A roof slope below which measurement may likely allow ice to back up under the shingles?

A roof slope of 2/12 is significant because it is the critical threshold below which ice dams are more likely to occur. In roofing, a slope of 2/12 means that for every 12 horizontal units of distance, there is a 2-unit vertical rise. This relatively low slope does not facilitate effective water drainage. When snow or ice accumulates on a roof with this low pitch, the melting snow can flow down toward the eaves. However, if the temperatures are cold enough, this melted water can refreeze at the eaves, leading to the formation of ice dams. These ice dams can prevent further drainage, causing water to back up under the shingles and potentially lead to leaks and water damage inside the building. Maintaining a steeper pitch helps promote drainage and reduces the risk of ice dam formation.