By Joel W. Schachter
Professional Engineer,
Precise Home Inspections, L.L.C
www.precisehomeinspections.net

Next time you go outside to admire those big icicles dangling from your gutters this winter, don't think of them as one of nature's wonders or a wintertime delight. Houston, you have a problem! That iciclle may be the product of an ice dam that can significantly damage your house. 

What causes an ice dam? 

An ice dam occurs when the melting snow begins to flow over the edge of a roof. As it travels over the warmer part of the roof, it stays melted. But when it hits the overhanging gutter which is colder, it freezes, either in the gutter or along the roof’s overhanging edge. When the home's heat melts more snow on the roof,  the water has no place to go since the ice dam literally blocks the water from running over the edge of the roof. The water, still liquid and with no place to go, begins to back up under the roofing shingles. Any leak path will allow this water to penetrate the house structure and usually enter the hollow wall under the dam. A sure sign that a problem can exist are the tell-tail icicles that are beautiful to look at but indicate a potential problem. 

What are the ramifications of an ice dam?
As a house inspector I look for telltale signs around the walls and ceiling corners. If they're stained with water, I can usually attribute this to a former ice dam. It is important to note that this type of problem is not an indication of a faulty roof and should not be interpreted that the roof needs repairing.

How to prevent ice dams?
One way is to turn the heat way down in your house and move to Florida for the winter. But the best way to guarantee no ice "dam-age" is to install heating (de-icing) cables along the edge of the roof, in the gutters and down through the downspouts. These de-icing cables reduce the ice dam buildup by creating channels that allow the water to drain into gutters and down the downspouts. You probably have seen them from those zigzag patterns on your neighbor’s roof. This time of the year, you can purchase de-icing cables at any hardware store, however, the installation should be left up to a professional roofer.

Another way to minimize the chance of ice dam damage is to keep the attic as cold as possible to reduce the chance of melting the snow. This can be done by over-insulating the attic and providing for increased ventilation. The resulting temperature on the roof deck will be so low that the snow on the roof will not melt. 

For more information on preventing or mitigating ice dams, Contact Joel Schachter at joelschachter1@aol.com, or call Joel at 917-279-6725.