Winter and roofs Ice dams are most common in northern climates that are subject to heavy snow buildups on roofs. Ice dams occur when this heavy snow buildup melts during the day and then refreezes when temperatures fall overnight. After several days of the thaw-freeze cycle, it’s common for the ice to work up under the shingles until it reached an area of the roof warmed by your home. This is when your home becomes vulnerable because that ice begins to melt from your home’s warmth and causes a leak. This leak can potentially damage your ceiling, walls and the contents of your home. The problem worsens because insulation loses its R-Value when it gets wet. In cases where the ice dam goes unnoticed for an extended period of time, there can be significant damage to the building and its contents.