FAQ: How Many Bags Of Concrete Needed For Fence Posts?

How do you calculate concrete for fence posts?

Example Fence Post Concrete Calculation

  1. Calculate the post volume. Change post diameter to feet: 3.5” / 12 = 0.2917′ Find radius (½ of the diameter):
  2. Calculate the hole volume. Hole radius (3x post radius): 3 x 0.1458′ = 0.4374′
  3. Calculate concrete volume. Hole volume – post volume: 1.2026 – 0.1336 = 1.069 cubic ft.

Is 2 feet deep enough for fence posts?

Project Instructions



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).

How many posts will a 20kg bag of Postcrete do?

“Usually one bag of postcrete per post is enough, however you can use a two bags per post if you feel this is needed. The instructions are on the bag.”

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How much sand and cement do I need for fence posts?

In terms of the ratio to use for a concreting fence posts, the best mix is a mix of 1:2:4 (1 cement, 2 sand, 4 aggregate). Concrete is always best mixed using a cement mixer to ensure it’s even, but if you only need to mix a little, hand mixing is ok (see mixing concrete project above for tips on how to do this).

Should I use concrete for fence posts?

Concrete is the most secure material for setting fence posts, especially if you have sandy soil. Using premixed concrete rather than dry concrete will ensure ultimate security. While concrete is sturdy, it lacks the drainage of gravel and can trap moisture, ultimately leading to rot.

How many bags of concrete do I need for a 10×20 slab?

A 60-pound bag yields. 017 cubic yards, and an 80-pound bag yields. 022 cubic yards. For a 10 x 10 slab, you would need 77 60-pound bags or 60 80-pound bags.

How deep should a 8 foot fence post be?

In general, holes should be at least 3 feet deep for posts that extend 8 feet or more above ground level. Posts that extend 6 feet above ground level should have holes at least 2 1/2 feet deep.

Will wooden posts rot in concrete?

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. The concrete at the top should be sloped away from the post to grade level to avoid water pooling around the base.

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Should I use 4×4 or 6×6 fence posts?

4×4 is perfect for these very standard fence dimensions. Normally 4×6 or 6×6 are needed for gates or extreme wind loads.

Is Postcrete better than concrete?

Concrete spurs are ideal for repairing the posts, use postcrete, sets pretty quick and you should only need 1 bag per hole. Concrete blocks will be the easiest for sitting the shed bearers on, or split them in half.

What size hole does a bag of Postcrete fill?

Just over one bag per hole should be sufficient, blue circle postcrete suggest 1 bag will fill a 8 x 30 inch hole with a 4×4 post. You’re dimensions are slightly bigger than that so better to be safe than sorry and have a bit extra.

How much water do you put in a bag of Postcrete?

Fill hole 1/3 full with water, add postcrete, add extra water on top. Stays workable just long enough to slope away from post.

What is the best concrete for fence posts?

Fast-setting concrete is ideal for installing fence posts since it doesn’t need to be mixed in a bucket or a wheelbarrow. Once you’ve finished digging your post holes, add about three to four inches of gravel into the bottom and compact it using a post or a 2×4.

How do you keep fence posts from rotting in concrete?

Caulk Around the Fence Post Base



Apply high-quality exterior acrylic latex caulk, or silicone specifically designed to adhere to concrete, at the base of the post.

How do I keep my post level while concrete dries?

Fill the hole up to a depth of 8 inches from ground level with 1/2-inch drainage gravel. Use rough-cut gravel with sharp edges. It will hold the post better than smooth rock.

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