SpecTopics: Fixing the Gutter Gap - Understanding the ANSI/SPRI GT-1 Standard for Gutters
What Is GT-1?
The roof edge is the first line of defense against wind damage in commercial low-slope roofing. Roof edge failures can lead to catastrophic blow-offs, making edge securement a critical design consideration. To address this, the ANSI/SPRI ES-1 standard was introduced in 1998 and established performance requirements for fascia and coping systems. ES-1 provides a uniform test methodology to ensure these components can resist wind loads and maintain membrane securement at the perimeter. Furthermore, ES-1 was adopted into the International Building Code (IBC) in 2003, making compliance mandatory.
However, gutters were specifically excluded from ES-1, leaving a gap in roof edge protection. This gap became evident after RICOWI’s Hurricanes Charley and Ivan Wind Investigation Report, released in March 2006, highlighted gutter failures as a major contributor to roof damage during high-wind events.
To close this gap, the ANSI/SPRI GT-1 Test Standard for External Gutter Systems was introduced in 2016 and adopted into the IBC in 2021. GT-1 ensures gutter systems meet rigorous performance requirements by providing a uniform methodology for testing their wind and environmental load resistance. This advancement helps prevent perimeter failures and improves overall roof system resilience.
How Does GT-1 Work?
GT-1 consists of three primary test methods:
These tests use full-size gutter samples (8 to 12 feet) installed with brackets, straps, and fasteners exactly as they would be in the field, ensuring real-world performance. To complete the testing, loads are applied 12” on center, held for 1 minute, then reduced to zero “until the specimen stabilizes, or for five minutes, whichever happens first”. 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. Failure is defined as the loss of securement of any component (fasteners, bracket, straps, etc.) or permanent deformation of the gutter if it stretches.
Where Does It Appear in the 2021 International Building Code (IBC)?
GT-1 requirements appear in IBC Section 1504.5.1, mandating that gutters securing the roof perimeter on low-slope roofs be tested to resist wind loads per GT-1 methods. While adoption varies by state, more than 20 states have adopted the 2021 IBC and enforce GT-1 compliance, and others are following suit.
What Does Carlisle Provide? Carlisle offers a full line of prefabricated water control products, including gutters, downspouts, scuppers, and collector boxes. They are included in the Edge-to-Edge Total System Warranty alongside the roofing system. Building owners receive single-source coverage for the entire roof system, eliminating gaps in protection and providing peace of mind in the event of a warranty claim.
Final Thoughts
As severe weather events become more frequent, GT-1 compliance isn’t just a code requirement, it’s a best practice for resilience and safety. The roof perimeter is the most vulnerable part of a low-slope roofing system, and history has shown that failures start at the edge.
The ANSI/SPRI ES-1 standard, adopted into the IBC in 2003, was a major milestone in improving roof edge security. By establishing uniform test methods for fascia and coping systems, ES-1 helped ensure these critical components could withstand wind loads and maintain membrane attachment. ES-1 compliance remains essential for protecting the roof edge and preventing catastrophic blow-offs.
However, gutters were excluded from ES-1, leaving a gap in perimeter protection. The industry problem was clear: gutters were a weak link in roof edge security. The introduction of ANSI/SPRI GT-1 in 2016 and its subsequent adoption into the IBC in 2021 closed the gap by providing a standardized method for testing the performance of gutter systems against wind pressures. GT-1 represents a significant step forward in comprehensive roof edge performance.
Carlisle delivers GT-1-compliant products backed by an Edge-to-Edge Total System Warranty, ensuring single-source coverage for the entire roofing system. By specifying ES-1-tested fascia and coping along with GT-1-tested gutter systems, designers can meet modern building code requirements, reduce risk, and deliver long-term performance and peace of mind.
For More Information, Check Out These Resources:
ANSI/SPRI GT-1 Test Standard for External Gutter Systems
Carlisle's Edge Metal and Water Control Products
Contact Amanda Starner with questions.
The roof edge is the first line of defense against wind damage in commercial low-slope roofing. Roof edge failures can lead to catastrophic blow-offs, making edge securement a critical design consideration. To address this, the ANSI/SPRI ES-1 standard was introduced in 1998 and established performance requirements for fascia and coping systems. ES-1 provides a uniform test methodology to ensure these components can resist wind loads and maintain membrane securement at the perimeter. Furthermore, ES-1 was adopted into the International Building Code (IBC) in 2003, making compliance mandatory.
However, gutters were specifically excluded from ES-1, leaving a gap in roof edge protection. This gap became evident after RICOWI’s Hurricanes Charley and Ivan Wind Investigation Report, released in March 2006, highlighted gutter failures as a major contributor to roof damage during high-wind events.
To close this gap, the ANSI/SPRI GT-1 Test Standard for External Gutter Systems was introduced in 2016 and adopted into the IBC in 2021. GT-1 ensures gutter systems meet rigorous performance requirements by providing a uniform methodology for testing their wind and environmental load resistance. This advancement helps prevent perimeter failures and improves overall roof system resilience.
How Does GT-1 Work?
GT-1 consists of three primary test methods:
- G-1: Tests resistance to outward wind loads on the gutter face.
- G-2: Tests resistance to upward wind loads on the gutter bottom.
- G-3: Tests resistance to downward loads from ice and water accumulation on the gutter bottom.
These tests use full-size gutter samples (8 to 12 feet) installed with brackets, straps, and fasteners exactly as they would be in the field, ensuring real-world performance. To complete the testing, loads are applied 12” on center, held for 1 minute, then reduced to zero “until the specimen stabilizes, or for five minutes, whichever happens first”. 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. Failure is defined as the loss of securement of any component (fasteners, bracket, straps, etc.) or permanent deformation of the gutter if it stretches.
Where Does It Appear in the 2021 International Building Code (IBC)?
GT-1 requirements appear in IBC Section 1504.5.1, mandating that gutters securing the roof perimeter on low-slope roofs be tested to resist wind loads per GT-1 methods. While adoption varies by state, more than 20 states have adopted the 2021 IBC and enforce GT-1 compliance, and others are following suit.
What Does Carlisle Provide? Carlisle offers a full line of prefabricated water control products, including gutters, downspouts, scuppers, and collector boxes. They are included in the Edge-to-Edge Total System Warranty alongside the roofing system. Building owners receive single-source coverage for the entire roof system, eliminating gaps in protection and providing peace of mind in the event of a warranty claim.
Final Thoughts
As severe weather events become more frequent, GT-1 compliance isn’t just a code requirement, it’s a best practice for resilience and safety. The roof perimeter is the most vulnerable part of a low-slope roofing system, and history has shown that failures start at the edge.
The ANSI/SPRI ES-1 standard, adopted into the IBC in 2003, was a major milestone in improving roof edge security. By establishing uniform test methods for fascia and coping systems, ES-1 helped ensure these critical components could withstand wind loads and maintain membrane attachment. ES-1 compliance remains essential for protecting the roof edge and preventing catastrophic blow-offs.
However, gutters were excluded from ES-1, leaving a gap in perimeter protection. The industry problem was clear: gutters were a weak link in roof edge security. The introduction of ANSI/SPRI GT-1 in 2016 and its subsequent adoption into the IBC in 2021 closed the gap by providing a standardized method for testing the performance of gutter systems against wind pressures. GT-1 represents a significant step forward in comprehensive roof edge performance.
Carlisle delivers GT-1-compliant products backed by an Edge-to-Edge Total System Warranty, ensuring single-source coverage for the entire roofing system. By specifying ES-1-tested fascia and coping along with GT-1-tested gutter systems, designers can meet modern building code requirements, reduce risk, and deliver long-term performance and peace of mind.
For More Information, Check Out These Resources:
ANSI/SPRI GT-1 Test Standard for External Gutter Systems
Carlisle's Edge Metal and Water Control Products
Contact Amanda Starner with questions.
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