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We have a chain link fence around our tennis court with a shade cover installed that covers the chain link. A high wind came along that bent the posts over. How can we tell whether the damage was done by the wind or shabby installation?
Most 10-12' high tennis court fences with no wind shield can withstand gusts exceeding 50 mph. The problem is when a wind or shade cover is hung on the fence, you have in a sense built a giant sail. The constant blowing of the wind will lean a normal chain link fence without a gust of 50 mph.
If you intended to hang the cover on the fence from the beginning, it should have been built much stronger than normal. In addition some consideration must be given to wind slits. These are spaces in your cover that allow wind to pass through. A vertical space every 10-20' along the fence helps. Leaving a space of 1-2' under the cover allows another place for the wind to escape through your structure. Installing two layers of cover horizontally with a 1' space between them, say 7' above the ground is another type of wind slit. Using a type of material that is a little porous will allow for some wind to pass through also.
The posts for a 10-12' high chain link fence should be no smaller than 2 1/2" O.D. with a heavy wall of HF40 pipe or sch. 40. This is without consideration of adding wind catching surfaces. The normal post spacing for a normal chain link is no more than 10'.
If planning to add a solid shade or wind cover, including any sort of privacy slats, the post diameters should be increased to a minimum of 3" O.D. and the post spacing should be no more than 8' apart. Solid fences in high wind areas could require 4" O.D. posts with even closer spacing, like 6' apart, but this is unusual.
In addition to this, the concrete footers and depths should be increased. Footers should be a minimum of three times the diameter of the pipe used. We commonly use a minimum 12" diameter footer even for posts less than 4" O.D. The depth of a normal footer should be 36" in most areas, but 42" in this case. The post need not go to the bottom of the footer, but should be no less than 6" from the bottom. Where extreme high winds are expected, 48" deep footers are not unrealistic.
To understand why your fence failed, you must first see if the preceding guidelines were followed. The next thing is to examine the damage. Did the footers lean with the post and the posts did not really bend? If so, the post did not fail, the footer did. Did the footer remain stable and the post bent at or near the footer top. If so, this indicates post failure. Perhaps the posts were spaced too far apart or their diameter or wall thickness were too small.
Did you tell the contractor that you intended to install a solid cover on the fence? It is not likely a contractor would install a suitable fence for this purpose, unless you told him your intentions. It would be the same principle, if you had tied your prize breeding bull to a fence post and expected the post not to move.
Another reality is that the wind may have gotten the best of your fence due to no other reason than what we call an "Act of God". Your insurance should cover this, if you have the proper type.
Years ago we installed a 6' high solid wood fence that later was in the direct path of a tornado. Remarkably the tornado tore all the pickets and 2 x 4 rails off the posts leaving 4 x 4 posts still standing in their 10" diameter x 36" deep footers. In addition these post footers had been "belled" at the bottom. Only a few posts were broken and needed replaced. The rest were used in repairing the fence. An unusual occurrence, perhaps, but true enough. In this case the boards went flying before the posts. The repaired fence is still standing today in Newton Falls, Ohio. (Downtown Newton Falls was all but destroyed that day). Short of a tornado, a good fence should withstand most storms, if it is built properly.
MORE INFORMATION: How To Build Chain Link Fence