For homeowners living in cold, snowy regions, roof ice dams are a brutal fact of life, making ice dam protection an option to consider when roofing your house. The importance of this issue is even greater because ice dam protection materials are typically offered by roofing companies in cold climates. It is natural and prudent to be wary of add-ons offered by companies soliciting your business. What is ice dam protection and is it a wise choice?
How Ice Dams Form on Your Roof
Before looking at ice dam protection, it is instructive to witness the entire lifecycle of an ice dam. Ice dams are not an aberration or a statistical freak of nature. Instead, with a certain set of conditions, ice dams are quite likely to form on your roof.
- Snow, ice, or hail gather on your house's roof. As long as the ambient temperature and the roof temperature are below freezing, the accumulated materials remain frozen.
- The frozen materials begin to melt, either due to exposure from the sun, increased ambient temperature, or heat rising from the house. Homes with poor attic insulation are more susceptible to ice dams because more heat escapes through the roof.
- The melting materials drain downward, toward the eaves, gutters, and eventually the ground. If the eaves remain above freezing and the gutters carry away the water, ice dams will not form.
- Often, the temperature drops again (or never rises high enough) so that the eaves stay below freezing while the upper area of the roof is above freezing. Eaves and gutters hang off to the side of the roof, so they do not benefit from heat rising from the house's attic.
- Melting snow or ice blocks up in the gutters, either from debris or ice. With this, the ice dam has begun to form.
- The ice dam increases in height.
- More frozen materials melt from above, drain to the ice dam, and quickly freeze.
- Eventually, the cycle reaches a point where there is a solid wall of ice in the gutters. Water gathers above that point and remains for hours and even days until the ice dam melts and releases the water.
How Ice Dams Can Ruin Your House
The effect of ice dams is often not experienced until much later. Weeks or months later, perhaps in a warm season, you may begin to notice mold spots forming on your ceiling. Or you may see large, dark-rimmed water spots on your ceiling. If you go into the attic, you may smell mold and mildew. Attic insulation might be damp or moldy.
Typically, these problem areas will be confined to the perimeter of your house. A water spot on the ceiling usually will be located within 6 feet of an exterior wall.
When the water melted behind the ice dam, that backed-up water had the luxury of time to seep under the shingles. After the water seeps between the shingles, it flows into the attic, permeates through insulation, and soaks ceiling drywall and joists. The problem is exacerbated if you have wood shake shingles, which do not hold back water as well as asphalt or composite shingles.
Why You Should Install Ice Dam Protection
When roofing companies install ice dam protection, they run a strip of a rubber-type flashing all around the perimeter of the roof before laying down the shingles. This flashing material is made of high-density cross-laminated polyethylene that measures 36 inches wide and about 75 feet long. The width extends from the edge of the roof upward toward the ridge. The length is usually long enough to cover most houses without seaming.
Ice dam protection does not prevent the ice dam. Instead, it helps to limit or prevent the seepage from the ice dams that moves under your shingles from reaching and damaging the wood deck below the shingles. To prevent ice dams, install roof heat cable.
Ice dam protection is recommended in climates with freeze-thaw cycles. The materials must be added at the time of roofing; they cannot be added retroactively.
Ice dam protection materials run between $150 to $250 for 75 linear feet. Two rolls would cover a small home. If you feel that the roofing company is quoting an especially high price for the materials alone, you can easily price-check them at most home centers. Keep in mind, that is for materials only, not including labor or a price markup set by the roofing company.