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.

ANSI/SPRI RP-4-08

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."

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