Final answer:
Ice damming is primarily caused by improper insulation and ventilation in a home's attic, which leads to snow melting on the roof and refreezing at the eaves, forming a dam that prevents water from draining properly.
Step-by-step explanation:
Ice damming usually occurs due to improper insulation and ventilation in a home's attic. This situation arises when warmth from the house escapes into the attic, melting the snow on the roof. The melted snow then runs down the roof to the eaves where it refreezes because the eaves extend past the side of the house and are not warmed by the household heating. Over time, this creates a dam of ice that prevents proper drainage of water off the roof, leading to potential water damage to the home.
While too much snow with long-term low temperatures can contribute to conditions that support ice damming, and issues such as improper pitch, worn roofing, or incorrect flashing can exacerbate problems, the most common cause is typically related to inadequate insulation and ventilation. Appropriate insulation and ventilation will minimize the transfer of heat to the roof, thereby reducing the chances of snow melting and refreezing at the eaves.