Ask Angie: Preventing ice dams on roofs

Angieslist.comDecember 6, 2013 


Angie Hicks


Dear Angie: What causes ice dams on roofs, and how can I prevent them? — Christine L., Farmington, Conn.

Answer: Those long icicles hanging from your roof might evoke a winter wonderland, but they're often associated with destructive ice dams.

Ice dams form at a roof's edge and in gutters when melting snow refreezes and can't drain off the roof. The dams prevent gutters and downspouts from filtering water away from your home, causing even more of a backup and a larger ice dam.

Heat, ironically, is a major cause of ice dams. When too much heat escapes through the attic, it can melt snow on the roof. The melted snow then refreezes at the roof's edge because that area of the roof isn't receiving attic heat.

Water that collects behind an ice dam can seep through your roof and into your attic and walls, creating structural damage, mold and other problems. Water refreezing beneath shingles causes roof damage.

Homes with lower-pitched roofs are more prone to ice dams because it's easier for water and snow to glide off steeply pitched roofs.

Highly rated roofing and insulation service providers tell our researchers that ice dams are difficult to remove, so the best idea is to take action to keep them from forming.

The main way to prevent ice dams is to reduce the amount of heat escaping through the attic by making sure the attic is sufficiently insulated and appropriately ventilated.

If you still experience ice dams, consider these options:

■ Place a de-icing cable along the bottom of the roof to melt snow.

■ Use a roof rake to knock snow off before it has a chance to melt and refreeze.

■ Put a heating coil on the roof to melt a section of snow, creating a path for water to exit.

If you'd rather not tend to roof snow yourself, consider hiring help. Many landscape companies offer snow removal services in the winter.

In addition, you might consider hiring a roofing or construction contractor to install an ice shield on your roof, which provides an extra layer of leak protection under shingles.

Be aware that trying to eliminate an ice dam with an ax or other tool can damage your roof and gutters. Most highly rated companies that remove snow use steam to remove a dam. The cost for removal can range from $100 to $700, depending on the extent of the problem and the gutter's size or length.

Angie Hicks compiles the best advice from the most highly rated service pros on to answer your questions. Ask Angie your question at

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