My parents hired me again, this time to shovel snow. Massachusetts has seen over 5 feet of snow this February, and the extra weight on roofs threatens to collapse them. Modern roofs in coastal New England are designed for a snow load of 30-50 pounds per square foot, which corresponds to 2-3 feet of moderately dense snow (the kind New Englanders are used to) or 7-10 inches of ice. But older roofs may have been built to lower standards, and poorly designed roofs may allow dangerous ice dams to grow.
Ice dams form when snow melts on a warm roof, runs down, and refreezes at the overhang. You can prevent them by insulating your attic well and ventilating it properly, with soffit vents and ridge vents. The resulting airflow keeps the same temperature above and below the roof, so fallen snow stays snow. If your house is prone to ice dams, you should rake the snow off your roof immediately so it never has a chance to melt.
Once you’re cursed with an ice dam, you can still try to get rid of it, and that’s one thing I tried to do for my parents. The best method for ice dam removal is a steamer, which blows hot moist air and melts ice quickly and harmlessly. If hiring a steamer is beyond your means (note to anyone with a steamer and builder’s insurance: you can make a killing in New England!), an alternative is using a sock full of salt to melt the ice, but that can corrode the roof.
I followed the lead of some contractors in town and used a hammer and chisel to chop out the ice, but abandoned the idea when I saw the risk of physically damaging the roof. After that, it was back to raking. If I can’t clear the ice dams, at least I can eliminate their source so they don’t get any bigger. For my final chore, I investigated inside the attic and confirmed that the roof rafters remain structurally sound, with no cracks or sagging. My parents will rest a little easier now.
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