What is an ice dam?

Ice dams are the shelves of ice that often build up on the edges roofs after snowstorms, when freezing temperatures move in, according to the Federal Emergency Management Agency. They can cause damage to roofs and water leaks inside your home. Ice dams also prevent snow from sliding off roofs, allowing it to pile up more.

A graphic of how an ice dam forms. (Courtesy FEMA)

What causes ice dams to form?

Ice dams are caused by snow, heat and cold. First snow falls on the roof. Then heat from inside a home melts some of the snow. The melting snow runs down the roof and the outside cold refreezes it. This builds up and forms an ice dam.

How do you prevent ice dams?

The best way to prevent ice dams is with adequate attic insulation and roof ventilation, and to make sure air leaks in the attic are sealed, according to FEMA. Ideally, this should be taken care of when the house is built. It can be done at later points by professionals, especially as part of roof repair or remodeling.

How do you remove ice dams?

Remove snow from your roof using a roof rake. This should be done after snow falls to avoid ice dams.

Here are some safety tips for removing snow.

– Fill a pantyhose with calcium chloride with and lay it perpendicularly across the ice dam.

“It can in certain conditions eat its way down to forming a channel for the backed up water to get through,” Bruce Irving, the former executive producer for “This Old House,” told Radio Boston.

Here is a guide to getting rid of ice dams from “This Old House.”

– Chipping or chiseling away icicles and ice dams is another option, but it needs to be done carefully. Still, this can be damaging to your roof and the falling ice can be a hazard. It may best to seek a professional to do this.

– Call a roofing professional to take care of the whole thing. This is likely the best and safest bet to get rid of an ice dam.