What is an FM Approvals wind test, and what do the various wind uplift ratings mean? This question is frequently asked, but often answered incorrectly. Before we can answer the question, however, we must first define wind uplift.
Roof damage caused by wind occurs when the air pressure below the roofing assembly is greater than the air pressure above the building's roof. As wind flows over the building, the pressure directly above the surface of the roof decreases. At the same time, internal air pressure increases due to air infiltration through openings, cracks, etc. The result is a net upward force on the roofing system. This force is referred to as wind uplift.