What is a common cause of a blister on a flat roof?

A blister on a flat roof typically occurs due to moisture trapped under the roofing membrane. This moisture can originate from various sources, such as rain, condensation, or leaks, and when it gets trapped, it creates a pocket of air that expands with temperature changes. The trapped moisture can cause the roofing material to bubble or blister, which may lead to further damage if not addressed.

Proper installation and ventilation are essential in preventing moisture buildup under a flat roof. While other factors like insulation, heat exposure, and roofing materials can influence the overall integrity of the roof, they are not direct causes of blistering. This is why moisture associated with improper drainage or sealing is regarded as the primary reason for blisters forming on flat roofs.