The winter months bring us a more heightened awareness of what a major snowstorm can do to our commute to school or work and, our voicemails if we are a property manager. However, with the heavy snow comes a very real potential for structural failure of a condo association’s roof system that may have tragic results.
We have all seen on the news where a roof has experienced a complete or partial collapse after a heavy snowstorm. The cause, referred to as, “excessive snow load” can result in significant structural and property damage and may result in injury.
Typically, it is only a report of a water leak that brings attention to our roofs in the winter months. Many times the leak is the result of ice damming in the gutter or melting snow entering into a vent. However, sometimes the leaks may be from movement of the structure due to the weight of the snow and ice.
On steep sloped roof systems, excessive snow loads are usually the result of wind creating large snow drifts but they also may be from large accumulations of wet snow from one or several storms. Excessive snow loads most often occur in valleys or at a stepped location against a wall. Additional snow load as well as an impact load with force can also occur when snow or ice slides off a sloped roof onto a lower roof.
These scenarios can create concentrated loads on roofs that are well in excess of the loads imposed by uniformly distributed snow and that may exceed the design loads. Winter rain storms after a snow event and resulting ice accumulation can further increase roof loads and the associated risks. It is important to realize that that each roof has its own unique characteristics and design standards for snow loads. Remember, only an expert with experience calculating snow loads and design of roof structures should design a roof system or assist with a particular repair.