As most seasoned CAT adjusters are migrating to the Boston area to address the first significant activity of the 2015 storm season, many new guys from the south may be scratching their head and wondering what an Ice Dam is and why adjusters are talking about them lately.
First I want to describe what is occurring and how damage is incurred from them.
It all starts with heavy snow fall. When a foot of snow or more begins to accumulate on a roof, conditions begin to develop to form an "ice dam". As you continue to heat your home, the roof will have some amount of heat that is dissipated up into the layer of snow above. This will melt the snow and create water on the roof surface under the snow.
This water will travel the slope of the roof where the heat is somewhat consistent. Here is the important part though. When the water hits the area of the eves, that underlying heat is no longer present. The water can then turn into ice when it is just above the eve on the home. As this process continues to occur, you begin to build layer upon layer of ice above the eve. This can continue to fill to the point where there is no slope present above the eve. We have now created what is referred to as an "ice dam". Now when water travels under the snow and hits the "ice dam" it will back up onto the roof. We now have an unnatural flow of water that your shingles were not designed to prevent. Water can then back up and penetrate the roof surface in some instances bringing water into the attic. This water will follow a natural flow and show evident in ceilings and walls underneath.
Building code now dictates in areas of cold weather that you install an "Ice shield" on your roof. Basically this is a layer of plastic or rubber that is replacing the bottom row of felt paper on the roof. It is normally sold in a 36 inch roll that you place directly onto the decking around the eves of the roof.
The primary defense of "ice dams" forming on a roof is a well insulated and ventilated attic. By minimizing the heat that is escaping into the attic space and allowing proper ventilation of the entire attic space, you can minimize the ability of an "ice dam" to form. A properly vented attic will have venting at both the high and low points of the attic allowing heat to rise and escape without allowing much of a heat variance in the attic from the outside temperatures.
As an insurance adjuster, it is important to understand how damage occurs so you can articulate to all parties involved what happened on a claim. It is important that the homeowner understands the issue so that it may be prevented in the future.
Until your next storm….continue to learn.