Public Release: 

Blizzard Snow Loads And Building Codes

Cornell University

ITHACA, N.Y. -- For building engineers and climatologists, the memory of the Blizzard of '96 refuses to melt away.

Well over a year since the heaviest snow of the century fell over the Northeast, climatological studies now show that had it not been for structures built "better-than-code," more roofs could have collapsed under the weight, researchers say.

"In places where roofs should have collapsed, they didn't collapse," said Arthur T. DeGaetano, a climatologist with the Northeast Regional Climate Center at Cornell University. "It showed that most buildings exceeded the minimum building code requirements."

The Blizzard of '96 (Jan. 8-10, 1996) was a whopper, but with snow resting on rooftops, another smaller storm followed and contributed to even greater snow weight on roofs. "It snowed, stayed cold, and we got more snow," DeGaetano said. "It was the accumulation of snow from the two storms that posed the snow weight problem."

Enough snow fell throughout the 1995-96 season, that Boston, New York City, Philadelphia, Baltimore, and the greater Washington area smashed their snowfall records.

But, during the Blizzard of '96, news reports of roof failures throughout the Northeast corridor -- Boston to Washington -- prompted DeGaetano; Thomas W. Schmidlin, associate professor of geography, Kent State University; and Daniel S. Wilks, Cornell associate professor of meteorology, to author a peer-reviewed paper, "Evaluation of East Coast Snow Loads Following the January 1996 Storms," in the Journal of Performance of Constructed Facilities (May 1997), a publication of the American Society of Civil Engineers, New York City. The study was funded by the National Oceanic and Atmospheric Administration.

DeGaetano and the other scientists examined the weight of snow during the period Jan. 6-15, 1996. Once the snow weights were determined based on water content within the snow, they corroborated the climatological information with minimum building codes for given areas. For example, some of the hardest hit areas were northern and central New Jersey.

For northern New Jersey, building-code minimums generally require roofs to withstand snow weights of 21 pounds per square foot -- the equivalent of a storm that occurs once every 50 years. More infrequent storms bring snow weights of 26 pounds-per-square-foot in 100-year events, and 31 pounds-per-square-foot for 200-year values. The Blizzard of '96 and the subsequent storm amounted to the equivalent snow weight of a 125-year snowstorm.

Coastal Maine has different code requirements, as their 50-year snow weight level is 62 pounds-per-square-foot, their 100-year snow-weight level is 72 pounds-per-square-foot, and their 200-year mark is 83 pounds-per-square-foot. Snow weights here did not exceed the code.

In areas south of Boston, the researchers found that snow weights exceeded the minimum building requirements.

The Philadelphia building inspector's office reported 55 collapses, mainly from porches and rowhouse roofs. In Camden, N.J., there were 16 reported porch and rowhouse roof collapses. These types of structures, however, are often not covered by building code requirements, or pre-date the establishment of these standards.

Staggered news reports during the Blizzard of '96 and the subsequent snow storms provided the scientists with anecdotal information as well, lending insight to the type of structures and geographic locations to pay attention to. For example, a barn collapsed in Woodsboro, Md., killing 150 cows inside; a supermarket roof collapsed in Massapequa, N.Y., injuring 10 people; a 2,500-square-foot section of shopping mall collapsed in Tewksbury, Mass.; a building that housed a printing company in Bethesda, Md., completely collapsed; and a lawn and garden shop in Berks County, Pa., collapsed under the snow weight, killing one person.

"Climatology affects a lot of different fields, someone has to show how much snow can fall and what an engineered-structure can handle," DeGaetano said. "You have to ask what's the maximum snow weight that a roof can hold, what's the frost depth for underground utility lines, what's the max winds in an area so that roofs can withstand the winds, what's the maximum rainfall for an area, so that sewers can handle rainfall. That's what climatology is all about."


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