Tech Today

A new wind design standard

Late in 2008, SPRI updated ANSI/SPRI RP-4, "Wind Design Standard for Ballasted Single-ply Roofing Systems." The updated edition builds on the standard's 1988 and 2002 editions and includes two significant changes.


The differences between the 2008 edition and the standard's previous editions are the addition of a definition for the term ballast and revision of the description for surface exposure categories that are used with the standard's design tables.

Also, the following statement has been added: "The Design Tables are based on the premise that the ballast will not blow off the roof at the design rooftop wind speeds."