One of the challenges I face when building a wood fence is not only how to make it look good once it’s finished, but continuing to look good as it ages. On crucial aspect of achieving that goal is by starting with a strong foundation; the fence posts. Today I’m going to share my approach to creating a strong foundation for a wood fence.
Posts create the foundation the rest of the fence will be supported on. This is true for all fences, but especially for wood fences due to the stresses subjected to them. The weight of the fence panels themselves are supported by the posts. Wind also creates a force the posts must resist against. These stressors aren’t one off events. They occur over time and poorly built fences may not show weakness until months or even years down the road.
What allows the fence to endure these and other stressors are properly set posts. Two factors make up a properly set post; depth and diameter of the hole the post will be placed in.
Proper depth of a fence post is determined by both the height of the fence being built as well as the region it is being built. The numbers I provide here are for our region. (Note: I’m writing for a local audience so if you are building a fence outside of Louisville, KY you may want check the proper depth recommendation for your area) As a rule of thumb the farther north you go the deeper the post hole needs to be. This is due to what is called post heave. I’ll likely cover this in greater detail in a later post, but the general idea is that if the post is not set deep enough, over time it will begin to rise out of the ground as the freezing and expansion create pressure that drive the post and concrete out of the ground. Getting below the frost line will keep this from happening. This is why for a four foot tall fence I will set the posts 24″-26″ deep and for a six foot tall fence I will dig them 26″-28″ deep. Fence posts not set deep enough is the leading reason why fences fail to hold up against the stressors mentioned earlier.
Having the hole adequately round enough is equally as important as having it deep enough. For a 4×4 post an 8″ diameter is generally considered sufficient. When pulling posts out of the ground as part of a replacement or repair one of the most common errors I encounter is the post hole isn’t consistently round enough. The hole starts off at the proper diameter at ground level and begins to take a V shape the deeper it goes. This is most common when hand digging. When using a mechanical auger the hole will maintain a consistent shape throughout its depth. If you really want to maximize durability, dig a small bell shape at the bottom of the hole. I’ve pulled posts out of the ground that where straight down and ones with a bell shape formed at the bottom. The latter where far more difficult to remove. Considerably more difficult.
Following the above guidelines when digging post holes for a wood fence will give it a strong foundation from which to stand against the forces it will be subjected to. Yes, it is labor intensive and frankly, just good ol’ fashioned hard work. Like most things, the results will speak for themselves. Happy Digging!