams, insulation can also help reduce energy bills and keep homes cooler during spring and summer.