In many parts of the country, the arrival of the new year commonly corresponds with the arrival of concern about the effects of severe winter weather. January through March are often the months during which the most severe snowfall events and ice storms occur. Such events can cause damage to structures, such as damage from the weight of ice/snow or water intrusion damages brought on by the winter weather.
Nelson evaluated multiple structures in the Western United States that experienced historically significant amounts of snowfall during the winter of 2022-23. Snowfall in some areas was on the order of 100″. Such snow accumulation can impart heavy loads on a structure. In some cases, heavy snow loads can lead to collapse (Figure 1). In other cases, the structure is able to support the weight of accumulated ice/snow without collapse, but some interior distress may occur due to the deflection of the roof under load (Figure 2).
Figure 1. Roof collapse due to the weight of snow. This was from a commercial building in Wyoming.
Figure 2. Damage to interior wall finish resulting from weight of snow accumulation at the roof above. Photo from a residence near Lake Tahoe.
Water intrusion from winter weather most commonly occurs as a result of ice damming. Ice damming occurs when accumulated snow on the roof of a building melts due to heat from inside the building and runs down to the roof edge. During periods with freezing temperatures, this meltwater can then refreeze at the roof edge or overhang and begin to accumulate, creating a dam that impedes the drainage of future meltwater. The water that backs up behind an ice dam can leak into the building and cause damage (Figure 3).
Figure 3. Damage from moisture intrusion resulting from ice damming at the roof. This occurred at a residence in Colorado.
In wooded areas, the weight of snow and ice accumulation on trees and tree branches cause additional concern. Figure 4 shows the effects of a tree impact on a residence. The tree fell due to the weight of snow.
Figure 4. Damage related to a fallen tree. The tree fell during a winter storm event.
Nelson’s team of professionals is experienced in assessing structures with damages associated with winter weather events, from the weight of snow to the effects of ice damming.