Flat Roof Snow Loads are Primary Concern in East Coast Storm: AIR

Chris Westfall
Chris Westfall

Boston-based modeling firm AIR Worldwide said beyond expected business interruption, roof collapse may be the most likely cause of insured losses from a major snow storm currently battering the U.S. East Coast.

Forecasters are predicting up to 20 inches of snow around the major metropolitan areas of Washington D.C., Philadelphia and New York by time the storm dissipates sometime during the evening of February 10.

This follows a large storm that dumped similar amounts of snow on the U.S. Mid-Atlantic states earlier in the week.

“Ten to 20 inches of snow can lead to loads of roughly 15 to 30 pounds per square foot on flat roofs, but that calculation does not account for snow drift, which can significantly increase loads,” said Tim Doggett, Ph.D, principal scientist for AIR in a statement.

According to an AIR statement, flat roof buildings in the United States are designed to withstand snow load minimums established by the American Society of Civil Engineers depending on their geographic location. The load minimums range between 0 pound per square inch (Florida) to 100 pounds per square inch (Maine.)

However, AIR said that since multiple storms have come in quick succession there little time for the accumulated snow pack to melt. For cities like Washington D.C where the minimum load is about 30 pounds per square foot the accumulation could lead to roof failure.

“With the drifting that accompanies high winds, many roofs will be at risk of collapse,” Doggett said.