The Problem With Ice Dams

I recently received a call from a friend of mine telling me that he had a water leak underneath his toilet. The water was leaking along the water pipe the supplied water to the toilet and around the sub floor. So right away we assumed the the pipe was leaking inside the wall. The first thing we did we removed the toilet and cut a hole in the drywall around where the pipe came out. We soon found out that the pipe was not leaking at all but that the ice dam that had formed in the corner of his house was leaking in through the wall. After taking care of the ice dam we fixed all the rotted wood and drywall that was ruined from water damage. All this could have been avoided with a few precautionary measures.

Here are a few steps to avoid ice dams.

Close up attic bypasses
In the average home, about one-third of the heat loss is through the ceiling into the attic. And most of that loss comes from air leaks caused by unblocked walls, gaps in drywall, and cracks around light fixtures, plumbing pipes, chimneys, access hatches and other ceiling penetrations. Air leaks can be tough to stop. You have to climb into your attic, pull or rake back insulation, and plug the leaks using foam, caulk and other methods. Low roof angles make some air leaks difficult to reach. This work is definitely a cool weather project; your attic will be unbearably hot otherwise. Always wear a dust mask, a long-sleeved shirt and long pants to help prevent skin irritations caused by insulation.

Measure your attic insulation level
While you’re in the attic, check the depth of your attic insulation. Building codes require about 12 to 14 in. of fiberglass or cellulose. Add more if you have less than 8 in. and have had ice dam problems in the past. Blown-in cellulose and fiberglass are usually better than hand-placed batts, because they fill more tightly around rafters, joists and other obstructions, leaving fewer gaps. It’s usually worth hiring a professional for this job; you probably won’t save much by doing it yourself. However, if you can’t find a good price, you can rent a blowing machine from a rental yard or home center. Often, the use of the machine is free with the purchase of insulation. (Look under “Insulation” in your Yellow Pages.)

Add roof and soffit vents
Attic ventilation draws in cold outdoor air and flushes out warmer attic air, cooling the attic and the roof in the process. The minimum ventilation area (size of the openings) should be about 1 sq. ft. of vent per 300 sq. ft. of ceiling area (attic floor area), when half the vent area is low on the roof and half is high. Actually figuring all this out is a bit complex; you’d have to examine your existing vents to find the area of each, which isstamped on them. As a rule of thumb, put an 8 x 16-in. vent in the underside of the overhang (soffit) in every other rafter space. (If you’re planning to rebuild the soffit, install a continuous 2-1/2 in. wide “strip” vent, because it will look better.) And install a continuous ridge vent along the peak. If the ridge on your roof is much shorter than the roof edge-on pyramid-shaped roofs, for example-add the common squareshaped roof vents near the peak. Add enough so their ventilating area is about equal to the area of soffit vents. This might deliver a whole lot more ventilation than the minimum requirement, but don’t worry. You’re unlikely to have too much ventilation.

Rake the snow off your roof after a heavy snowfall.
A $30 snow rake, which is an aluminum scraper mounted at a right angle on a telescoping aluminum pole, is the simplest solution for occasional heavy snows. If you pull the snow down, it can’t melt and form an ice dam. It’s an effective, if tedious, solution, but only for single-story homes. You can’t reach the second-floor roof. (Never use a snow rake when standing on a ladder!) And you have to take care not to break the shingles, which are brittle in cold weather. Most home centers and hardware stores in ice dam country carry, or can order, snow rakes. Get one before the snow comes; demand goes up after the first heavy snowfall of the season.<