The Russo Report: The ‘Achilles heel' of Low-Slope Roofs
While sustainability and “cool” roofing remain hot topics, the traditional role of roofs as one of the primary waterproofing systems for buildings remains the key focus for roofing contractors.
While sustainability and “cool” roofing remain hot topics, the traditional role of roofs as one of the primary waterproofing systems for buildings remains the key focus for roofing contractors.
The ANSI/SPRI ES-1 standard addresses roof edge securement to help prevent it from becoming a potential “Achilles heel” in low-slope roofing performance. FM Global’s Phil Smith has often been quoted as saying that “the integrity of the perimeter flashing is a critical first line of defense against roof failure.”
In 1992, Hurricane Andrew became the third Category 5 hurricane to make landfall in U.S. history, and it caused $26.5 billion in damage - mostly in South Florida. It was also estimated that 75 percent of all building losses were due to roof failure. A study of 145 FM Global built-up roofs showed that 85 failed due to system failure at the roof perimeter. Simply put, the membrane attachment to the deck could not withstand the loads created when these perimeter systems failed during the hurricane.
SPRI knew that more recent post-hurricane investigations by RICOWI consistently showed that, in many cases, damage to a low-slope roof system during high wind events begins when the edge of the assembly becomes disengaged from the building. Once this occurs, the components of the roof system (membrane, insulation, etc.) are exposed. Damage then propagates across the entire roof system by peeling of the roof membrane, insulation, or a combination of the two.
For this reason, SPRI’s landmark ES-1 standard (“Wind Design Standard for Edge Systems Used with Low Slope Roofing Systems”) was developed in 1998. It is currently referenced in Section 1504.5 of the 2003, 2006 and 2009 IBC. The standard provides roof contractors, consultants and others with information for calculating wind load on metal roof edge systems and prescribes the test methods to be used to ensure that the supplied edge system is capable of resisting that load.
A revised version of this key standard-SPRI/FM 4435/ES-1-is being submitted to ANSI and should be approved in October 2011. It combines SPRI and FM Global requirements and provides basic requirements for wind-load resistance testing and design for roof-edge securement, flashing systems and nailers.
The document also provides minimum fascia thicknesses for satisfactory “flatness” and designs to minimize corrosion. It is intended to be used with manufacturers’ specifications and requirements of specific roofing materials and edge systems used in roof assemblies, excluding gutters.
Basically, the latest draft to ES-1 combines the performance requirements included in the current version of ES-1 and has been expanded to include requirements addressed in FM 4435, “Approval Standard for Roof Perimeter Flashing.”
For state-by-state adoption of ES-1 in the IBC, roof contractors can visit www.iccsafe.org/gr/Pages/adoptions.aspx.
Doing a great job on the field of the roof and all the HVAC details doesn’t mean much if your perimeter edge securement fails. Keeping a close eye on this potential weak spot in the roof system can help keep the roof on the building during high wind events.
While sustainability and “cool” roofing remain hot topics, the traditional role of roofs as one of the primary waterproofing systems for buildings remains the key focus for roofing contractors.
The ANSI/SPRI ES-1 standard addresses roof edge securement to help prevent it from becoming a potential “Achilles heel” in low-slope roofing performance. FM Global’s Phil Smith has often been quoted as saying that “the integrity of the perimeter flashing is a critical first line of defense against roof failure.”
In 1992, Hurricane Andrew became the third Category 5 hurricane to make landfall in U.S. history, and it caused $26.5 billion in damage - mostly in South Florida. It was also estimated that 75 percent of all building losses were due to roof failure. A study of 145 FM Global built-up roofs showed that 85 failed due to system failure at the roof perimeter. Simply put, the membrane attachment to the deck could not withstand the loads created when these perimeter systems failed during the hurricane.
SPRI knew that more recent post-hurricane investigations by RICOWI consistently showed that, in many cases, damage to a low-slope roof system during high wind events begins when the edge of the assembly becomes disengaged from the building. Once this occurs, the components of the roof system (membrane, insulation, etc.) are exposed. Damage then propagates across the entire roof system by peeling of the roof membrane, insulation, or a combination of the two.
For this reason, SPRI’s landmark ES-1 standard (“Wind Design Standard for Edge Systems Used with Low Slope Roofing Systems”) was developed in 1998. It is currently referenced in Section 1504.5 of the 2003, 2006 and 2009 IBC. The standard provides roof contractors, consultants and others with information for calculating wind load on metal roof edge systems and prescribes the test methods to be used to ensure that the supplied edge system is capable of resisting that load.
A revised version of this key standard-SPRI/FM 4435/ES-1-is being submitted to ANSI and should be approved in October 2011. It combines SPRI and FM Global requirements and provides basic requirements for wind-load resistance testing and design for roof-edge securement, flashing systems and nailers.
The document also provides minimum fascia thicknesses for satisfactory “flatness” and designs to minimize corrosion. It is intended to be used with manufacturers’ specifications and requirements of specific roofing materials and edge systems used in roof assemblies, excluding gutters.
Basically, the latest draft to ES-1 combines the performance requirements included in the current version of ES-1 and has been expanded to include requirements addressed in FM 4435, “Approval Standard for Roof Perimeter Flashing.”
For state-by-state adoption of ES-1 in the IBC, roof contractors can visit www.iccsafe.org/gr/Pages/adoptions.aspx.
Doing a great job on the field of the roof and all the HVAC details doesn’t mean much if your perimeter edge securement fails. Keeping a close eye on this potential weak spot in the roof system can help keep the roof on the building during high wind events.
