Snow and ice are part of winter life in cold climates. If you haven't taken the right precautions, however, they can do serious damage to your roof. The formation of ice dams on your roof can lead to wet insulation, stained interior ceilings and walls and costly repairs. Ice dam damage may result in mold and mildew problems that are difficult to treat.
Cycles of thawing and refreezing snow lead to the buildup of ice along your roof's edge. Escaping heat from your roof deck melts accumulated snow. The water from the melted snow makes its way down your roof and toward the cooler edges, where it refreezes into a layer of ice. The process is repeated as new snow melts and flows down the roof only to refreeze again. Slowly the ice builds up along the edge, forming an ice dam.
Once formed, an ice dam works like any other dam. It stops the flow of water, causing it to pool and find a different route. The dammed water backs up under shingles, then finding ways into the house and soaking insulation, damaging sheetrock and staining ceilings and walls. The moisture in all the layers of the house can lead to dangerous mold and mildew. Exterior paint and siding can also bubble and deteriorate from the water and ice.
The best way to fight ice dams is to prevent them from happening in the first place. Proper insulation is the best way to keep your roof cool and keep the snow that lands there from melting. Good insulation will keep the heat in your house and away from the attic space and roof. Make sure that your insulation has an R-value of 38 or above.
Be sure you don't have any air leaks. Check all areas around chimneys, vents, plumbing and wiring. Leaky ductwork can allow warm air escape toward the roof.
Kitchen and bathroom exhausts that terminate above the roof can also cause snow to melt. These may have to be rerouted or insulated.
Proper attic ventilation can help keep your roof deck cool. Heat in attic spaces rises. If the warm air has nowhere to go, it stays in the attic and heats the roof. Having small ridge vents allows the warm air to escape and cool air to replace it. This lowers the attic temperature and keeps the roof deck above cool too.
You can also add electric heat cable systems to areas where ice dams usually form. If you are reroofing, before applying the shingles, install a flexible, self-adhesive, rubberized waterproofing membrane in the ice dam prone areas to prevent leaks.
If you already have an ice dam, there are few things you can do to minimize the damage.
Remove the snow from the roof. Be very careful doing this. It's not just dangerous for you, but for your roof too. Roof rakes and push brooms can easily cause damage to the shingles.
If water is already leaking into your home, make a channel in the dam. Use warm water to melt away part of the dam so that the pooled water can flow off your house. You will have to repeat this frequently since new ice will quickly form.
Taking the proper preventative measures to stop ice dams from forming can save you a lot of heartache and expense in the long run.