Which zone of a roof is defined as having the lowest uplift pressures?

• A. Field Zone
• B. Perimeter Zone
• C. Corner Zone
• D. Center Zone

Answer: (A)

The effect being tested is how wind-induced uplift varies across a roof surface. Wind flow around a building tends to cause the strongest suction near edges and especially at corners, where flow separation and vortices amplify uplift. The field (central) zone sits away from those edge effects and is relatively sheltered by the surrounding roof planes, so the pressure variations are milder and the uplift is lowest there. Perimeter and corner zones are more exposed to direct wind impact and the complex flow around edges and corners, producing higher uplift pressures. Therefore, the field zone has the lowest uplift pressures, making it the best choice.