Ice dams are a hassle for your roof and your siding
Prevent pesky ice dams InterNACHI

Icicles hanging from the edge of a roof can be really pretty, but they can also be symptomatic of a problem affecting many homeowners this winter - ice dams. Most easily described as a build-up of ice around the edge of your roof, ice dams can quickly damage the shingles and cause water to leak into your attic. Not only will the leakage cause costly damage to the internal structure and material of your attic, but it’ll decrease the insulating capacity of your attic insulation and create a breeding ground for mold and mildew. Not to mention the potential to tear gutters away from the house and even cause the roof to sag or worse, collapse! To avoid having to call a professional roofer in the middle of winter, it’s important to know what ice dams are, how to prevent them, and what to do if you’re noticing them around your roof right now.

Where Do They Come From?

The process of how ice dams form in your gutter
Ice dams This Old House

Ice dams are caused by a difference in temperature between the middle of your roof and the edge. Snow lands on the middle of the roof, which is warmer due to heat in the attic caused by poor insulation or insufficient ventilation/circulation of air. Warmer temperatures cause the snow to melt and run down to the cooler edge of the roof, where it then freezes. This happens over and over again, causing a buildup of ice that prevents snow (melted or not) from reaching and escaping over the edge. Ice dams can grow large enough to push shingles off of the roof, and the backup of water can leak into the attic, damaging the structure, the insulation, and anything else you might be storing. Once ice dams have started to form, a heavy snowfall can actually make them worse - snow is ironically a good insulator, and a heavy snowfall can insulate the roof from the cooler air and actually help it heat up faster, causing more snow to melt and refreeze along the edge.

How do I Prevent Them from Forming?

Stop ice dams from forming in your gutters
Gutter prevention Gutter Helmet

There are a few measures to take that can prevent ice dams from forming around your house.

  • Insulate your attic floor: Especially in older homes, the insulation is often below-grade and not enough to keep the heat inside where it belongs. But if you can minimize the heat escaping to the roof, you can keep the temperature down and prevent snow from melting and refreezing.
  • Update attic ventilation: Your attic can have three different types of vents (soffit, ridge, or gable) and attics usually use a combination of the three, along with an attic fan or two. You might need to consider having a professional install more vents and/or fans to have the right amount of ventilation for your attic size and shape. Ventilation and circulation work in conjunction with insulation to keep the attic cool and moisture-free.
  • Seal the attic: Not only should the attic be sealed from the outdoors, but you should make sure anything that goes into the attic from the floors below - exhaust pipes, cables, HVAC ducts, a chimney - are sealed, caulked, or covered with the appropriate material. This can prevent heat from below escaping into the attic, which will also keep your heating bill lower throughout the season.

...and If I’m Too Late?

A roof rake can help clear those gutters
Roofing methods Wonder How To

Don’t worry: there are also some things you can do to stop ice dams in their tracks. If you’ve already got snow on the roof, you’ve started to notice the dams forming, or you’ve found a leak in the attic, using some of these stopgap measures can save you a lot of money in the long run.

  • Use a roof rake: A roof rake allows you to pull snow off of your roof from the safety of the ground. Try to use one especially after a heavy snowfall, or if temperatures are bouncing above and below freezing.
  • Install heating cables: One temporary solution is to use heating cables, which keeps the edge of the roof just as warm as the middle.
  • Blow cold air into the attic: Not the most energy efficient, but using a box fan to cool down the attic will also cool the temperature of the roof, leading to smaller or nonexistent ice dams and no damage to speak of.
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