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Ice Dams: Coming this winter to a roof near you

As surely as winter follows fall, there are going to be ice dams on Canadian roofs this winter, backing water under shingles, allowing it to drip through ceilings, and breaking the hearts of homeowners across the country.


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August 31, 2015 by John Bleasby

When is the best time to resolve an ice dam issue? Not in January or February, when temperatures are below freezing, the wind is howling, and the snow is falling. No, the time to deal with an ice dam is when the weather is still warm. If you’re finishing up a renovation on a customer’s home, now is a good time to check out their attic space and determine if there’s a problem in the making.

Nothing forces water uphill better than an ice dam
Even new technology in the shingle industry will not solve the ice damming problem on its own. According to professional roofer Brian Audia of A&G Roofing, ice dams are the result of poor design as much as anything else. Yes, homeowners can install electric heat cables in a zig-zag pattern a few feet above the eaves and through downspouts, but it’s a Band-Aid solution to a larger issue.

Ask roof experts like Audia and they’ll tell you that the root cause of ice dams is poor insulation and/or ventilation inside the attic space. As he puts it “You either design correct insulation and ventilation in the attic or you manage the problem from the surface. Ice damming is not a failure of product or workmanship. It’s a failure of planning.”

The ice dam cometh

Anatomy of an ice dam. One picture says a thousand words

Anatomy of an ice dam. One picture says a thousand words

Audia sees dozens of ice-damming problems each year on homes, condominiums and commercial rooftops alike, particularly on additions or renovations to older buildings. In addition to recommending properly maintained insulation, he adheres to the very critical 300:1 ratio of ventilated attic space to roof area. Without balanced air movement inside the attic and soffits, the roof deck itself can suffer premature deterioration from the underside, plus heat loss and ice damming in winter. Damage to interiors can be extensive.  Damage to roofs can even occur in summer; a super-heated attic can cook and break down an asphalt shingle from the underside.

No shingle, tile or sheet is immune
Audia says that ice damming can occur with tiles or shingles of any type, even steel sheeting. In fact, although steel roofing sheds snow and water faster than shingles, and may escape some of the pitfalls of poor attic ventilation, the sheets don’t seal to themselves nor have profiles high enough to prevent ice backup. Buttal tape or silicon on seams can help but are not sure bets. Furthermore, various ice and water shield products applied underneath roof materials do not offer any specific guarantees for longevity. While certainly useful, as far as Audia is concerned they are no substitute for a well-planned roof system that starts under the roof itself.

Taking the initiative and inspecting the attic space now while you are still on site will serve your customers well, and potentially save them heartache this winter.

Read Canadian Contractor’s feature on roofing from the May/June print edition
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1 Comment » for Ice Dams: Coming this winter to a roof near you
  1. Reg russell says:

    I have a 8 /12 pitch with a product called Ondura corrugated asphalt sheets. We have no problem with ice dams as the snow is gone within two days. We have ice and water shield for the first three feet and each sheet is 72 inches to the weather and a six inch overlap. Check it out on the web.