It’s good when people can get together and agree on how to solve problems. ANSI (American National Standards Institute – the testing and standards folks), SPRI (Single Ply Roof Industry – the roofing membrane manufacturers and contractors association), and FM Global (the major insurance player in the roofing industry) all got together in recent years to try and solve the biggest source of catastrophic roofing membrane failures – when the terminations at the edge fail and result in subsequent peel back of the system.
The result is the new “Design Standard for Edge Systems Used with Low Slope Roofing Systems” aka ANSI/SPRI ED-1 2019. It was approved on June 3, 2019. This Standard, intended for use by those that design, specify, and manufacturer roofing, provides basic requirements for wind load design for edge securement of roof systems, including gutters and nailers. It provides information on material thicknesses that lead to satisfactory flatness, accommodating thermal movement, how to minimize corrosion, methods for testing, and other factors affecting performance. It applies to low slope membrane roof systems, defined as roofs having a 2:12 slope or less. It addresses design and installation of copings, horizontal roof edges, and gutters as well as the following factors which need to be considered:
- Structural integrity of the substrate that anchors the edge (e.g. nailers)
- Wind resistance of the edge detail
- Material specifications
The Standard provides perimeter edge loads based upon the field of roof pressure for the building under consideration. Pressures should be calculated using ASCE 7 Minimum Design Loads for Buildings and Other Structures or other suitable means of determining the field of roof pressures. You can find the full text here: https://www.spri.org/standards/.