Given the serious ice conditions hitting the Houston area and the frozen Northeast, we want to thank roofing expert Mr. Andrew Smith, Director of Field Operations at Roof Leak Detection Co. for contributing this very good explanation of ice dams and the resulting roof leaks and water damage it can cause. The damage this causes is a long-term issue for policyholders as the damage you incur this winter can show up during summer windstorms. These losses can become complicated insurance claims that require the policyholder to prove the cause of loss when water infiltrates the interior of the home.

Ice dams form when roof areas become warm enough to melt snow, typically because of the combination of the insulating effect of snow accumulation and heat loss from conditioned and/or attic spaces. Ice has the unique characteristic of expanding more and more as it becomes colder, while virtually all other solids contract upon falling temperatures. Water is most dense at 4C (39F) and expands both below and above that temperature. Ice has a linear expansion coefficient more than double that of aluminum, one of the most active solids encountered in roof construction.

Water from melted snow can run into ruptures or a breach in the membrane of the roof and will subsequently refreeze. When ice forms within the rupture it will work its way in and under the various plies and will deteriorate a roofing system, whether steep or low sloped. Consequently, the ice can act as a wedge or a ply-bar which can further force the rupture to expand. Similarly, the extreme cold can make the damaged roofing materials brittle thus decreasing the tensile strength of these materials and further the rapid deterioration of the roofing system. During eventual thawing cycle, both the pocketed/blistered water and residual standing water on the roof surface will be drawn through the rupture by “capillary draw” and drive the moisture deeper into the roofing system. Ice-dam related ruptures to roof membrane/underlayment can be exacerbated by the seasonal freeze and thaw cycle that is inherent to northern climates. Damage caused by ice daming to a roofing system can be extremely problematic after a windstorm, as wind pressures are higher on the perimeter and corner areas, and can cause a breach in the fascia, perimeter flashing, underlayment, and the roof surface (steep and low sloped). As ice-daming typically begins at the gutter and eave areas, the process will rapidly migrate upwards and eventually into the building envelope, as seen below. 

Hopefully a better understanding of ice dam water damage will give you information to bring in the proper experts to help with your property insurance claim. If you’re experiencing water damage from frozen pipes, frozen gutters or other winter storm damage or have questions regarding any property insurance related issues, please call 800.321.4488 or contact us to submit a question to one of our public adjuster or insurance claim experts.