Which of the following best describes the condition of a Blister?

A blister in roofing terminology refers to a local raised area that forms as a result of internal pressure, often caused by trapped moisture or air beneath the roofing material. This internal pressure causes the roof membrane to lift away from the substrate, creating a bubble-like formation. Blisters can occur in various types of roofing systems, including built-up roofing and single-ply membranes, and they are generally indicative of improper installation or roofing material failures.

Understanding this definition is crucial for identifying and addressing potential issues in roofing systems. Recognizing blisters early allows for preventative measures to be taken and can help in avoiding moisture intrusion that can lead to further complications like mold growth or structural deterioration.

In contrast, the other choices depict different roofing issues. A buildup of moisture would refer to a saturated roof condition, while peeling surface due to sunlight may be a symptom of UV damage or aging. A sign of structural failure suggests more severe conditions related to the overall integrity of the building rather than localized phenomena like blisters.