Ice Dams

‘Ice dam’ – When you see those words, do you think of ice causing problems for the flow of water in a river?  You’re right about the river, but an ice dam is also a build-up of ice that forms at the edge of a roof. It prevents melting snow (water) from escaping off the roof. That water can back up and leak through the roof damaging insulation, ceilings, paint etc.

The large amounts of snow we’ve seen this winter combined with deep cold and then thaws, make for the perfect conditions for an ice dam on your roof.

How are ice dams formed?

For an ice dam to form, there must be a layer of snow on the roof. Heat from an improperly ventilated or insulated attic melts the snow and water starts to run down the roof. The water gets trapped in the deep snow at the base of the roof or in clogged eavestroughs and freezes, forming the ice dam. When the dam forms, it blocks further melting snow or water from escaping. The trapped water then finds ways of leaking through shingles and/or weak spots in the roof causing damage.

The following diagram from the University of Minnesota shows an ice dam and how the damage is caused.

How ice dams are formed. Diagram from the University of Minnesota extension.

Preventing Ice Dams:

‘An ounce of prevention is worth a pound of cure.’ The Benjamin Franklin quote holds true. These tips should help to prevent costly damage caused by ice dams:

  • Make sure you have sufficient insulation in the roof to prevent freezing at the roof surface under a deep snow pack
  • Proper ventilation under the roofing material that carries heat escaping from the building elsewhere and assures a cold roof surface is needed. The attic/roof temperature can be controlled by installing sufficient insulation and providing natural or mechanical ventilation. The roof temperature should be similar to the outdoor temperature.
  • Ensure insulation is not right against roof sheathing.
  • Install heat tape or cables that create channels for meltwater to escape through an ice dam at your eavestroughs.
  • You can manually remove ice dams from roofs, but make sure you don’t poke holes in the roof. Or call a roofing professional who has the proper equipment to do this.
  • Clean eavestroughs out in the fall to allow melting water to escape.


Homeowners should check their properties for warning signs of ice dams; icicles along edges of eavestroughs and frost accumulation in your attic. If you see these signs, contact a roofing professional as soon as possible to help rectify the problem before it causes damage and a potential insurance claim. We are all stronger when we work together preventing claims.


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