Heavy snow on roof can lead to costly ice dams

Talk about it

GRAND FORKS — Pleased, are you, with that deep, cottony snow curling over the eaves of your home and making your roof look like one of those fairytale thatched jobs in the enchanted forest?

Yes, it’s pretty. But gnomes, ice gnomes, may be at work.

Ice dams, that is.

The problem is more severe and widespread in areas that traditionally get more snow and winter temperatures fluctuate more around the freezing mark, 32 degrees Fahrenheit.

This region can go through many winters when houses have little or no snow accumulating on rooftops.

Not so, this year.

Ice dams form when rising heat from inside the home pushes the roof surface temperature above 32 degrees, melting snow that runs down the roof until it collects on the colder (below freezing) overhang and gutters and becomes impermeable ice.

That ice dam grows and eventually may block new melt water and force it back up the roof, under shingles and through the roof, damaging ceilings and walls inside.

“You have heat loss from the home, the snow acts as an insulator and melting collects in the gutter at the bottom of the eave edge,” said Jeff Skinner, of Skinner Roofing in Grand Forks.

“Then it freezes up, and when we get more melting the water runs down but can’t get off the roof because it’s dammed up. It goes back up until it gets above the overhang, and that’s when the problems start.”

Blizzard Alvin delivered more than two feet of snow last week, and “there wasn’t a lot of wind the first 24 hours, so it accumulated,” Skinner said.

It may be too late in some cases, but homeowners could take precautions to avoid more serious problems in late February and March, when, chances are, the region will have some sunny 40-degree days that increase roof runoff but have little effect on established ice dams.

“Get the snow off the bottom of the roof,” Skinner said. “That’s where it starts. If you get that off now, it may minimize the damage.”

It isn’t an easy task, and it can be dangerous, especially if you attack the rooftop drifts from above. Various retail outlets sell extendable snow rakes.

Another precaution, outfitting gutters with heat cables, can prevent the formation of dams, “but you’re talking serious money there,” he said.

He agreed that ice dam problems are more likely to occur in older homes.

Many homes built in recent years may have an ice and water shield that prevents water from working into wood decking or through nail holes beneath the shingles, he said, though the cost — a few hundred dollars — could sway some builders.

Don’t wait, though, the experts say, until glaciers form on your eaves, small lakes take shape and your Sheetrock turns mushy enough to write notes in with a finger.

“It’s too late then,” Skinner said. “You just don’t go out and chip ice out of the gutter. You’re at the mercy of the melt then.

“It’s hard for people to believe that the water migrates up the roof and under the shingles, but it does,” he said. “With the ice dam, the water has nowhere else to go.”

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The Grand Forks Herald and the Echo Press are both owned by Forum Communications Company.

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