How Deep Should a Fence Post Be Buried?

Wondering how deep a fence post needs to be? Generally, you should bury your fence post at one-third to half of the height above the ground. For example, if you’re building a 6-foot fence, the underground portion of your post needs to be two to three feet. Meanwhile, the footing hole should be three times the post diameter. To keep the post hole sizes consistent, use a power auger for the digging. If you have loose soil, live in windy climate, or need to set a gate post, you’d want to dig even deeper.

Fence Post Hole Depth Guidelines

Whether you're installing a picket or panel fence post, dig your hole deep enough to accommodate one-third to one-half of the aboveground height of your fence plus 3 to 6 inches of gravel. For example, a 6-foot-tall fence should have posts buried at least 24 inches deep, plus an extra 3 inches for gravel. Here are some basic guidelines.

Post Hole Width Guidelines

The width—or diameter—of your post hole should be three times the diameter of your post. Standard post diameter varies based on the type of fence, so you’ll need to measure, but here are some common sizes.

Post Hole Depth Guidelines for Gates

Gate posts require more stability because they have to handle the weight and movement of the gate. Dig your gate post holes deep enough to accommodate one-half of the aboveground height of your fence, plus a 6-inch layer of gravel.

Fence Post Depth and Frost Lines

If you live in an area that experiences freezing temperatures, your fence will be the most stable if you position the posts below the frost line. The frost line is the depth at which groundwater freezes in the soil. The type of soil around your home, its moisture content, and average temperatures in your area all contribute to the frost line. 

When you install fence posts above the frost line, the fence can be unstable due to the freezing and thaw of water in the soil. As water freezes, it expands. As it thaws, it contracts, potentially pushing the posts out of the soil. 

Your local fence code will most likely contain information about the required fence post depth to avoid frost damage. If it doesn't, and freezes occur in your area, a safe bet is to set the posts at least 24 inches deep. 

Tips to Make Sure Fence Posts Are Set Securely

Finding the fence post depth takes a little basic math. You’ll need a calculator and some measuring tape. These tips can help:

• Measure the height of your post, then divide the total height by two or three to get a general depth.

• Burying half the pole is the sturdiest option. It’s ideal for gate posts, fences made from heavier materials, loamy or clay soil, and climates with high winds.

• You can get away with burying a third of the pole if it’s a lightweight panel post and you have a sturdy soil type like sand, sandy loam, or gravel.

• Don’t forget to add 3 to 6 inches to your measurement for a layer of gravel. The more gravel, the better the drainage. This is especially important for wood posts, which can rot in moisture.

• If you don't have experience, you should enlist a fence company near you.

Ways to Set Fence Posts

A properly installed fence post will last for several years, if not decades. Along with digging deeply enough and making the post hole the appropriate size, there are a few ways to fill the hole to increase stability.

Soil and Gravel

Pouring at least 3 inches of gravel into the bottom of the fence post hole will help improve drainage, preventing a wood post from rotting. After putting the gravel in and centering the post in the hole, fill it in with soil, tamping down as you go. When finished, you can add another 2- or 3-inch thick layer of gravel on top of the soil.

Let the soil settle for several days, tamp down again, add more if needed, and install the pickets or panels.

Concrete

Concrete is a sturdier fence post footing option than other materials. Unlike soil, concrete footings tend to settle less. However, concrete is subject to water damage, and you’d want to prevent water from seeping between the footing and the post. A simple trick is to run a bead of silicon caulk along the seam where the post and the concrete meet. Concrete costs $8 to $10 per 80-pound bag. 

Expanding Foam

Similar to concrete, expanding foam is another durable option to set your fence post in. It’s slightly less sturdy than concrete but takes much less time to set and cure. Therefore, many prefer to use expanding foam when working with lighter materials like vinyl or mesh fences. Since it’s a newer material, expanding foam costs a little more than other footing options, sitting at approximately $16 per 33-oz.

Signs Fence Posts Aren’t Buried Deep Enough

It's pretty easy to tell if a fence post isn't buried deeply enough. The post may be loose and easily moved. It may also start to lean, pulling the rest of the fence with it. Also, the bottom of your post needs to be set below the frost line. Otherwise, you will get frost heave over time and your post will eventually get pushed out of the ground after a frost due to soil contraption and movement.

Is It Possible to Reset Fence Posts?

You can reset a fence post if it wasn't installed correctly the first time. If the post was installed to the correct depth, you can fix any leaning or wobbliness by adding more soil around the post. 

Another option is to dig out around the posts and pour concrete into the hole to create a stronger base. If the posts are rotted or otherwise damaged, your best option may be to pull them up and replace them.

Installing a Fence Yourself vs. Hiring a Pro

Fence installation is not the most difficult DIY project, especially if you can find an experienced helper and live in an area that does not require a fencing permit. Typically, it’s a two-to-three-day job to build a fence, including any time you might need for post footings to set depending on the material. You can also install a no dig fence by yourself fairly easily.

However, we still recommend you to hire a pro if you’re building a taller privacy fence, or simply don’t want to deal with the time and labor. An experienced fence contractor ensures your new fence is properly installed and can handle all utility marking and permitting requirements. Generally, professional fence installation costs $1,856 to $4,750.