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The Causes and Cures of Ice Damming

A substantial snowfall is the first element in the building of an Ice Dam. The other factors are many and varied. The interaction of changing outside temperatures, heat lost from the living space to the attic, large overhangs at the eave and even poorly pitched gutters may also contribute to an Ice Dam.
Whenever snow begins to melt, but then re-freezes before it has been channeled off the roof and away from the gutter and drain system, the Ice Dam is born.
The snow in contact with the roof surface melts when the roof surface is warm. The term "warm" is relative. If the roof surface is above 32° F., it is considered warm. A roof surface at 40° F. will cause a bigger ice dam than a roof surface only slightly above 32° F. The source of the heat is the heated home. If the heated home is poorly insulated, heat will escape to the attic area. The attic area, when not well ventilated, will heat the underside of the roof deck causing the temperature of the roof deck to rise.
The solution to the problem in the above scenario is to keep the attic cold. This requires the proper balance of insulation and ventilation. Insulation in new homes should be R-30 in ceilings as per N.Y. State Building Code. Many older homes are poorly insulated or lack a well-ventilated attic, or both. Adding insulation without proper ventilation may not address the problem. The reverse is also true. Ventilation alone may provide no solution. Additional ventilation by itself may worsen the situation by adding a condensation problem. A contractor with expertise is the only true solution.
The re-freezing, which occurs at the roof edges, is also caused by different factors. The absence of a heated roof deck below in the area of the overhang allows the cold water to re-freeze. Since there is no warm attic beneath the overhang, the roof deck is cold. The flowing water freezes as it moves across this surface, the re-freeze may begin right on the roof surface above the shingles, especially on large overhangs. It may start freezing in the gutters, which are clogged, poorly pitched or just laden with snow and cold themselves. The frozen gutter may begin the Ice Dam. Rising temperatures during the day, or warm sunlight often causes Ice Dams if temperatures fall in the evening or periodically during the day.
Removing a large volume of snow from the roof surface, though not always practical or safe for the average homeowner, is one sure way to eliminate the problem. Often the Ice Dam goes unnoticed until it has collected standing water behind it, which backs up under the shingles and flows into the home near the outside walls. If this happens emergency ice removal is needed. This ice chopping to clear a channel through which standing water can escape is only a short-term solution. It often cannot be done without some breakage of the shingles below. Another method of addressing the problem is the installation of Ice and Watershield membrane. Ice and Watershield addresses the symptom of Ice Damming, the application of this rubberized nail hole sealing membrane beneath the shingles should provide a waterproof layer. This material must be installed in the proper manner or it will not work. Proper installation often requires gutter removal and more than one row (36 inches) of Ice and Watershield. Ice and Watershield does not prevent Ice Dams, but it should stop the water behind them from entering the living space.
Contact us at Tucek Roofing if you would like more information, or need an estimate for any roofing related work. (914) 268-5170.

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