Will Predicted Heavy Snow Bring a Repeat in Roof Collpases in Winter 2011-2012?

At least three major weather forecasting services are calling for severe snowfall in many areas of the US for winter 2011-2012.  ExactaWeather.com is predicting extremely cold temperatures and exceptional levels of snow for many parts of the US.   AccuWeather thinks storms will develop along  the east coast and quickly move northeast.  Overall AccuWeather projects heavy snow in the Front Range of the Rockies, the Appalachians, along the I-95 corridor, across the Midwest and throughout the western Great Lakes.  NOAA thinks it is a little too early for solid predictions but noted that if enough cold air and moisture are in place, areas north of the Ohio Valley and into the Northeast could see above-average snow. The accompanying map provides a predicted snapshot view of precipitation this winter as generated by NOAA.

 Roof Failures and Collapses in 2010-2011 

Storm patterns from last year brought many areas, particularly in the Northeast, enough accumulated snow to cause large numbers of roof collapses and building failures.   Normally winter storms target the usual category of  “at risk” structures including those that are older and suffer from deterioration or other defects in addition to being designed based on older codes with lower roof snow load criteria.  In general, buildings with  flat and low slope roofs, particularly longer spans, as well as those susceptable to severe drift conditions are often of concern in storms with considerable snowfall or as snow accumulates over time. 

The winter of 2010-11 went beyond the usual and collapsed more than old barns and lightweight cantilevered awnings.  Massachusetts for example, experienced a record of over 100 of roof collapses with snow targeting engineered metal buildings, various commercial structures, industrial garages, schools and even a historic wood lamella riding arena in Ashland.  Residential structures were not particularly impacted although many homeowners took to cleaning off their roofs and many others wondered when they should follow the example of their neighbors. 

Are Roof Strucures in Danger of Collapse Again This Year?

Many studies and reviews of the magnitude of the snow from this past winter are still in progress.  The question remains as to if the ASCE 7 ground snow loads and roof snow load requirements were exceed this past winter and what the impact on code snow maps will be in the future.  While larger than normal snow falls are being predicted for a number of areas this winter, no one can confirm for sure if extreme weather conditions will come together in winter 2011-12 to produce snow overloads and roof collapses.  All  we can say at this point is that early indications are present that should lead all building owners to be cautious, taking steps to be prepared and have a disaster response plan updated and  ready to put in place.

Check back soon for warning signs of a roof snow failure and criteria to watch for roof snow loadings



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