Wintertime icicles may look charming, but they usually signal a serious — and potentially costly — problem. Often lurking behind that thick ridge of ice on your roof is a pool of melted water, hence the term ice dam. That accumulated water can work its way under roof shingles and into the home, causing significant damage to ceilings, walls, and floors.
Additionally, the sheer weight of the ice dam often causes gutters and downspouts to pull away from the house, sometimes bringing the fascia boards with them. Preventing ice dams helps avoid damage and costly repairs.
The Damage Ice Dams Can Do
Over the five-year period leading up to 2007, water damage and freezing accounted for the second largest share of homeowner insurance claims, according to Claire Wilkinson of the Insurance Information Institute. The average homeowner claim for such damages was $5,531.
Ice dams are responsible for cracked plaster ceilings and walls, peeling paint, soaked carpets, and buckled wood floors. Less visible but no less destructive effects include drenched insulation, rotting joists, and the formation of mold. The most common form of ice dam damage is collapsed rain gutters, which can cost $100 to $300 per side to repair.
What Causes Ice Dams
As heat rises from a home, it melts the accumulated snow on the roof. That melted snow travels down the roof in liquid form until it reaches the eave line and gutter, where it refreezes due to colder temps. This ice ridge continues to expand, blocking the flow of subsequent snow melt.
As water continues to melt higher up the roof, it collects behind the ice dam in the form of a puddle. Because that water sits over the warmer portion of the roof, it doesn’t freeze.
In order for ice dams to form, there needs to be roof snow buildup, home heat loss, and subfreezing temperatures. The more snow, the larger the heat loss, and the longer the subfreezing temperatures remain, the higher the likelihood that ice dams will materialize.
How to Prevent Ice Dams
Homeowners can’t control the weather, but they can do something about heat loss. “The main goal is to keep heat from reaching the roof, thus preventing snow melt in the first place,” explains Doug Bruell, president of Cleveland’s 25-year-old North Coast Insulation. Proper insulation and ventilation of the attic space is intended to keep the roof surface at or near outdoor temperatures.
Typical steps include insulating the attic floor and installing soffit, gable and/or ridge vents to expel heat. Folding attic stairways and recessed light fixtures also need to be insulated. “All penetrations into the attic from the heated living space need to be addressed,” adds Bruell. Homeowners can expect to pay $800 to $1,500 to insulate the attic, plus another $300 to $600 for the installation of vents.
The process is a bit more involved for homes with finished attics, says Bruell. To facilitate sufficient cold air flow from soffit vent to ridge vent, baffles or tubes are installed between the ceiling insulation and the underside of the roof. This might involve opening up the ceiling.
Tip: You’ll save money with insulation. According to the U.S. Department of Energy, adding insulation to an unheated attic will have a greater impact on energy consumption than placing it anywhere else in the house. A properly insulated and ventilated attic not only reduces winter heating bills, it will trim summer cooling bills by expelling heat buildup. Proper attic insulation can save you 10% to 50% on your heating and cooling bills.
In theory, roof rakes, brooms, and other long-handled devices can be used to remove snow before it has a chance to melt. In practice, however, the scheme is difficult to pull off, considering that most homeowners can’t reach all areas of the roof.
Electrically-heated deicing cables, which install along eave lines to inhibit water freeze, are only moderately effective, says Bruell. “These heat cables often just back up the problem, forcing the dams to form higher up the roof.” In addition to the purchase price ($150 to $300), and installation ($300 to $500), these cables require electricity to run. They also can shorten the life of roof shingles.
How to Remove Ice Dams
Homeowners suffering the effects of an ice dam — or those who fear a leak is imminent — can hire a roofing company to remove the ice buildup. Rather than employ hammers, chisels, and salt, which can damage the roof and gutters, technicians will steam away the ice and remove any remaining snow. Expect to pay around $500 or more for the service. It goes without saying that do-it-yourself removal can be dangerous when it involves ladders, heavy ice, and slippery roofs.