scope:

Introduction

Roof snow loading must be considered for all states in the United States, with the exception of Florida, which has a mapped ground snow load of zero. Snow is the controlling roof load, over wind or roof live load, in roughly half of the states. Specifically, when the ground snow load is 20 lb/ft² or greater, snow loading typically controls for at least some roof structural components.

Snow loading is a frequent and costly cause of structural-performance problems, including collapse. For example, the March 1993 East Coast storm, which cost an estimated $1.75 billion, is one of the fifteen worst natural catastrophes in the United States in terms of insurance claims paid. As shown in Table I-1, this 20-state storm, also called the "Blizzard of the Century," was more costly than the Oakland Hills fire and Hurricanes Fran and Iniki, as well as the Loma Prieta earthquake, with $960 million in estimated insured losses. Although the winter of 1992-1993 was a record-setting season in terms of losses due to snow, a large insurer reports that the following winter (1993-1994) also resulted in substantial losses at a total cost of about $100 million. Hence, snow loading and snow load provisions are something with which structural engineers involved in building design need to be familiar.