Building Exposure

Type Exposure Description
B
Exposure B - Urban or Suburban
Area with numerous closely-spaced obstructions having the size of single-family dwellings or larger. For all structions shown, terrain representative or surface roughness Category B extends more than ten times the height of the structure or 800 meters, whichever is greater, in the upwind direction.
C
Exposure C - Scattered Obstructions
Open terrain with scattered obstructions having heights generally less than 30 feet for most wind directions. All one-story structures with a mean roof height less than 30 feet in the photograph are less than 1500 feet or ten times the height of the structure, whichever is greater, from an open field which prevents the use of Exposure B. Also includes shoreline in hurricane-prone regions.
D
Exposure D - Open Water for 1 Mile or More
A building at the shoreline (excluding shorelines in hurricane-prone regions) with wind flowing over open water for a distance of at least one mile. Shorelines in Exposure D include inland waterways, the Great Lakes, and coastal areas of California, Oregon, Washington and Alaska.