Roof Assemblies
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
section refutes 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 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, 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.
RoofingCode: Section 1505