How Deep Should I Dig a Fence Post?

A fence is a great project for a homeowner to tackle themselves. But like so many other construction related projects, the important stuff that makes for a solid job is hidden or out of sight. Fence post holes for instance. Much of the stability and strength of your fence depends on the depth and preparation of your post hole.
If a wood fence is in your future, you are likely installing 4×4 posts. A 10″ auger bit should be used, or alternatively a 10″ wide hole should be hand dug. That hole should reach about 42″ down for the typical four season climate. You may need to go a little further in colder areas, but don’t skimp and use a shallower hole no matter how warm the climate is. Basically, 42″ will get you past the frost line. When frost arrives, it can’t heave the post up from the bottom because the concrete you’ll pour in to set the post extends past it.
Even if frost is not an issue, you will still want to be around 42″ into the ground for good resistance against wind pressure and the weight of the fence.

If you are using 5×5 or 6×6 timbers as posts, keep the same depth, but make the hole wider – up to 12″. If the finished height of your fence is 8 feet or more, sink the posts another 6″ (to 48″) just for added stability.
For chain link or ornamental iron posts, you can dig or drill a hole of the same depth, but less of a diameter. A 6″ bit will do the trick, or simply a shovel width for hand digs.
When digging fence posts, be sure to contact your local utilities and find out where all of the buried cables and lines are. You don’t want to be hitting any of those as you drill or dig. Often the utility companies offer this locating service free of charge. Leave lots of time for the process in the busy months of construction.
Once you’ve dug a good hole, you can carry on with the rest of the job. And be proud of all your hard work.

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