Winter Ice Dams


This is the time of year in Central Ohio when we get calls about leaks that are occurring because of ice dams. Why do they occur and what can we do to prevent them?

Melting snow from the roof gets trapped at the edge of the roof because of the ice that remains at the edge of the roof. The water collects at this point and is able to enter the house. Your shingled roof depends on shedding water to operate properly; it is not designed to hold water.

The cause can be poor insulation, inadequate ventilation or an improperly functioning gutter. Most of the homes we inspect for ice damming issues have adequate insulation. If the cause of the damming is insulation it is usually because it was installed over the ventilation intake vents or some of the insulation got displaced after the original installation. Most of the time we see ice damming it is because the house is not properly ventilated. The hot attic air gets trapped and heats up the surface of the roof, melting the snow that is resting on it. The water runs down the roof to the eave that is not heated by the attic. There it meets an ice dam and stays there until it melts or is removed.

In most cases the easiest way to prevent them in the future is to properly ventilate the roof. This should be done when the roof is installed, but is often not the case. All that is required is some intake vents at the lowest portion of the roof, which usually means at the soffit (You would see these vents if you were viewing your eaves from the ground). Exhausts vents should be installed at the upper most portion of the roof. These can be ridge vents, shingle vent, hat vents, or possibly a power vent if there is insufficient ridge to install the other vents. Installing proper ventilation allows cooler air to flow through the attic space and out the top. It keeps the surface of the roof closer to the outside air temperature insuring it won't melt before the section of roof at the eave.

There are added benefits to venting the roof as well. By removing the trapped most air from the attic the insulation stays dryer (insulation loses it insulative value when it gets wet) and it also allows the roof to last longer. We can give you expert recommendations based on the specifics of your house and of course this issue is addressed in every roof we install. The other safeguard to ice damming is the installation of ice and water shield. This is a material that will waterproof the section of roof you install it on. The recommendation is that extend at least two feet past the exterior wall at the horizontal plane. Meaning that because of the slope of the roof, more than two feet of material is required. Ice and water shield doesn't prevent ice dams but it will keep water out.

The city of Columbus now requires this for all new roof replacements. What to do if you are experiencing ice dam leakage right now. Some homeowners attempt to alleviate the ice damming as a DIY project. We don't recommend doing that however. Ladders become very slippery when your feet have snow on them. A light colored roof may have an invisible paper thin layer of ice on it that can cause you to slip. The roof is also easily damaged by chopping the ice away. It's better to invest in repairing the source of the problem than its symptoms.




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