Originally Published: May 2024 | Updated: October 2025 

Factory Mutual (FM) (FM)has modernized its RoofNAV system by replacing legacy wind uplift ratings (Class 60, 90, 120, etc.) with measured test pressure values as the new industry standard for roof system performance. FM began converting listings in 2024, and by mid-2025 the transition is in progress. 

This change gives specifiers, architects, engineers, consultants, and contractors a more precise, transparent, and code-consistent basis for the design, evaluation, and selection of compliant roof systems. 

Instead of relying on broad classification labels, professionals can now access exact uplift and outward pressure values (psf) — values that can be directly compared to calculated design wind loads using American Society of Civil Engineers’ ASCE 7 and the International Building Code (IBC). 

Why Test Pressures Instead of Ratings?

Traditional FM wind uplift ratings (Class 60, 90, 120) were broad categories that could create ambiguity or overgeneralization. 

By contrast, test pressures measure the actual forces a roof assembly must resist (in pounds per square foot, psf). This enables: 

• Direct comparisons between calculated building design pressures and tested assembly capacities. 

• Alignment with ASCE 7 and the IBC, which define wind loads exclusively in psf values. 

• Improved clarity in specifications, ensuring that the specified system meets or exceeds design loads.  

For professionals responsible for roof design, this update simplifies evaluation, reduces uncertainty, and supports high-performance, code-compliant, and long-lasting systems.  

What Are the New FM Requirements for Gutters?  

FM has also advanced requirements for gutter system testing, aligning them with the ANSI/SPRI GT-1 Test Standard for External Gutter Systems.  

To achieve FM Approval, gutters must now meet these minimum test pressures: 

• G-1 (horizontal load): 58 psf 

• G-2 (vertical load): 101 psf 

• G-3 (downward load): 62.4 psf 

All gutters listed in RoofNAV were required to be retested and relisted by July 2024. As of 2025, FM has removed non-compliant listings and only recognizes gutters that have been tested using the updated test methods and meet these thresholds. 

FM also revised DS FM 1-49 Perimeter Flashing to reflect the pressure-based approach, ensuring consistency between RoofNAV listings, design standards, and insurance requirements. 

RoofNAV Platform Enhancements 

FM’s updates extend beyond test values. In late 2024, FM introduced a major RoofNAV interface upgrade designed to streamline navigation and improve usability. Enhancements include: 

• Advanced search filters and tools for faster assembly selection. 

• A redesigned Ratings Calculator, now based on pressure values rather than ratings. 

• Expanded assembly pages showing both vertical (uplift) and horizontal (outward) pressure values. 

These upgrades reduce time on the platform and allow roofing professionals to evaluate assemblies in the same terms and units referenced in building codes and engineering standards. 

FM Approval vs. ANSI/SPRI Testing: What’s the Difference? 

A common question in commercial roofing is whether passing ANSI/SPRI/FM 4435/ES-1 (ES-1) or ANSI/SPRI GT-1 (GT-1) testing automatically qualifies a product for FM Approval. 

Does ES-1 or GT-1 Equal FM Approval?

No. While the test methods are similar, passing ES-1 or GT-1 testing for compliance does not equal FM Approval. FM requires its own certification process, including FM laboratory testing, audits, and RoofNAV listing. 

What Is Required for FM Approval? 

FM Approval is a formal certification process that goes beyond ANSI/SPRI testing. It includes: 

• Performance testing in FM laboratories under FM protocols 

• Marking requirements for approved products 

• Examination of manufacturing facilities  

• Audit of quality assurance procedures 

• Surveillance programs with annual inspections 

• Formal listing in the FM RoofNAV database 

What Are ANSI/SPRI Standards? 

ANSI/SPRI testing standards are building code requirements for commercial low-slope roof systems, whether or not the building is FM insured: 

• ES-1 (ANSI/SPRI/FM 4435/ES-1): Required by the IBC since 2003 for fascia and coping systems on commercial low-slope roofs. Adopted nationwide. 

• GT-1 (ANSI/SPRI GT-1): Added to the IBC in 2021 for gutter systems. Adoption continues to expand across states and municipalities.  

Manufacturers can test products to ES-1 or GT-1 at accredited facilities. If the product passes, it is accurate to say that it is ES-1 tested or GT-1 tested. However, this is not equivalent to FM Approval. 

Key Distinction 

• ES-1 and GT-1 = Building Code Compliance (required by IBC) 

• FM Approval = Insurance Certification (required for FM-insured facilities) 

Both are critical, but they serve different purposes in roofing design, construction, and risk management. 

Why This Matters to Roofing Professionals 

FM’s updates provide clearer tools to evaluate and select roofing assemblies and systems with confidence. Professionals can now directly compare:  

• Code-required pressures (ASCE 7 / IBC) 

• ANSI/SPRI test results (ES-1 and GT-1) 

• FM Approval pressures (RoofNAV) 

By aligning test pressures across codes, standards, and insurance requirements, FM has given roofing professionals a more consistent, transparent foundation for designing systems that deliver long-term performance and reduced risk — leading to better outcomes for building owners and occupants. 

Continuing Education Opportunities 

Staying current with industry updates is critical to staying compliant and competitive. 

To learn more about the ES-1 testing standard, visit our dedicated ES-1 Resource Page, and request your Cutting-Edge Code Compliance continuing education seminar, available in-person or virtually.



To learn more about the GT-1 testing standard, visit our dedicated GT-1 Resource Page, and request your Gutters & GT-1 continuing education seminar, available in-person or virtually.