How Deep Should a Fence Post Go?


A few posts ago we looked at how to repair existing heaved fence posts, but what if you need to construct a fence from scratch?

When it comes to digging and fitting fence posts, you don’t have to hire a professional to do so. You can easily do the job on your own, and not a lot of special expertise or equipment is really needed to get the fence up and ready. All that’s needed are a few common tools and a bit of elbow grease.

However, like most construction projects, there are certain things that you need to keep in mind so that the project is a successful one, and when it comes to erecting a fence, first and foremost you’ll need to think about the fence posts holes. The holes play an important role in ensuring that your fence is strong, will last a good few years, and be resilient to the effects of the elements. The depth of the holes is quite important, so if you’re building a fence for the first time, it’s important you achieve the right depth.

Most fences out there are made from wood, and this is what you’re probably using for your DIY fence project. If you are using 100mm x 100mm wood posts, the hole dug to accomodate it should ideally be 250mm wide. If you have access to one you can use a 250mm auger bit to do this, if not you can dig the hole manually. The standard height for a fence post should not be less than 1 metre, so as to withstand the four season climate. If you live in colder areas, you’ll need to go even deeper than this. If you don’t experience cold climate, it is still advisable that you dig a hole that is up to1 metre deep. 1 metre is recommended since it will get you past the frost line. During the winter, frost can easily heave the post from the bottom. Even if you don’t face frost issues, you’ll need to ensure the hole is deep enough.

If you’re using larger posts, 150mm x 150mm posts, you will still need to maintain the same depth of 1 metre, but the hole needs to be a bit wider, up to 300mm. Quite simply, the deeper you go into the ground, the more stable your fence will be. If you are using iron post or chain link, the diameter of the hole can be smaller, usually 200mm.

Something you need to note is that you need to contact your local utilities so that you know if there are any cables below the area you want to put up a fence – the last thing you want to do is damage those.

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