ANSI/FM 4474

ANSI/FM 4474, American National Standard for Evaluating the Simulated Wind Uplift Resistance of Roof Assemblies Using Static Positive and/or Negative Differential Pressures, was developed by FM Approvals (the certification arm of insurer FM, formerly FM Global) and approved as an American National Standard. The 2004 edition was reaffirmed in 2010.

Scope

The standard measures how well a complete roof assembly resists uplift by applying a static pressure difference across it. It applies to:

• standing seam metal roofing
• lap seam (through-fastened) metal roofing
• hot-mopped and built-up roofing
• single-ply membranes

Loose-laid and ballasted systems are outside its scope because they rely on weight rather than attachment.

Test types

ANSI/FM 4474 describes several procedures, including:

• Pull test – a 2 by 2 ft (0.6 by 0.6 m) simulated uplift test, often used for components such as insulation adhesion.
• Pressure uplift tests – on samples of 5 by 9 ft (1.5 by 2.7 m) or 12 by 24 ft (3.7 by 7.3 m), depending on the assembly.

Pressure is increased in 15 psf (0.72 kPa) increments, each held for 60 seconds, until failure.

Relationship to FM Approvals ratings

FM Approvals uses the 12 by 24 ft uplift table in its own approval standards, such as FM 4470 for membrane roofs. Approved assemblies are given ratings such as Class 1-60, Class 1-90 and higher, where the number is the uplift pressure in psf that the assembly withstood (with FM's own safety margin applied in design). These ratings appear in the RoofNav database used by specifiers and insurers.

Code recognition

The International Building Code accepts FM 4474 alongside UL 580 and UL 1897 as a wind uplift test for membrane roof systems. Florida Product Approval and Miami-Dade product control files frequently cite FM 4474 test results.

Practical notes

The test is static, so it does not capture the fluttering and cyclic loading that mechanically attached membranes see in real wind. Designers working in Canada often also look for dynamic test data under CSA A123.21.