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How to Prevent Ice Dams from Forming on Your Roof


With the arrival of winter, property owners should anticipate possible roofing problems. A common one is the formation of ice dams. Although ice dams start on the roof, they can migrate and create problems inside your home.

How Ice Dams Form

Ice dams form when snow that has melted on the upper, warmer part of the roof refreezes into a band of ice near the colder edges. Once the dam forms, melting snow backs up behind it and this water may begin to seep under the shingles. This seepage can run back five, even 10 feet under the shingles. Before long, it damages the soffits, walls and ceilings of your property.

How to Prevent Ice Dams

Since it is temperature variances on the roof that make ice dams possible, keeping the roof cold is one way to prevent ice dams. Since the attic is above the dwelling areas that have the warmer temperatures, the attic is often the first place to start when trying to balance the roof’s temperatures. To prevent ice dams, you should:

Insulate the attic. Ideally you should use ceiling insulation rated at R-38 or above. However, if space restrictions make this impossible, then using a high R/inch insulating foam (R-6/inch) is a decent alternative. Once installed, seal the insulation.

Use a ventilation system. Ventilation systems that run from the soffit to the ridge of the roof are very effective. These vents should run uninterrupted over the length of the house or building. Ridge vents create exhaust pressure that sucks cold air into the attic through the soffit vents. Note that installers must put in insulation baffles above the exterior wall to protect the insulation from the air coming in through the soffit vents.

Seal sources of air leaks. Holes and cutouts through which wires, plumbing fixtures, lights, bathroom exhaust fans, chimneys and hatches for attics protrude let air leak. The use of caulk, weatherstripping, packed cellulose or urethane spray foam insulation will seal these air leaks.

What to Do After It Snows

If the roof is flat or moderately pitched, it’s probably safe to stand on the ground or on a ladder to use a roof rake to remove snow from the edge of the roof. Just don’t rake too aggressively or you could knock off some of the protective granules on asphalt shingles. If an ice dam has formed, place a stocking filled with calcium chloride ice melter across it horizontally. Do not use rock salt as it may damage the roof.

Of course, safety is always an issue. If you cannot safely access any area using a ladder and other tools, call a contractor. At L&L Contractors, we only do high-quality work with a trained and knowledgeable staff. No matter how big or small the job, you can count on us to do it right. Contact us today for more information on how we can help you out this winter and all year round.

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