What size hole is needed for 4×4 fence post

A general rule of thumb is to dig the diameter of the hole at least 3-4 times the diameter of the post. For example, if setting 4 x 4 wood posts, dig holes 9-12″ in diameter. Posts should be centered in the hole and the posts should always have concrete under them.

Post Holes-

For example: A 4×4 post (actual size 3.5″x3. 5″) has a maximum width of just over 5″ (diagonally). Therefore, the 4×4 post will likely fit into a hole drilled by a 6″ diameter auger.

The width of the post hole should be 3 times the width of diameter of the post. For example, if you are erecting a 6 foot high fence using 4 inch fence posts, the posts need to be 6 feet above the ground. 6 divided by 3 is 2, therefore the depth of the hole required is 2 feet.

2 feet is the minimum depth that you should dig your fence post holes for. To dig the holes one-third to one-half of the post’s aboveground height, is a general formula. The deeper you dig the holes, the more stability your fence has.

When you’re installing a fence post, the amount of concrete you need will be calculated based on the diameter of your fence post and how high the post is above ground. Most fence post holes will need between 1 – 4 bags of concrete to securely hold the post in place.

Fast-setting concrete is ideal for setting posts because there’s no mixing—you simply pour the dry concrete from the bag right into the hole, then add water.

60 cubic feet. One 50-pound bag of Quikrete Fast Setting Concrete Mix yields about .375 cubic feet. For example, if you need to cover 33.333 cubic feet, using 60-pound bags of concrete, divide 33.333 cubic feet by .

Setting Fence Posts in Concrete

Concrete is the most secure material for setting fence posts, especially if you have sandy soil. Gravel may be okay with dense, clay-heavy soil, but in looser soil, concrete is the only thing that will truly keep your fence posts stuck in place.

Dig post hole so diameter of the hole is 3 times the width of the post (i.e., the hole for a 4” wood post should be about 12 inches wide). The depth of the hole should be 1/3-1/2 the post height above ground (i.e., a 6-foot tall fence would require a hole depth of at least 2 feet).

You need to level it in two directions with a 4-foot level. After getting it straight in the first direction, hold one of the braces against the post and drive a single screw to connect the brace to the post. You can then level and brace the post in the other direction and begin filling the hole.

A treated 4×4 will last 20 to 25 years in the ground if the conditions in the soil and climate are favorable. That number could increase to 40 to 75 years if you install the treated 4×4 in a cement ring rather than the soil. There are a few factors that influence how long the 4×4 can last in the ground.

Dig, align, and finish the job

Dig an 8″-diameter hole at least 6″ deeper than your area’s frost line for each 4×4 post, using a power auger, hand auger, or post-hole digger. A 6×6 post requires a 10″-diameter hole. Shovel a 6″ layer of gravel into the hole to provide drainage.

DO Employ a Base Gravel Layer

If a fence post fails without any sign of a pest infestation, it’s likely that the failure was caused by moisture that rotted the wood over time. … Once you have added gravel to a depth of three inches or so, use a piece of scrap lumber to tamp down the layer.

Simply setting the posts in concrete does create a condition that will accelerate rot in the bottom of the posts. With pressure-treated posts, the rot will be slow. … This allows any moisture that gets between the concrete and the bottom of the post to percolate through the gravel and away from the bottom of the post.