Few forces pose as much threat to your roof as winter itself, especially when it comes to the development of ice dams. An ice dam is the result of poor roof ventilation and a warm attic. It can be dangerous when left alone, so you might want to have your roof inspected for problem signs as soon as possible.
Essentially, an ice dam forms when very cold winter days are followed by thaw either via a warm attic or from the weather. Hence, they are common between winter and spring. As the thaw rolls by, the snow on top of your roof melts and runs into the bottom, only to re-freeze into ice on the way down. As Bob Formisano explained in About.com:
Ice dams form when melting snow on a roof refreezes at the edge of a roof. Why does snow melt on your roof when it’s freezing outside? OK, fair question. Well, it melts because the underside of the roof in the attic is above 32 degrees Fahrenheit that it warms the outside roof surface to the point that snow melts. Now here’s the weird part. Ice dams start or get worse after a heavy snow because of its insulating properties. Since snow is such a good insulator the outside roof surface is able to warm up easier from the warm attic space, thereby melting the snow faster.
At the outset, ice dams will cause your roof decking, rafters and sheathing to rot and weaken, significantly reducing the life of your roof. When the weight of the ice becomes too heavy, your roof could cave in. A more pressing problem comes when the icicle formation on your roof gets worse and forms into gigantic daggers of frozen water. This poses a deadly threat to you and your family.
Proper ventilation can prevent ice dams. Get rid of heat sources in the attic. Ensure that the attic space of the roof is well ventilated. Check that the underside of the roof deck is close to the temperature of the exterior side.
One of the best ways to prevent ice dams and other winter-borne roofing problems is to seek the help of dependable roofing contractors in Hampton Roads. These professionals can inspect, maintain and repair your roof before problems get worse. Many reliable contractors, like those from The Roofing and Remodeling Company have the experience and expertise to attend to your needs.
(Info from Ice Dams: How to Prevent and Remove Them, About.com Home Repair)