Ice dams are horizontal ridges of ice that form after a snowfall. These ridges prevent melting snow from getting to the gutter system. This water refreezes and the problem quickly compounds and will eventually cause physical damage.
The Cause – often poorly ventilated homes leak heat into the attic areas. This warm air is now in direct contact with roof that is supporting the snow. The snow will melt and begin to drain, until it passes to an area of the roof without a heat source. This water instantly freezes. It usually occurs directly above the supporting exterior wall and just above the gutter line.
Clogged gutters do NOT cause an Ice Dam, but they will make the problem worse. Dangling icicles are symptoms of both Ice Dams and/or clogged gutters.
Poor attic ventilation will cause an Ice Dam to form. Once formed, an Ice Dam continues to grow with every thaw/freeze cycle
The Ice Dam prevents real drainage, causes dangerous icicles, adds unwanted weight to the roof and will eventually cause roof damage
One part of the Western Mass Gutter Monkey winter maintenance program is to shovel roofs and put calcium chloride on the ice to melt it away.