Besides numb fingers, slippery roads, and school closings, ice dams are another winter plague in Minnesota. These frozen formations can be very destructive to the exterior and interior of your home. With proper precautions they can be avoided, but if they do manage to damage your home, cleanup and remediation should be undertaken immediately.
How are ice dams formed?
Ice dams are a product of an insufficiently insulated and/or improperly vented attic combined with below-freezing outdoor temperatures and of course, snow. As heated air from the living space rises and enters the attic, the roof warms. The warmed roof causes the snow on top to melt and trickle down to the roof edge, which is colder. There, under colder conditions, the water freezes. As this process continues, the water flowing down the roof refreezes and adds to that at the edge, causing a ridge, behind which water backs up—thus, an "ice dam."
What kind of damage do ice dams cause?
As more water melts, runs down the roof, and freezes, the ice dam grows in size and thus can become quite heavy. This weight causes great strain on the gutters and downspouts, potentially detaching them from the house. Additionally, as water backs up behind the dam, it is often forced under the shingles, where it pools. When this water again freezes (with a drop in outdoor temperature) it will expand under the shingle and cause damage. If it does not freeze, however, it may well leak through the roof.
And this is where the potential damage is greatest—inside your home. As water backs up behind the dam and spreads out over the roof, it can eventually seep through the roof or find its way in through holes or fissures, making its way into the attic. There, it drips into the insulation, potentially saturating it and establishing a breeding ground for mold. It further seeps through the floor of the attic to your ceiling, causing water spots and water damage to the bedroom ceilings and walls. This is often the first sign a homeowner has of a problem with ice dams (besides perhaps icicles hanging from the edge of the roof). In particularly bad cases, homeowners have witnessed their ceilings "raining."
How can ice dams be prevented?
Since the main contributor to ice dam formation is heat loss into the attic and a (relatively) warm roof, the preventive solution is to sufficiently and properly insulate your attic floor to prevent warm air from the living space penetrating it. A further contributor is referred to as bypass, or air leakage, which occurs via the gaps or holes surrounding light fixtures, wires, or flues into the attic from the living space. These need to be properly sealed to cut off the flow of warm air from below. Further, proper ventilation is critical to the prevention of hot air being trapped in the attic. A combination of ridge vents and soffit vents is most recommended. And remember: dryer vent lines or bathroom vents should NEVER exhaust into the attic but should always end outside.
On the border of prevention and treatment is the installation of heated cables. These cables, warmed by electricity, run along the eaves and in the gutters and can ameliorate ice buildup as well; however, these are more of a band-aid than a preventive measure.
If preventive measures are not undertaken (or have failed) and an ice dam forms, there are a few DIY methods that have been suggested to tackle them, including using a wheeled roof-rake to remove snow from the roof, the application of chemical de-icers, the spraying of warm water from a pressure-washer, and attacking it with a hammer and chisel (yikes!). Another option is to hire a professional ice-dam removal company to apply steam to melt the ice dams, allowing the backed-up water to flow safely off the roof through the gutter system. Again, these are all options once a dam has formed. After successful removal the cause should be pinpointed and remedied.
How is the water damage from ice dams mitigated?
In the unfortunate event that water does infiltrate your roof and enter your attic, prompt discovery and mitigation is key to minimizing damage to your home and preventing mold growth. The first step would be to have the affected insulation removed and the area thoroughly dried. New, dry insulation would then be installed, in the appropriate amount (remember, inadequate insulation can be a main contributing factor to the formation of ice dams in the first place). An insulation company can also ensure that any bypass areas are appropriately sealed.
If water has leaked through the attic floor to bedroom ceilings and walls, demolition of some affected areas, such as drywall and flooring, may be necessary. A water damage specialist can help you determine what is salvageable. Once the necessary areas have been demo'd, the remaining affected areas are thoroughly cleaned and sanitized to avoid contamination and prevent mold growth. Thorough drying procedures are then followed, utilizing air scrubbers, dehumidifiers, and air movers, with lay-flat ducting to direct air to where it's needed in order to accelerate the process.
Once this has been accomplished, any rebuilding of demo'd areas will take place, and with that a return to normalcy—hopefully, with all necessary steps having been taken to eliminate the factors that led to the ice-dam formation and to prevent its recurrence.
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Many thanks to our water-damage specialist Zach C for lending his expertise to this article.