Ice dams: How to prevent them . . .

Home Work

January 20, 1996|By Karol V. Menzie and Randy Johnson

It was a cozy winter evening, just a group of quilters sitting around discussing ice damming.

All of a sudden, everybody has it. People whose roofs have been sound for decades are now looking at major leaks.

Ice damming, a buildup of ice along the edge of a roof, occurs during winter freeze and thaw cycles when heat seeping through the roof causes snow to melt at the surface. The water runs under the snow to the roof's edge, where it meets the cold eaves and freezes.

Cycles of freezing and thawing cause an ice ridge to build up, and the ridge keeps water from dripping off the ends of the roof. The trapped water pools and backs up under the shingles, where it can leak into the house. Ice dams also can occur around skylights, because heat loss around them tends to be even greater than from other parts of the roof.

Leaks can occur on interior walls, between window frames and walls, or where structures meet, such as where a porch adjoins the house.

A temporary solution is to get up on the roof and chip a channel through the ice so water has a way to escape. If the problem is occurring at a skylight, a single channel may solve it.

However, walking on a snow- and ice-covered roof, or even in climbing to the top of a ladder anchored in snow or ice on the ground, involve some real safety concerns. Unless you have a serious leak, the quick solution is probably more hazardous than the problem.

The best way to deal with ice damming is to prevent it. There are a couple of products on the market that alleviate ice damming. One system uses heated coils zigzagged along the roof edge. When they're on, they keep ice from forming and allow runoff water to keep moving. Prices are fairly reasonable -- $44 for a kit with 24 feet of coil for one brand, said Bill Dorman, president of People's Electric in Baltimore. But the product may have to be ordered from an electrical supplier.

Another system -- which has to be applied to a roof that's bare of shingles or other covering -- is a shield layer. It's a self-adhering membrane, perhaps made of rubberized asphalt, that's about 3 feet deep. It protects the edges of the roof and prevents water from working its way under the shingles and back into the house.

Ice damming is not usually a problem in the mid-Atlantic region, or in any area where the snowfalls tend to be lighter and to

melt quickly and disappear.

If you're having a problem this year after the heavy snows, you'll have to decide if it's just a fluke, or if it seems serious enough to warrant installing heating coils or a new roof edge.

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If you have questions, tips or experiences to share about working on houses, write to us c/o HOME WORK, The Sun, 501 N. Calvert St. Baltimore, 21278.

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