Section 1505.2, Wind resistance of low-slope roof systems

The low-slope roof systems described in Section 1507.5 which are mechanically attached, adhered to the roof deck or ballasted shall be designed to resist the design wind load pressures of Section 1609.0. Roof systems with built-up, modified bitumen, fully adhered or mechanically attached single-ply, metal panels, and other types of membrane roof coverings shall also be tested in accordance with FM 4450, FM 4470, UL 580, or UL 1897 listed in Chapter 35.

Interpretation of the Code:

The code implies that roof systems shall be designed and applied in accordance with the wind attachment requirements of Factory Mutual,ASCE and/or UL.This code disputes the common misconception that only Factory Mutual insured buildings require FM wind attachment standards.Wind uplift calculations should be completed for every project.

Proper roof attachment can be determined in accordance with FM requirements or ASCE standard wind-uplift calculations. The procedure to determine the wind uplift pressure rating on specific buildings during the design phase is based a calculation that takes into account the basic wind speed in the geographical area, the ground surrounding the building and the roof uplift pressure at the field of the roof. The building’s height and perimeter construction are also considered. It is the responsibility of the specifier to complete these calculations and to determine the proper wind uplift rating for the building. Only materials and systems that meet the calculated uplift pressures should be applied.