Concrete Fence Post Dig

Depth of the Hole

• The exact depth of the hole will vary depending on the type of post you are working with. A good rule of thumb is to always dig the hole down so that you can sink at least a third of the length of the pole in the ground. For most posts this will never be more than 3 feet down or so. Holes can be dug by hand, with a gas-powered auger or with an attachment auger on the back of a tractor.

Width of the Hole

• The same "times three" rule also applies to the width of the hole, with the overall diameter being roughly three times the diameter of the post itself. The reason you need extra space is so that you have room to tamp in the gravel and eventually pour in the concrete, helping lock everything in place with a sufficient amount of weight and bracing.

Importance of Gravel

• Gravel serves more than one purpose when it comes to fence posts. First and foremost, gravel acts as drainage for water. This is vitally important for the life of the wooden post, because too much water will cause rot. Plus, water freezes in the winter, expanding and forcing the soil to buckle, which can affect the angle of the post. Gravel also works as a packing material, helping brace the post before you pour the concrete. The gravel usually fills the bottom of the hole by a few inches and is then packed around 8 inches or so up around the base of the post.

Concrete

• Although you can pour concrete all the way up to the surface of the soil, most people choose to simply pour the concrete on top of the gravel base layer until it is a few inches short of the top soil level. After the concrete begins to set up, you can then cover the top few inches of the post hole with a layer of packed soil so that it looks as though the posts were simply sunk into the earth without any other assistance.