Everything You Need to Know About Ice Dams

Icicles hanging down from roof eaves


When icicles begin to form on your roof during the winter, you probably don’t think twice. They’re a natural symbol of the winter season, and they’re also pretty cool to look at it. But icicles form under the same conditions that produce ice dams, which can cause serious trouble to your roof. In this blog, we’ll look at what ice dams are, how they form, and ways you can prevent them from damaging your roof.


What is an ice dam?

An ice dam is a build-up of solid ice that forms along the edges of a roof. This phenomenon got its name because the ice acts as a dam; it prevents water from flowing off of the roof. The presence of gutters usually only furthers an ice damming problem, but they can also form on structures without gutters.

Ice dams form after snow accumulates on the roof after a snowfall. Warm air from inside the home rises, eventually reaching the attic and warming the roof. The warm air causes the snow to melt and run down the roof. When the water reaches the eaves, which do not get warm like the rest of the roof, it refreezes, forming a wall of ice. This ice barrier builds up and forms a dam, which causes melted snow from other parts of the roof to back up behind it. This backed up water can seep through the shingles and cause extensive water damage to the home.


It’s nearly impossible to keep all heat from escaping through the roof, but there are three main causes that will lead to ice damming:

  • Poor insulation in the attic
  • Poor ventilation
  • Gaps between living space and attic

Keep in mind that a roof is designed to shed water, not hold freestanding water. If water pools on a roof due to ice damming, it can lead to interior problems like damaged walls, rotten wood, and even mold growth. The easiest way to deal with ice dams is to prevent them from happening in the first place. To prepare your roof from ice dams and save on energy costs, you should have a professional:

  • Install or repair attic insulation
  • Seal any air leaks in the attic
  • Properly ventilate the attic

Some people recommend physically removing snow from your roof with a roof rake after a storm, but we advise against this, as it can be very dangerous. If you believe your attic is not properly equipped for snow this winter or notice ice dams forming after storms, contact Blackstone Exteriors to diagnose the issue and provide you with an expert, cost-effective solution!