ICE RELATED DAMAGE TO BUILDINGS



By
Charles C. Roberts, Jr., Ph. D., P.E.




Figure 1

Figure 1 shows the classic ice dam formation on the eave of a building. The weight of the ice can cause gutter and eave damage. Normal drainage is blocked and can cause water to back up between shingle layers, drain onto ceiling insulation and wallboard as shown in Figure 2.

Figure 2


Figure 3

Figure 3 illustrates the process of ice dam formation. During the day when warmer temperatures are occurring, meltwater drains down the roof toward the gutters. As the evening hours arrive, the eaves, being more exposed, tend to be cooler than the roof area. Meltwater freezes first in area of the eaves. This tends to dam water flow from the roof, resulting in a build-up of ice, hence the ice dam. During the warmer period, liquid water can pond behind the dam and enter the attic space through the seams in shingles. The water then drains onto insulation and eventually causes interior water damage. Buildings with poor ceiling thermal insulation are more vulnerable to this condition since their attics are warmer, which encourages the freeze/thaw cycling, a major ingredient in the development of an ice dam. Some buildings are more vulnerable to ice dam problems by design as shown in Figure 4. The roof on the left in the photo drains toward a valley near a


Figure 4
vertical wall. Water drainage from the large roof on the left is directed against the wall. Any ice dam developing at the discharge end of the valley can cause water to back up and enter the wall structure. Because of the large roof draining into the valley, a large volume of water must be carried by the valley, making the wall vulnerable to water entry. The wire heater helps prevent the ice build up but may not be effective in all conditions. Damage caused by ice dams includes detached gutters, roof structure damage, deterioration, interior water staining, and ice impact damage at lower levels. Personal injury can also occur from impact with falling ice as well as slip and fall accidents relating to ice debris on walkways.


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