Icicles, ice dams, and your roof

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Icicles, Ice Dams, and Your Roof

While icicles hanging off the side of a roof can look pretty and festive, they can actually cause trouble for your home. Icicles are often a sign of an ice dam on your roof, and ice dams can cause significant damage to shingles, insulation, interior walls, and personal property. In extreme cases the structural integrity of your home may be compromised!

What is an ice dam?

Ice dams are large masses of ice that collect on the lower edge of a roof or in the gutters. Signs that ice damming may be occurring:

  • Snow is melting but there’s a line of ice or snow at the eaves that is not draining.
  • Formation of large icicles from the eaves.
  • Water dripping out of the soffit or gutter.
  • Shingles appear worn or faded on overhangs.
  • Shingles have rolling humps or dips on eave line.
  • Interior walls or ceilings have visible water damage under eaves.

While icicles hanging from a roof’s edge may be a warning sign, ice dams can form without the presence of any large icicles.

What causes an ice dam?

Ice damming usually occurs when there is a significant amount of snow on the roof. If the temperature in the attic is above freezing, it warms the roof sheathing, which melts the snow lying on the shingles. The melted water then flows down to another part of the roof that is cooler – usually the overhang and eaves, and the water freezes. The ice forms a small dam that builds up slowly as more and more melt water refreezes. Eventually, water backs up behind the dam and works its way up under the shingles until it begins to leak through the roof, and into the living space below.

The problem can get worse as the backlog of slush and snow created by the damming forces the shingles up, dislodging nails in the process. Nail holes and small cracks are perfect pathways for flowing water. These pathways can make their way into your attic, seeping through your insulation and migrating into your walls and through your ceiling. The end result is damage to the interior of your home and personal property. If the leak is not obvious, it may be years before you notice mould or wood rot.

If you suspect you have an ice dam

If you’re concerned an ice dam is already forming on your roof, it’s best to remove snow from a heavy snowfall immediately to help prevent ongoing build-up.

A roof rake or push broom with stiff bristles can be used to help remove snow off flat and low-slope roofs, as you can remain on the ground to remove snow. You can also contact a professional to do the job.

How to help prevent ice dam formations in the future

Here are a few ways to prevent, or at least minimize the risk, of ice damming next year:

  • Keep gutters and downspouts clear of leaves and debris
  • Identify areas of heat loss in your attic and properly insulate those areas, including wrapping and insulating heating duct work
  • Check your exhausts. Make sure all ducts from bathrooms, kitchens or other areas exhaust outside of your home, not to the attic
  • Ensure the attic has proper, continuous ventilation under the roof deck (the colder the attic, the less melting and refreezing on your roof)
  • Have your chimney flashing and roof inspected by a professional and repair or replace it if necessary.

Do you have questions about your roof? Let us know in the comments below.