13/01/2023
Ice Dams - Important Information
If you have noticed snow tends to melt on your roof faster than the roofs on your neighbors houses, and that lots of icicles form, it is a good indication that you are at a HIGH risk for ice dams. The more snow, the greater the chance your home will be affected. Minnesota has seen above normal snowfall for the 2022/2023 winter season. In the central Minnesota St Cloud area we have had over 42 inches as of the middle of January, which is almost as much snow as we get in a normal/average winter. The more snow, the more likely an ice dam will form and cause problems in your home.
As a homeowner it is very important to understand what ice dams are, what homes are at risk, how to prevent them from happening, and how to keep your home protected.
Photo from University of Minnesota
When temperatures outside are below freezing, an ice dam will form when warm air in the attic space heats the roof causing snow to melt and water to run down to the eave. When the water reaches the eave and is no longer warmed, it turns to ice. Eventually it backs up forming a pool of water and will flow backwards underneath the shingles finding its way into the attic, insulation, and into your home.
Attics should be sealed to prevent heat loss, have a proper amount of insulation, and good airflow to keep the attic space the same temperature as the outside air. This prevents the snow from melting when temperatures outside are below freezing. Older homes are at a higher risk as they were built before modern building code requirements. Over time airflow can get blocked and insulation can settle.
After a large snowfall, remove snow from the eaves, three to six feet on the roof past the exterior wall, to help prevent the ice dams from forming. Also, make sure that the snow has not covered and blocked the ventilation system along your ridge vent or the box vents. It is better to remove all the snow from the roof if possible. It is important to use the proper tools and take care to prevent gouging or scratching the shingles. Roof rakes and snow removal tools can be purchased at most major stores.
The best long-term prevention is to make sure your home is properly sealed, insulated, and ventilated. Outside air must flow into the attic, usually from the eaves through baffles or chutes into the attic space. Make sure the attic is sealed from the interior of the home and any areas that lots of warm air can escape into the attic are taped or foamed shut. 16 to 20 inches of insulation is recommended. The correct number of box vents or ridge venting should be installed per Minnesota code to allow warmer air to escape through the roof peak.
Common misconceptions about roofs:
When a new roof is installed it will prevent ice dams.
A new roof does not prevent ice dams. Ice dams are formed due to inadequate insulation and ventilation.
Ice and water barrier installed underneath the shingles will prevent ice dams or leaking from ice dams.
A roof is designed to shed water, not hold water. Ice and water barrier installed at the eaves and in the valleys helps protect the roof but will not always prevent water from finding a way through. Ice dams can also damage shingles, lifting them and causing the seals to fail.
For more information see:
Dealing with and preventing ice dams | UMN Extension
https://extension.umn.edu/protecting-home-rain-and-ice/dealing-and-preventing-ice-dams
Ice Dams - Truths and Common Misconceptions - Big League Roofers
https://bigleagueroofers.com/ice-dams-truths-and-common-misconceptions/
