© 2005 Door & Access Systems
Publish Date: Spring 2005
Author: Joe Hetzel
Page 70

ASK JOE HETZEL

Wind Load Exposure Conditions

Q: “I’m installing a garage door in an area where I need to know the wind load requirement, but I have found out that the site conditions affect the wind load. How can I determine what site condition to use?”

A: Three basic site conditions affect the wind load on a garage door:
Exposure B is a typical suburban area, surrounded by trees and other structures that provide some shielding from the wind.
Exposure C is either (1) an open area, extending about 1/4-mile or more in any direction, or (2) a site within one mile of the shoreline (ocean/gulf) in a hurricane-prone area.
Exposure D is within 1/4-mile of an inland body of water that is a mile or more across.

Know whether the local code requires a specific exposure for a specific installation. In the absence of a code-mandated exposure, a local professional engineer – or a door manufacturer’s technical staff member – who understands wind provisions may help.

If you can’t cite a local code or find qualified help, DASMA recommends that you assume the site is Exposure B, unless Exposure C or Exposure D can be proven. But note that hills and valleys next to a garage door may affect wind load, and you may need to consult a professional engineer.