The Reasons for Icicles Outside Your Home

Ice Dams

• Ice dams are the cause of many icicles hanging from houses. When snow piles up on the roof and the weather stays cold, the snow in direct contact with the roof may melt. The water runs down the roof under the eaves, protected by the blanket of snow. Once the water reaches the colder eave, it refreezes. When this action is repeated many times, an icy hump forms that holds snow against the roof instead of allowing it to melt normally.

Ice Dams and Icicles

• Icicles can form as a result of growing ice dams. As the ice dam expands, water droplets accumulate, eventually pouring off the surface. The water droplets are robbed of their heat and become attached to the ice dam as gravity pulls them downward. Many droplets piling atop one another cause the familiar shape of the icicle.

Preventing Ice Dams

• Add at least a foot of new insulation to attic floors or increase ventilation to attics to reduce the risk of ice dam formation. If ice dams have already formed, remove the majority of snow from the roof with a roof rake, which allows you to safely clear accumulated snow from the ground. Do not attempt to break up ice dams if they form as you can easily damage roofing materials, but removing snow will slow their growth.

When Icicles Mean Trouble

• The action of melting snow and the ice dams that contain it can cause structural damage to your home. Backed up water can leak into attics or down the sidewalls of the home. These innocuous water droplets eventually lead to significant rot of wooden posts and beams.