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How to Calculate Windload on Permeable Fence

Cheryl Ess

When wind hits a solid fence, it is diverted over and around the fence. A concrete block wall is an example of a solid fence. When wind hits a permeable fence, it can go through the fence as well as over and around it. A picket fence is an example of a permeable fence. When wind hits either a solid or permeable fence, it puts a force on the fence known as wind load. Wind load affects the fence design.

Permeable fencing can stop a horse, but not the wind.

Step 1

Determine the maximum wind speed in the area where you want the fence. The "Guide Specifications for Design of Metal Flagpoles" includes a map showing maximum wind speeds in the United States. This guide is issued by the American National Standards Institute and the National Association of Architectural Metal Manufacturers and is available online. Take a fence in a midwestern area as an example. The maximum wind speed there is 90 mph.

Step 2

Decide on the type of permeable fence you want. The example fence is chain link.

Step 3

Find an Internet site for calculating wind load on the type of permeable fence you selected. Many fence manufacturers have such sites. Some sites allow you to enter inputs and then display the output. Others provide documents describing how to do the calculation. Still others provide look-up tables. Use the Hoover Fence Company site in Reference 2 for the example.

Step 4

Note any other inputs required by the site. Obtain these inputs. The example fence will be 3 feet tall and installed in a suburban area.

Step 5

Different sites operate differently. Follow the instructions on the site to obtain the wind load. For the example, get the exposure category of B from Table 10. Then, using exposure category B, a 3-foot fence height, and a maximum wind speed of 90 mph, get the wind load value q of 11.10 pounds per square inch from Table 14.