Common Gutter Problems Part 4: A Word About Ice Dams

Those winter icicles hanging from the front of your gutters may be picturesque. But they point to a potentially serious problem called ice damming.

Ice dams are not a problem with your gutters, per se, although your gutters are part of the process. Here’s how it works and why you need to deal with it.

Snow on your roof can melt from underneath because your roof is warmer than the ambient air temperature. For one thing, most roofs are dark in color, and dark colors absorb more heat from the sun than do light colors. For another, hot air from your interior living spaces will migrate to the roof if your attic is inadequately insulated or ventilated.

When snow melts from underneath, the water drains away under the snow and flows into your gutters. But your gutters, which hang out past the roof eaves, are cold. When the snowmelt hits your gutters it refreezes. In time the frozen water builds up and creates an ice dam, which in turn causes more water to back up and refreeze. Left to itself, the accumulation of ice will work its way into your roof shingles, under the tar paper, and eventually into the plywood beneath.

The problem of ice damming, then, is addressed not by repairing or replacing your gutters, but by checking your attic insulation and ventilation. The trick is to ensure the attic and roof is about the same temperature as the outdoor air. After that, you can hire a roofing contractor to install an “ice shield,” or roll of special insulation, under the shingles and along the bottom 24 to 36 inches of the roof.

Nevertheless, good gutter maintenance plays a part in preventing ice damming. Cleaning your gutters should be done yearly before winter. If your gutters are clear and unclogged, water from snowmelt is more likely to drain away rather than refreeze and back up. Also, some gutter companies can install a heating cable to run through the gutter trough and along the roof edge.

While you’re at it, think about installing snow guards along the edge of your roof. When snow and ice melt from underneath, the entire mass can break away and slide all at once off the roof. And when that happens, the avalanche of snow and ice can take your gutters with it. Snow guards ensure the mass is broken up rather than sliding off in a single piece.