Tech Today

SPRI WD-1


SPRI recently published ANSI/SPRI WD-1, "Wind Design Practice for Roofing Assemblies." This standard provides a recognized consensus-developed methodology for designing wind-uplift resistances for low-slope built-up, polymer-modified bitumen and single-ply membrane roof systems that do not rely on aggregate or paver ballast to provide their wind resistances.

Two-part methodology

ANSI/SPRI WD-1 is divided into two primary parts. The first part addresses how to determine design wind-uplift loads. The second part discusses choosing an appropriate roof system by comparing factored, tested wind-uplift resistance capacities with the design wind-uplift loads determined in the first part.

In ANSI/SPRI WD-1, determining design wind-uplift loads is accomplished using 21 tables based on Building Category II, surface roughness (exposure category), building height (mean roof height) and peak gust wind zone (basic wind speed).