This Excel document gives wind load details applicable to Exposure Category B, which reflects urban and suburban regions with high population density. The sheet calculates design wind pressures on structural surfaces based on inputs such as building height, wind speed, and importance factor per standard codes including ASCE 7.

What Is Exposure Category B?

Exposure Category B is defined in ASCE 7 as terrain with surface roughness B prevailing in the upwind direction for a distance of at least 1,500 ft (460 m) or 10 times the height of the building, whichever is greater. This covers urban and suburban areas, wooded terrain, and other areas with closely spaced obstructions having the size of single-family dwellings or larger.

Exposure B represents the most commonly encountered condition for buildings in residential and commercial zones in the United States and is the default assumption in many engineering offices when more detailed terrain assessment is not conducted.

How Exposure Category B Affects Wind Pressures

Buildings in Exposure B experience lower wind pressures at lower heights compared to Exposure C or D because the surrounding obstructions create a thicker atmospheric boundary layer that attenuates wind speeds near ground level. The gradient height for Exposure B is 1,200 ft (366 m) — the elevation above which wind speed is essentially uniform.

Sheet Inputs and Outputs

Inputs:

Outputs:

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Download the Exposure Category B Wind Load Sheet

This sheet is a practical tool for engineers designing structures in suburban and urban environments where Exposure Category B applies. It produces a clean, organised calculation that can be included in a structural design report. Download the free Excel sheet below and complete your wind load calculation efficiently.

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