Snow-Related Roof Collapses—Several Case Studies

Heavy snowfall in the winters of 1993–94 and 1995–96 triggered numerous collapses in the northeastern part of the United States. This paper presents three case studies that were investigated by the writer's firm. Topics covered for each case study include specific climatological. circumstances, comparison to code provisions, results of structural analyses, and lessons learned. In each case, it appears that the snow load on the roof exceeded the design value given in the governing building code, by a greater margin than might be expected from the amount of precipitation alone. Issues needing additional research are also identified, such as accumulation on cold roofs, effects of freezing and thawing cycles, snow drifting on large roofs, and the effectiveness of bracing provided by standing seam roofs.