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How to Replace a Garden Fence Post

It is often the case that problems arise with fence posts well before the rest of the fence is ready to be replaced. This is usually because the fence post has rotted away and, as it is the main support for the fence, it needs to be replaced as soon as possible.

The main reason why fence posts rot away prematurely is because they are not properly prepared or set in the first place. You see, fence posts rot due to moisture in the soil so everything you can do to reduce the effects of this should be taken when you install them. This includes using treated wood, or known rot resistant wood types, and treating the bottom of the post with a wood preservative or liquid copper naphthenate.

Another common mistake that people make when installing a fence post, is that they don’t fill at least some of the post hole with aggregate (a mix of gravel, sand, and crushed rocks) before pouring cement, and this leads to bad drainage. To be honest, using aggregate only is better to fight wood rot, but I realise cement is necessary for stability, so layering aggregate down first and topping with concrete can be a good compromise.

Now, you may be thinking this information is all great, but not so useful after the fact, but this article is going to show you how to remove the old rotted fence post and replace it with a nice shiny new one, and these tips above are there for you to implement with the new post.

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Now, this isn’t the only solution to fixing a fence post, but this is, we think, the best way to replace one. Another popular way is with the use of metal support spurs, and it is a very viable alternative, but personally, we prefer the method described below.

If you decide you’d prefer to simply repair instead of changing out for a new one, you can find that information online. You’re going to need the help of at least one person to replace a garden post so that’s the first task. Once you’ve convinced, begged, or bribed someone into providing assistance, you’re ready to start.

How to replace a garden fence post

  • The first thing you need to do is to get rid of the old fence post. Disconnect the post from the fence itself in a way that doesn’t cause too much damage to it. You might have to replace some fence panels later, but that’s an easy job and nothing to worry about. You need to dig a large semi-circular shaped hole around the old fence post that is at least as deep as the concrete base holding the post in place. It also needs to be wide enough to allow you to wiggle the concrete free of the surrounding dirt, or enough space to swing a sledgehammer in to break the concrete if needed.
  • Here’s the fun part. Grab the post and start to ‘wiggle’ it back and forth, over and over again, until the soil around the post and concrete loosens up and eventually frees it. If the wiggling of the post really isn’t working as it should, or if the post breaks off from the base due to rot, you can grab a sledgehammer and break the concrete that way. Or even use a combination of the sledgehammer and trying to shake the cement base free.
  • Once the base is free, get someone, or some people, to help you lift it out and put it to one side.  Clear the hole of any left-over concrete, wood or other debris, and you’re ready to install your new post.
  • If you haven’t already done so, follow our advice from the start of this article and treat the wood with a preservative. If you’re brushing on the preservative, wait for one coat to soak in completely before applying the next coat, and continue in this manner until you are satisfied the wood is protected.
  • Now, to avoid the same problems with rot that the last post had, we are going to fill the bottom of the post hole with aggregate, the mixture of gravel and sand that we mentioned earlier. You can buy this construction aggregate already mixed from most DIY stores.

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You’ll need to fill at least the bottom three inches of the post hole with the aggregate, but I would do more like five or six inches to be safe. This aggregate will really help out with drainage and when used in combination with the preservative, should fight off rot for years to come.

The bottom of your new fence post should be sitting in the top couple of inches of this aggregate.

  • Make sure your new post lines up in height with the old fence, and also that everything is straight with a spirit level before moving onto the next step. 
  • Next, mix your concrete and pour it into the hole. Keep pouring until it is above ground level. Using a trowel, shape the top of the concrete so that it forms a downward slope away from the fence post towards the ground. Doing this will let rainwater run off in the right direction and stop it pooling around the post and causing rot.
  • A lot of people are tempted to have the concrete below ground level to attempt to hide it for a better aesthetic, but this can actually increase the risk of the post rotting. If you really don’t like the site of the concrete above ground, just cover it with something ornamental, like large flower pots.
  • Another thing that is overlooked by many people installing fence posts is to use a silicone sealant that has been made to be used with concrete, and apply it around the fence post base, creating a nice watertight seal at ground level.

You should now have a nice, solid, and rot resistant fence post to attach your panels to. Wasn’t that hard was it?