We recently had a new dog fence built around the whole of our acre of land, and all the wooden posts were set directly into the dirt – even the ones on the corners taking the tension. We could have set them in concrete, gravel or crushed rock too – but this seemed cheapest and quickest. So what are the relative merits of each method?
Concrete provides a strong foundation for wooden fence posts, but can rot them more quickly. Setting them in dirt, with or without gravel or crushed rock depending on your soil type, can help the posts last longer before going rotten. You can also use metal fence post anchors to prolong their life.
Let’s look at all these methods for setting wooden fence posts in greater detail…
Do Fence Posts Need To Be Set in Concrete?
No, fence posts don’t need to be set in concrete, and there are plenty of other ways to fix your posts if this feels a bit too permanent.
If you are using wooden posts, concrete may actually be the worst option. Why is this, because surely concrete is the most secure way of fixing a post?
Well, yes, it is at first, but the problem is that wooden posts eventually rot. You can see the problem now: the post is rotten, but it’s stuck in a concrete-filled hole. When you eventually manage to prise out the rotting wood, you’re left with a lot of empty concrete holes in your yard.
Concrete can actually hasten the rotting process, too. Because the wood and concrete expand and contract at different rates, a small “collar” will eventually form around the base of the post. This will let water seep in but it can’t seep out through the concrete, which leads to damp wood, which leads to a rotten fence post.
The solutions? Well, some gardeners swear by caulking around the post to prevent this little gao from forming in the first place. Treat the wood well first, then once everything has set in place, caulk around the base of the post. You can also try to set the concrete so it forms a low mound with the post at the top, so water gently drains downwards.
And of course, you don’t have to use wood for your fence posts. If you want the reassurance of a concrete-fixed fence without the risk of rot, use a rust-proof metal like stainless steel or aluminum, or go for low-maintenance vinyl posts.
There are plenty of other ways to set wooden fence posts, and we’ll take a look at these one at a time.
Can Fence Posts Be Set in Dirt?
Yes, they can. It seems too simple a solution; however, if you follow the correct process, you can set your fence posts straight into the dirt.
You start by digging the hole. The general rule is to dig down to a depth of one third of the post’s height. So, if you want a six foot garden fence, buy a nine foot post, then dig down three feet. The hole needs to be as close to the diameter of the post as possible.
Start by loosening the soil with a trowel, then dig down using a clam digger. You may need to also have a reciprocating saw to hand, in case you encounter tough roots. Knock rocks away with a bar, then pick them up with the clam digger. If you’re working with heavy clay soil, you may need to keep washing or wiping the digger to prevent clogging.
Hole dug, pop a flat rock, some gravel, or a piece of broken concrete in the base to use as a footing. Insert the post, checking with a level that it’s straight. You’ll need a second person to hold the post while you backfill around it, and keep checking its level.
Backfill with a mix of soil and sharp gravel, and keep tamping it down with something long and thin. When you reach the top of the hole, shovel a good amount of the mix around the base of the post, forming a mound that lets water run down.
Repeat, for every single post. Dirt-setting fence posts is a great workout.
Is it a Good Idea To Set Fence Posts in Gravel?
Gravel can be a great alternative to using concrete, and it does away with any drainage problems either underground or around the base.
However, the success of gravel as a post setting depends upon the soil. It doesn’t work in loose or sandy soils, but is ideal for heavy, clay-type dirt. It’s a good option if you live in an area that gets a lot of heavy frosts, as it makes the fence less prone to frost heaves.
The process is very similar to setting a fence post in dirt. You need to dig that one-third deep hole with your clam digger, then put a layer of gravel at its base. Put the post in the hole, make sure it’s straight (again, this is ideally a two-person job), and then backfill with more gravel. Every few inches, tamp down the gravel.
Unlike concrete, you can carry on and install the chain or rails immediately, making it a quicker job. You can also get a nice effect by growing grass right up to the base of the posts. If you want to do this, stop two inches before the ground level, and switch to using soil. You can then grass over this.
Can I set Fence Posts in Crushed Rock?
You can also use crushed rock when setting your fence posts. If you’re a keen DIYer, you’ve probably used crushed rock in at least one yard project in the past, such as placing slabs for your patio or driveway.
If you have, you’ll appreciate why it’s such a useful material for fence post installation. Like gravel, it allows for drainage around your fence post, cutting down on the risk of rapid rotting.
However, the crushed particles of rock also fuse together more readily than the larger gravel pieces. These interlocking particles form a strong foundation, closer to concrete but with drainage. In fact, it’s probably the second closest material to concrete in terms of strength, when it comes to backfilling your posts.
To use crushed rock, follow the same process as you would for larger pieces of gravel. Dig, place, fill, tamp; then fill, tamp repeat until you reach the ground level. If you’re setting a post using concrete, crushed rock can make a good drainage layer for the footing.
Are Fence Post Anchors Needed?
What is a fence post anchor? It’s simply a bracket with a spiked end, and it can make your life a whole lot easier when you’re installing your fence posts. A fence post anchor is not essential, but they certainly can help make your project that bit easier.
How do fence post anchors work? The pointed end is driven into the ground, and then the post goes into the bracket: it really is that easy. It saves all that time and effort spent digging holes, and forms a solid anchor for your posts.
First, mark out where you want your posts to go. Place the pointed end of the anchor on your mark, then check it’s straight with a level. Hit the anchor with a sledgehammer to drive in into the ground. Every few blows, stop and check the level again.
When the anchor has been fully driven in, insert the fence post into the bracket and tighten its screws. That was much easier than boring a three foot hole. Repeat, until all your posts are in place.
The good news is that now they’re in, they can stay in place for a long time. A good-quality galvanized post anchor should last for years, if not decades. You can also get anchors with circular-shaped brackets if you prefer a round post.
It’s often assumed that concrete is the best material to use for setting wooden fence posts. However, this is not necessarily the case – and is also dependant on the type of soil you have.
If you don’t want to be laboriously digging rotting wood out of cement filled holes in years to come, then setting your fence posts in the dirt may be your simplest and best option. After all – fence posts will rot at some stage (concrete actually speeds this up), so it’s easier to dig them straight out of the ground when they do.
Other alternatives such as gravel and crushed rock are a good idea too, because they increase the drainage around the base of the posts – prolonging their life.
But if you’re unsure what to do, our best bet would be to put them in the correct size holes for the diameter of the fence post, and down at the appropriate depth – straight into the earth. We did this and they’re holding up just fine. 🙂