What is an ice dam, and how does it form?
When snow accumulates on a roof, a cycle of melting and refreezing occurs. In a perfect world, the snow would melt off the roof, enter the gutters, and flow harmlessly to the ground. Or the snow would evaporate from the action of the sun, and never really melt off unless the outside temperature rose above the freezing point. However, two key factors interact to cause problems… the outside temperature and the temperature of the inside of your attic. The warmer your attic is, the more melt off that occurs at the roof surface. This melted snow would normally flow off the edge of the roof. Under certain conditions, though, when air temperature is very low, the water refreezes at the edge of the roof, where the interior roof surface is not being warmed by the attic. This refreezing gradually forms what is fondly known as an “ice dam”, a growing heap of ice that blocks path of the melted snow. Once this dam forms to a certain height, the melted snow that pools up behind it can suddenly lea
