Installing a Fence Post

Installing a fence post is fairly simple, but their are a few things to keep in mind as you get started. Below are some questions you should ask yourself along the way. Keep in mind that each situation is different, and soil conditions tend to determine what will be best. Check with your neighbors and local home improvement stores for specific advice on conditions in your area. I live in a high desert lake bed with very compact sandy soil and a 10-20″ frost line, so much of what we did is related to these conditions.

What type of wood should I use?

For most fences, treated wood is the best way to go. It is inexpensive and resistant to insects and rotting, which makes for a long lasting fence post. Another option is to use redwood posts, which tend to look a lot nicer if the post will be exposed. Redwood is pretty rot resistant naturally, but to be safe I suggest treating the portion of your post that will be underground using copper green wood preservative (this is nasty stuff so make sure to follow the ventilation and safety guidelines as instructed). We chose to do this for our golf net posts as a precaution because the thought of replacing one of our 20′ posts in 5 years didn’t excite me. Various locations have different wood options available and prices can vary as well, so check with your local home improvement store for the best options in your area.

What size post do I use?

For a standard 6′ fence a 4×4 is the typical choice. If you live in a high wind area or know the fence will have additional forces put on it, you may want to use 4×6 posts for rigidity. We live in a high wind area, and most of our neighbors used 4×4 posts for their golf nets, which sway all over the place when the winds hit, and several (including the one the previous owners installed at our house) have snapped in half. When installing our new golf net, we used 20′ 4×6 posts (with 3′ underground), and even in the highest winds, our posts are solid with very little vibration at the top.

 How large do I make the hole?

Your hole should have a 3″ gap on all sides when the post is in place, which allows for enough concrete to sturdy your post. This being said, simply add 6″ to each post dimension to determine your hole width (4×4 should have a 10″x10″ hole, and a 4×6 should have a 10″x12″ hole). Some sources say to triple your lumber dimensions, and if you have clay or softer soil, you may want to increase the size of your hole to give more surface area for the concrete.

Hole depth will depend on your ground conditions, frost line, and the above ground height of your post. For a standard 6′ fence post in most conditions, a 2′ hole should be plenty to create a sturdy structure. As a general rule, your hole should go at least just below the frost line for your area to prevent lifting. Once again, check with the garden center at your local home improvement store for conditions that are specific to your area. Also, building codes regulate this in certain areas so make sure to check those out as well.

Frost Line map for the United States

What do I use to dig a hole?

There are many options, and soil conditions play a major role in what will work best for your situation. If you don’t mind taking your time and working up a sweat, a digging bar works great to break up the soil, although in rocky conditions this is not an ideal choice (we have dug over 20 post holes of varying sizes in our yard and used the digging bar for everyone of them). If you have sandy soil and a limited amount of rocks, you can then use a Shop-Vac to extract the broken up soil or if you have thicker soil, you can use a traditional clam-shell post hole digger. If you are digging the hole “by hand” you can verify that your hole is straight and at the appropriate depth using a plumb bob.

Another option for digging is to rent or buy an auger. This will get the job done a little faster, but they can be very physically straining to operate, and can “kick back” if you hit any large rocks. Different variations require either 1 or 2 people to operate, so make sure you know what you are getting. If you choose to go this route, know how to properly use the equipment to prevent possible injury. There are other options out there, so if you are not sure which option is best for your situation, talk to someone at your local home improvement store.

How do I align and level the post?

If you are building a straight fence, start out by setting up a reference line (for this purpose it does not matter if the line is level). If you are replacing posts in the middle of an existing fence, run a line between the existing posts. For a new fence, set stakes to run your line, install your corner posts first, then run the line again from those posts.

To level the post, hold the level vertically on the side of the post and adjust the post until level. Make sure to check the level on both the side and front of the post (check The Level for specifics on using a level).

To align the post in the hole, level the post out, and check the position against your reference line. To accurately do this, shim out your line from the reference points on each side of your post, and hold a shim between your post and the reference line (this prevents you from accidentally pushing on the line while positioning the post). To adjust your post into position, you can use your digging bar to “kick” the base of the post by pivoting it on the side of your hole.

Shims help to prevent pushing on the reference line while positioning your post.

How do I hold my post in place to add concrete?

The process of adding concrete to your hole can potentially move your post out of alignment if you do not have it properly staked first. Just as you checked the level of the post in both directions, you must also stake the post in both directions. You can use two 8′ 2×4’s and a couple foundation stakes to do this. Place the 2×4 on the diagonal from the post to the ground, screw the top of the 2×4 into your post, and hammer a foundation stake into the ground next to the bottom (make sure the screw holes line up with your 2×4). Once your post is level in the direction you are currently staking, place a screw through the foundation stake into the bottom of the 2×4. Once you do this both ways, your post will be solid and ready for concrete.

What concrete should I use?

There are many different types of concrete, but most stores will carry a generic fence post mix which is intended for this purpose. Mix 1-2 bags up in a wheelbarrow by adding water until your mixture has the texture of chunky peanut butter (you can always add more water but you can’t take it away, so don’t add too much too fast). Once your mixture is ready, shovel it into your hole from all sides. With each shovelful you add, tamp the concrete all around the post to knit the concrete and remove any trapped air. Fill the hole just shy of ground level so you can top the concrete with dirt afterwards. Make sure to rinse your wheelbarrow and shovel before the concrete sets, and wipe off any concrete that may have gotten onto your post.

I hope you found this blog useful for prepping and installing your fence posts. Feel free to leave your comments or questions.

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