Before you can add the privacy of a fence to your yard, it's necessary to install fence posts deep in the ground in order to provide enough support to hold up the fence during poor weather conditions, including high winds, freezing rain, sleet, and snow. If the fence posts are not installed correctly, then the entire fence is vulnerable to shifts, warping, and collapsing under its own weight, so it's important to learn how to properly set and install fence posts.
Keep in mind that you will need to dig a hole for each fence post, so it may be beneficial to rent a mechanical post hole digger to quickly and efficiently dig each post hole. Otherwise, you will need to dig each post hole with a manual post hole digger, which can greatly increase the amount of time and effort required for this project. Follow these straightforward steps to discover how to install fence posts for your new fence.
A manual post hole digger may be required if the soil is too rocky, because a powered fence post digger can cause rocks to fly out of the hole while digging. Always make sure to wear safety glasses, closed-toe shoes, and gloves to help stay safe while you work.
Before You Begin
Regardless of how wide or tall you expect your completed fence to be, make sure you have the proper permit to build a fence before you start digging: Many locales require permits before building a fence. If you live in a community with a HOA, you may have additional requirements to fulfill: Make sure you're checking all the boxes before beginning.
Equipment / Tools
- Posthole digger
- Caulk gun
- Wood preservative
- Exterior caulk
- Heartwood posts
Select Suitable Fence Post Material
Before getting started with your next fencing project, you will need to find appropriate fence post material. Keep in mind that fence posts are installed in holes that are typically deep enough for about one-third of the post to be buried. This means that a full third of the post will be exposed to moisture, insects, and temperature fluctuations in the soil, so you need to choose the right material to ensure that the fence will still be standing in a couple of years.
Opt for pressure-treated wood made of aspen, ponderosa pine, douglas fir, and other similar trees. Alternatively, you can invest in insect-resistant heartwood from western juniper, pacific yew, redwood, cedar, or white oak. Make sure that the lumber is labeled as suitable for ground contact to ensure that the material is made for burial.
Apply Wood Preservative
Even with moisture- and insect-resistant material, it's still recommended to treat the wood with a wood preservative for an added layer of protection. Use a paintbrush to apply the wood preservative to the exposed ends of the fence posts and allow about 24 hours to properly dry and cure after application.
Copper naphthenate is commonly used for this purpose, though it's important to note that wood preservatives contain powerful chemicals, so you will want to wear safety glasses, gloves, and a mask to help stay safe while working with this substance.
You can also seal the base of the post with a dry rot sealant prior to installation to further prevent rotting.
Dig the Post Hole
On average, a third of the fence post should be buried in the ground in order to provide the necessary support for the fence. This means that if the fence post is 9 feet long, then the hole will need to be just over 3 feet deep to have enough room for a gravel base and a full third of the post. In addition, the hole should be about 1 foot in diameter for a 4x4 post to ensure that there is substantial space to pour and form a concrete sleeve around the post. Repeat this process until there is one post hole for each fence post. Make sure to measure the distance between each post for a uniform appearance when the entire fence is up.
Also, keep in mind that the post needs to sit deeper than the frost line in order to prevent shifting, warping, and cracking due to frost heave in the winter. The frost line depth varies depending on your location, so make sure to determine the local frost line recommendations before proceeding. You can also check the National Weather Service's frost depth map by entering your address or zip code in order to determine how deep you should install your fence posts. It's advised to bury the post about at least 2 feet deeper than the frost line.
What Is a Frost Line?
Frost line refers to the depth at which groundwater freezes. Any structural supports that are wholly within the frost line are subjected to significant shifting forces when the ground freezes and thaws throughout the year. To help anchor the fence posts and prevent shifting, the post must be installed about 2 feet deeper than the frost line.
Add Gravel to the Hole
Use a shovel to dump 4 to 6 inches of gravel into the bottom of the hole. This will provide a solid base for the post, but will also allow water to drain away from the post instead of accumulating in the hole. Make sure to tamp down the gravel with a scrap piece of lumber so that the fence post can be installed on a firm, flat base.
Position and Brace the Post in the Hole
Lower the first post into the post hole and position it so that it sits in the center of the hole with gaps on each side to allow concrete to pour into the gap and create a solid sleeve for the post. Once in place, you can drive two stakes into the ground on opposite sides of the post so that they can secure the post between them. If necessary, add two additional stakes to help prevent the post from moving.
Repeat this process with each fence post until they are all properly positioned and braced with stakes in their respective post holes. Preparing the posts with braces ahead of time will make it easier to fill each hole with concrete and keep the fence posts in place until the concrete has time to set.
Prepare the Concrete
Concrete is relatively easy to prepare, though you will need to put in the manual effort to mix it together. A wheelbarrow is ideal for mixing the concrete due to the large base that can hold at least one full bag of concrete and the wheels, which allow you to transport the concrete to each posthole with very little effort.
Pour a full bag of concrete mix into a wheelbarrow, then add about 90 percent of the recommended amount of water. Mix the concrete solution with a shovel for several minutes, checking the consistency as you go. Slowly add more water, if necessary, until the concrete feels more like a paste.
Pour the Concrete into the Hole
Take the wheelbarrow full of concrete to the first post hole and tilt the wheelbarrow to begin pouring the concrete into the hole. Use your shovel to help direct the flow of concrete around the post, ensuring that the gap around the post is entirely filled. Proceed to the next fence post and repeat the process until the first batch of concrete is done.
You will need to mix and pour each bag of concrete one at a time. Otherwise, the excess concrete could harden and begin to set before you have time to pour it into a post hole.
Smooth the Cement
After pouring the concrete for one fence post, check the post with a level to ensure that it is properly positioned and plumb before the concrete can harden. Use a trowel to create a smooth slope that extends from about 0.5 inches about the ground to an inch below ground level to help direct the flow of running water away from the post. Repeat this process for each post.
If you simply pour the concrete and move on, then when you come back to smooth it out with the trowel, the concrete may have already set, so it's important to make sure to pour and smooth the cement before moving onto the next post. With the concrete poured and the posts plumbed, allow the concrete about three days to fully cure before beginning to build the rest of the fence.
Seal the Fence Post
After the concrete has had enough time to fully set, you will want to seal the gap between the fence post and the concrete base. Use a caulking gun equipped with an exterior sealant to carefully fill the gap at the base of the fence post. This preventative step will help to protect the fence post from pooling water and wood rot. Seal the base of each fence post the same way to keep the support structure of the fence in good condition for years to come.
Landscaping - Equipment. Canadian Centre for Occupational Health and Safety.
Guidelines for Selection and Use of Pressure-Treated Wood. United States Department of Agriculture Forest Products Laboratory.