Which type of roof is most prone to ice dams?

The type of roof most prone to ice dams is low slope roofs with wide soffits. Ice dams typically form when snow on the roof melts due to heat escaping from the living space below, then refreezes at the eaves, creating a barrier that prevents subsequent meltwater from draining off the roof.

Low slope roofs are particularly susceptible to this phenomenon because they do not allow for efficient runoff. The water that pools as a result can easily freeze, creating an ice dam. Additionally, wide soffits can trap air and retain heat, further exacerbating the melting of snow near the peak of the roof while the edges remain cold. This combination of conditions makes it likely for ice to accumulate and create problems that lead to water backing up under shingles and potentially causing leaks.

In contrast, steep pitched roofs allow melted snow to slide off more easily, reducing the opportunity for ice dams to form. Flat roofs can sometimes experience pooling but are generally designed to manage drainage effectively with built-in slopes, and high slope roofs with skylights are less likely to create the same conditions for ice dams due to their angled nature and possibly improved air circulation around the skylights.