Facing the wind

Nailer attachment is one key to achieving good wind-uplift performance

It has long been widely recognized roof membrane blow-off often is caused by inadequate attachment of edge flashings and copings (see Photo 1). A few decades ago, it was common for edge flashings to be attached with cleat clips or to be uncleated. The NRCA Roofing and Waterproofing Manual's 1989 edition and the Sheet Metal & Air Conditioning Contractors' National Association's Architectural Sheet Metal Manual's 1987 edition permitted 4- and 5-inch uncleated vertical faces of edge flashings.

Eventually, it was recognized edge flashings are susceptible to blow-off when they are attached with cleat clips or are uncleated. However, Hurricane Hugo investigations of which I was a part revealed many failures of edge flashings and copings that had continuous cleats. Several of my Hugo recommendations were incorporated into ANSI/SPRI ES-1, "Wind Design Standard for Edge Systems Used with Low Slope Roofing Systems."

Until about a decade ago, it was common for edge flashings and copings to be weaker than the nailers to which they were attached. But with the incorporation of ANSI/SPRI ES-1 into the 2003 edition of the International Building Code (IBC), this has changed. Since the publication of ANSI/SPRI ES-1 in 2003, wind damage investigations have revealed instances where nailers were the weak link in the uplift load path. This is not a new finding (see Photo 2). However, because ANSI/SPRI ES-1 increased attention to edge flashing and coping attachment, nailer failure will become the predominate edge failure mode unless attention also is given to nailer attachment.

ANSI/SPRI ES-1 changes