What does the term "ice dam" refer to in roofing?

The term "ice dam" specifically refers to a blockage caused by melting and refreezing water at the eaves of a roof. When snow on the roof melts due to heat escaping from the building, the water runs down the roof until it reaches the colder edges, where it freezes once again. As this process continues, ice accumulates, forming a dam that prevents further melting snow from draining off the roof. This trapped water can back up under the roofing materials and potentially leak into the building, leading to water damage.

Understanding that an ice dam is associated with both melting and refreezing is crucial for recognizing how to prevent and address this issue, especially in climates that experience snowfall. Other concepts related to roofing materials and configurations, such as pooling water under shingles or a build-up of ice on the roof ridge, do not accurately describe the phenomenon of an ice dam and its implications.