Why concrete a fence post in the ground?

Updated March 23, 2017

There are several methods of anchoring or bedding a fence post into the ground. The method chosen should take account pf the type of fencing, posts and environment, as well as the budget for contracting or installing the fencing and fence posts yourself. If you choose concrete anchors for your fence posts, here is useful information on the process and reasons for securing your fence posts with concrete.


When installing a fence on your property remember that the only support for the structure are the fence posts. Whatever the fencing you use, the structure will have to resist a substantial wind force. The most common form of fence post anchoring is concrete. When installing the fence post, pour wet concrete into the hole around the post. If done properly, the concrete dries and sets forming a heavy anchor into the surrounding earth. The fence post embedded in the concrete is secured by the weight of this anchor.


The concrete must be poured and set correctly to anchor your fence post securely. Post holes must be dug to form an upward-facing cone shape. This shape will greatly increase the strength of the fence post and the volume of wind force your fence will be able to resist. The most common mistake when installing concrete fence post anchors is ignoring the proper anchor shape. The easiest way to address this difficulty is to buy a plastic post anchor form from your local home improvement or DIY shop.


Depending on the environment, the concrete anchor may encounter a number of stress conditions that should be considered before beginning the project. A condition that causes the greatest impact on improperly anchored posts is called "frost heave." When water in the surrounding soil begins to freeze, it expands. This puts lateral pressure on the hardened concrete fence post anchor. If the anchor was originally set in the shape of a downward facing cone, the lateral pressure will literally heave the anchor upwards. This effect will drastically reduce the structural integrity of your fence.


If you live in an area that experiences high volumes of rain or snow, understand that concrete is porous by nature and this means that in damp conditions, the concrete can absorb moisture into itself and the encased fence post. This can cause wood rot. To avoid the problem, wrap the portion of the post that will be seated in the concrete with several layers of plastic. Also, use at least 12.5 cm (5 inches) of angular cut gravel packed tightly at the base of the anchor before pouring the concrete, because this will help channel excess water away from the posts and into the surrounding soil.


Several alternatives exist for anchoring fence posts into the ground. These include anchoring posts using metal spikes, anchoring with drive anchor footings or anchoring using angular cut gravel. Using metal spikes is often the easiest, though it is only appropriate if you are installing a lightweight fence with a low clearance, as metal spike anchors have little stabilising force. Drive anchor footings are typically used in parks and in government fencing projects where maintenance and replacement will be infrequent. Using tightly packed gravel often produces an anchor that is similar in strength to a concrete anchor and it's a method you can employ yourself. Unfortunately, deeper post holes are needed and the gravel needs tight packing, so it's hard work.

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About the Author

Malik Sharrieff is a marketing and business communications professional in New Orleans. He has more than 15 years of experience in marketing, public relations and customer relationship management; over eight years of experience as an academic writer; and as an online journalist for two years.