Real estate

Ice dams and the truth about gutters, metal roofs

Sean Proctor/Globe Staff

Q. I recently noticed a house that had the gutters at least 6 inches below the roof edge. Would putting on wider facia boards and dropping or even removing the gutters on my home help me avoid a repeat of the $10,000 repair I incurred last year because of ice dams? These would be relatively cheap fixes in comparison. Your thoughts?

K. DEPPERMAN

A. People who tell you gutters cause ice dams don’t know the science behind ice dams.

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In order to separate fact from fiction and to make the right decisions for your home, here’s what you need to know: Ice dams result from your roof heating up to a temperature greater than 32 degrees. That is the MAJOR reason, and snow is the key ingredient in the ice dam recipe. As the snow melts and runs down your roof, it can freeze when it hits your soffit/overhang area. Overhangs do not get warm like the upper roof does. The snowmelt freezes on the overhang, creating an ice dam, and then the melted water backs up into the warmer roof area, doesn’t freeze, and seeps into your home.

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And this is where the confusion about gutters begins. In my experience, gutters can result in larger, thicker ice dams by creating a shelf and more depth to the overhang. The more feet of overhang on your roof, the greater the potential for bigger ice dams forming. Either way, with or without gutters, you will have ice dams, so don’t go tearing the gutters off your house or, for that matter, lowering them. Your best bet is to improve the insulation, sealing, and ventilation in your home to prevent heat loss to your roof.

Q. Your opinion, please, on metal roofs. Do you recommend them? After the winter we had last year, I expected to see more of them going up. Wouldn’t it solve the ice dam problem? Thanks.

REDSOXFAN555

A. How ’bout them Sox? Sigh. Metal roofing can help but is not an ice dam panacea. A metal roof will generally shed snow better, but snow running down the roof will still freeze on the unheated overhangs, creating an ice dam. Metal roofing can be just as susceptible to this as any other roof.

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Ice dams are not a roof-material problem, really, but a heat loss and insulation issue. Proper ventilation will help mitigate the heat loss but will not cure what is the substantive source of the problem. Air-sealing and insulation combined with the proper attic ventilation will.

Rob Robillard is a general contractor, carpenter, editor of AConcordCarpenter.com, and principal
of a carpentry and renovation business. Send your questions to homerepair@globe.com or tweet them to @globeaddress or to @robertrobillard.