Angle of Attack

Roof pitch dramatically affects both the direction and magnitude of wind forces. Low-slope roofs (under 10 degrees) experience mostly uplift suction. As pitch increases, the windward side begins to experience positive pressure while the leeward side still sees suction. Very steep roofs act more like walls, with the windward slope receiving direct pressure pushing down and into the roof structure.

There is no single best pitch, but roofs between 4:12 and 6:12 (18-27 degrees) often balance aerodynamics and water shedding well. Hip roofs generally perform better than gable roofs because they present sloped surfaces to wind from all directions. The key is proper attachment at every connection point, regardless of pitch. Clips, straps, and proper fastening matter more than pitch alone.

Wind flowing over a flat roof creates low pressure above the roof surface, similar to how an airplane wing generates lift. This suction pulls the roof upward. The edges and corners experience even greater suction because wind accelerates as it separates from the building edge. This is why flat roof edges often fail first in high winds.

Steep roofs have different wind loads, not necessarily higher or lower overall. The windward slope of a steep roof receives more direct pressure (pushing down and into the structure), while the leeward slope still experiences uplift. The total force on the structure depends on roof geometry, wind direction, and building shape. Steep roofs often have less edge suction but more direct wind pressure.