Responsibility Of Snow Drift Load Calculations
Question:
Is the truss designer or the building designer responsible for calculating snow drift loads on a roof system?
Answer:
It is the building designer's responsibility to supply snow drift loading information. Section 3.0 of SBCA’s TTB – Standard Responsibilities in the Design and Application of Metal Plate Connected Wood Trusses outlines what is expected from the five parties involved in the design process: the building owner, the building designer, the contractor, the truss manufacturer and the truss designer. Use of this document is completely voluntary and is not enforced by any agency or building code. The document is, however, in conformity with section 2 of the Truss Plate Institute's ANSI/TPI 1, which is a code-referenced standard.
It might be a good idea for the truss manufacturer to point out to the building designer the missing snow drift loading information before the trusses are designed and manufactured. This will avoid the loading from being overlooked entirely.