FEMA Roof Snowdrift Design Guide

This FEMA design guide provides detailed procedures and worked examples for calculating three-dimensional roof snowdrift loads on buildings, consistent with the intersecting drift provisions expected in ASCE 7-22. It explains the evolution of snowdrift design in ASCE 7, highlights changes introduced in ASCE 7-16, and proposes criteria for intersecting drifts at complex roof geometries. The guide includes step-by-step calculations for drift loads, snow densities, drift heights, and drift surcharges, with a focus on real-world building failures and code-compliant design. It is intended for structural engineers and building professionals involved in the design and evaluation of roofs subject to snow loading.