Why Do Some Houses Get Icicles on the Roof & Others Don't?

Causes

• Icicles usually form when warm temperatures within your roof melt accumulated ice or snow on your roof's exterior. The frozen water and snow melt, allowing water to drop over the sides of your gutters and the edge of your roof. Heat escaping through your roof during the winter months, coupled with the presence of a layer of snow on the roof, is the main cause of icicle formation.

Effects

• Icicles may be a sign that an ice dam is building along your roof overhang or eaves -- the portion of the roof that extends beyond your home's exterior walls -- according to the The New York Times. Melting water can do two things when it pools behind an ice dam: drip down to form icicles or back up under your shingles, where it rots your roofing materials and causes water damage to your home's interior, according to the University of Minnesota Extension. The extension suggests you make a channel in the ice dam using warm water to direct water off of the roof.

Fixes

• Ventilation is a temporary fix if you have a warm attic space, notes the The Boston Globe's "Handyman on Call," Peter Hotton; however, the general contractor for "This Old House" suggests you should keep your attic cold to stop problems before they start. Seal any air leaks between lower floors and your attic. Your home's exhaust systems, chimney and other heating ducts are other possible causes of a warm roof or attic space. Ensure your home is properly insulated. You may need to increase the amount of insulation between the rafters of your attic or allow a dead airspace between your roof and the insulation, notes the general contractor for "This Old House." Your local utility company may be able to offer solutions to your problem and assistance if you cannot afford to fix the problem yourself.

Warnings

• You should not try to knock down the icicles that form on your home. In attempting to knock down icicles, you may cause damage to your roof or roof drainage system, and the icicles may fall on you, causing injury. Instead, remove the snow from your roof using a roof rake. This will help prevent new icicles from forming. Perform this maintenance from the ground, not from up on your roof. Do not use salt to melt the ice. Salt can damage your roof and plants growing around the perimeter of your home.