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How Low Slope Roof Edge Systems Protect Your Roof

It’s not uncommon for a new commercial roof to cost $250,000 or more. Typically, the roofing system includes insulation, a cover board, the roofing membrane or waterproofing material and all of the fasteners, adhesives and other accessories such as drains, pipe supports, and the roof’s edge system  needed to install the roof, including the roofing contractor’s labor.  

The roof edge system is the visible metal trim at the roofline of most commercial, industrial and institutional facilities that outlines the building’s perimeter. While it may not be given much forethought, the roof’s edge system is a critical component of a commercial roofing system. The edge metal serves several purposes including acting as an effective termination and transition between the roofing system and the other building components. More important, it serves as the roof’s first line of defense against wind and water infiltration.

After several major hurricanes in the early 2000s, studies and analysis of roofing damage conducted by the Roofing Industry Committee on Weather Issues (RICOWI) in conjunction with Factory Mutual (FM) and SPRI reported that nearly 60% of damage to roofs was caused by failure at the perimeter. In fact, they reported that of the analyzed roof failures, the vast majority of those were caused by poor workmanship and/or substituted materials. The findings are clear: when the perimeter edge metal fails, the roofing system cannot withstand the associated wind loads and progressively fails as well.

What Does This Mean for FMs?

Facility managers and commercial roofing specifiers need to be adamant about maintaining the edge metal specification when value engineering questions arise.  All too often, an engineered edge metal system which has been designed and tested to meet the building code standard, is “substituted” for a product which has not been tested and which may not meet local building code requirements. Such materials are often supplied by the roofing contractor who either bent the metal in their own shop or had it supplied from a local sheet metal supplier.

The International Building Code requires commercial roofs to have an edge system that meets the ANSI/SPRI/FM 4435 ES-1 standard. This standard evaluates edge metal systems based on a variety of factors such as cleat or rail designs, gauge of the metal used, number and placement of fasteners, and profile design, among others. Each design is assigned a performance rating based on the results of the ES-1 testing.  The assigned performance ratings are necessary since there are a variety of important factors for a properly designed roof including wind speed, building height, building exposure, and building use. 

While locally supplied edge metal may look similar to pre-engineered edge systems, the differences can be staggering.  There are relatively few contractors who have been approved for supplying edge metal that meets ANSI/SPRI/FM 4435 ES-1.  For those who have been “approved” through the National Roofing Contractors Association programs, it is important to understand that just because a contractor’s edge metal meets certain aspects of the standard does not mean that it meets the minimum performance requirements for your specific building. For example, your building may require an edge metal system that has passed 150PSF through ES-1.  It is possible to have a particular edge metal assembly that “meets ES-1” but has only passed 90PSF, which would be inadequate if 150PSF is required for the pressures on your particular roof.  It’s important to recognize that “meeting ES-1” isn’t the only piece of the puzzle – it’s not a simple matter of “pass/fail” as the statement “meets ES-1” seems to imply.   Furthermore, it is important to understand that just because a contractor or local metal shop has a limited number of profiles that have been tested to ES-1, does not mean that every edge product they make carries the same rating.  All products must be tested individually, not just the fabrication facility.

The bottom line is that roof edge systems in the specification are designed to meet the specific load requirements of a particular building and abide by the ANSI/SPRI/FM 4435 ES-1 standard. Facility managers should be very wary of “value engineering” this component of the roof, as it is the roof’s first line of defense.

Jason Hildenbrand is the director of sales for OMG EdgeSystems in Asheville, NC. For more information, please visit 

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