ABSTRACT
Snow is a controlling roof load in about half of all the states in the United States. It is a cause of frequent and costly structural problems. Snow loads are assumed to act on the horizontal projection of the roof surface. Partial loads are different from unbalanced loads. In unbalanced loads, snow is removed from one portion and is deposited in another portion. In the case of partial loading, snow is removed from one portion through scour or melting but is not added to another portion. A sliding snow load from an upper to a lower roof is superimposed on the balanced snow load. It is not used in combination with partial, unbalanced, drift, or rain-on-snow loads. The sliding load (plus the balanced load) and the lower roof drift load (plus the balanced load) are considered as two separate cases, and the higher one is used.
