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 down your rain spouts. 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 the snow will melt at the roof surface. Under certain conditions, 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 known as an “ice dam”, a growing heap of ice that blocks the path of the melted snow.
 
Once this dam forms to a certain height, the melted snow that pools up behind it can suddenly leak back under the roof shingles and into your home! On a roof with a low slope, it only takes a small ice dam to cause water backup and leakage.
 
Removing the snow from your roof is definitely one way to help prevent ice dams. For help in determining if you can prevent an ice dam more permanently through changes to your roof or attic, please talk to a reputable roofing contractor.