Wind Uplift

Certified Commercial Property Inspectors Association.

Definition: Wind uplift refers to the upward pressure or force exerted on a roof by strong winds. When wind blows across the roof, it creates suction that can lift roofing materials away from the roof deck, potentially causing significant damage. Wind uplift is a major concern in areas prone to hurricanes, tornadoes, and other severe wind conditions, and proper design and installation of roofing systems are crucial to mitigate its effects.

How Wind Uplift Occurs:

• Air Pressure Difference: uplift occurs when there is a difference in air pressure between the outside of the building and the inside. As wind moves over the roof’s surface, the pressure above the roof drops, while the pressure inside the building remains higher. This pressure difference creates suction, pulling the roof upward.
• Edge Vulnerability: Roof edges, corners, and eaves are particularly vulnerable to wind uplift because these areas experience higher wind speeds and turbulence. If the roofing materials or fasteners in these areas are not properly secured, wind can get underneath the roofing system, leading to partial or complete roof failure.

Factors Influencing Upliftm Pressure:

• Roof Shape and Slope: Flat or low-slope roofs are more susceptible to uplift because they provide a larger surface area for wind to act on. Steeper roofs may experience less uplift because wind can pass over them more easily.
• Roofing Materials: Different roofing materials have varying levels of resistance to uplift pressure. Lighter materials, like asphalt shingles, are more prone to being lifted by wind than heavier materials, like tile or metal. The way materials are fastened to the roof deck also plays a significant role in their wind resistance.
• Building Location: Buildings in coastal regions or open, flat areas are more exposed to high winds and are therefore more susceptible to wind uplift. Local wind codes often dictate specific construction techniques and materials to account for these conditions.

Wind Uplift Ratings 

• FM Global Wind Uplift Ratings: These ratings are commonly used in commercial roofing to determine a roof’s ability to resist wind uplift. The rating is based on testing that simulates wind forces on the roofing system.
• ASTM Standards: ASTM International provides standards, such as ASTM D3161, which tests the wind resistance of asphalt shingles, giving a rating based on how well the material performs under various wind conditions.