Roofing professionals have long recognized the importance of proper low-slope roof edge and gutter designs, particularly in high-wind conditions. For this reason, SPRI has spent more than a decade enhancing test and design standards for these roofing details. SPRI introduced the first version of its landmark standard, ANSI/SPRI/ES-1 “Wind Design Standard for Edge Systems Used with Low Slope Roofing Systems,” in 1998. ANSI/SPRI ES-1 prescribes methodology for testing roof edge assemblies, excluding gutters, to evaluate their resistance to wind loads.
SPRI addressed roof gutters used as edge securement in 2010 with the development of ANSI/SPRI GD-1. This document was separated into two different standards, : a test standard and a design standard. After two years of initial development, the test standard ANSI/SPRI GT-1, “Test Standard for External Gutter Systems,” was approved as an American National Standard on May 25, 2016. ANSI/SPRI GT-1 was reviewed and reaffirmed in July 2022.
ANSI/SPRI GT-1 is a standard load resistance test method for external gutter systems that secures a membrane on commercial low-slope roof systems. ANSI/SPRI GT-1 was added to the International Building Code in 2021, offering a holistic approach to design and testing standards for gutter systems, as gutters are an integral part of the roof edge system.
ANSI/SPRI GT-1 provides a consensus for an acceptable level of performance with real-world practicality. Design professionals, fabricators, and installers must understand the ANSI/SPRI GT-1 for testing information on wind load resistance and roof edge securement. Overall, the main goal of having ANSI/SPRI GT-1 is to protect owners, occupants, architects, and installers by providing a universal guide for consistent performance.
ANSI/SPRI GT-1 provides a test method that can be used by manufacturers of gutters, including contractors that brake or roll form gutters, to determine if the gutter will resist wind loads. Installing gutters tested to resist anticipated wind forces can give contractors peace of mind and may provide a competitive advantage when presented to the building owner.
The tests include full-size and length samples (minimum 8 ft. and maximum 12 ft.) of gutter with brackets, straps, and fasteners installed per the gutter design. It is critical that the gutter be installed with the same brackets, straps, and fastenersat the same spacing and locations as per the tested design to ensure the gutter will perform in the field as tested.
ANSI/SPRI GT-1 consists of three test methods, G-1, G-2, and G-3. Test method G-1 tests the resistance to wind loads acting outwardly on the face of the gutter, and G-2 tests the resistance to wind loads acting upwardly on the bottom of the gutter. G-3 tests resistance to the loads of ice and water acting downwardly on the bottom of the gutter. Even though G-3 is part of ANSI/SPRI GT-1 testing, only G-1 and G-2 are directly cited in the 2021 IBC. Tests G-1 and G-2 are cycled (load, relax, increase load) tests to failure. In ANSI/SPRI GT-1, the loads are increased in 15 lbs/lf increments from 0 to 60 lbs/lf, then in 5 lbs/lf increments from above 60 lbs/lf to failure.