How to Set Posts in Concrete

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Set Posts in Concrete to Repair a Damaged Mailbox

According to the United States Postal Service, there are about 52 million curbside mailboxes in the U.S. Unfortunately, many of these mailboxes are often damaged by inclement weather, reckless driving or other unexpected incidents that ultimately inhibit the successful delivery of mail. While it’s unrealistic to think that all harmful accidents to mailboxes can be prevented, homeowners can minimize the time a damaged mailbox is out of commission if they set posts in concrete.

There are many fun and creative ways to spruce up a broken down mailbox with brick, stone, paint, stain and other artistic materials, but it all starts by securing the mailbox post firmly in the ground. Without a well-grounded post, a mailbox is vulnerable to another damaging accident. QUIKRETE Fast Setting Concrete Mix doesn’t require any mixing and reaches a strength of 400 pounds per square inch in two hours making it a popular material for setting a variety of posts including mailboxes, fence posts and basketball poles.

QUIKRETE made a quick and informative video to help you set posts in concrete.  Whether you are working with mailboxes, fence posts, or basketball poles, this video shows you have to easily set posts in concrete.

Click here to use the site’s Quantity Calculator and Shopping List to determine how much concrete you will need for your project.

Set Posts in Concrete Project Instructions

The following project instructions accompany the video and provide more detail on how to set posts in concrete.  Remember, when working with cement-based products, always wear eye protection and waterproof gloves.

Step 1 – Dig post hole so diameter of the hole is three 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 to 1/2 the post height above ground (i.e., a six-foot tall fence would require a hole depth of at least two feet).

Set Posts in Concrete - Dig Hole

Image from www.quikrete.com

Step 2 – Add about six inches of QUIKRETE All-Purpose Gravel into the bottom of the hole. Then compact and level the gravel using a post or 2×4.

Set Posts in Concrete - Add QUIKCRETE Gravel

Image from www.quikrete.com

Step 3 – Set the post into the hole and attach 2×4 braces to adjacent sides of the post.

Step 4 – Use a level to position the post perfectly vertical.

Step 5 – Fill the hole with fast-setting concrete up to three to four inches below ground level.

Set Posts in Concrete - Add QUIKCRETE

Image from www.quikrete.com

Step 6 – Pour about a gallon of water per 50 lb. bag into the hole and allow the water to saturate the concrete mix.  NOTE: Mix will set hard in 20 to 40 minutes

Set Posts in Concrete - Add Water

Image from www.quikrete.com

Step 7 – Wait about four hours to begin constructing your fence or applying heavy weight to your post.

For more information on QUIKRETE projects and products visit www.quikrete.com.

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11 comments on “How to Set Posts in Concrete

    1. BARRY

      hi pros
      love your stuff.
      just a tidbit of help for some.
      i am not sure where you guys are from
      but in canada a post has to be aleast 4 ft down from ground level , or frost will heev it up out of thr grounb over time.
      as well if you are using 4×4 or any wood, make the post pointed like a v at the bottom so frost will go up the sides of the post , if it is flat on the bottom, frost has something to push on.
      i hope this helps somone.

  1. mark

    I’m curious about the 6″ depth of gravel below the post. So long as the ground isn’t mostly clay, would a minimum gravel depth of 2″ suffice for drainage, or is the 6″ just a rule of thumb to cover all climates?

    1. Billie

      You’re kidding, right? I was taught to work smarter, not harder. Heck, Quikcrete is a great product for what it’s trying to be to most people who need it. It is definite a significant shortcut and not at all lame. You say concrete will “perform” better if mixed properly or some such balderdash. If concrete holds up a mailbox or a fence adequately, then it is performing as well as practically anybody needs. Everything fails “eventually” and the vast majority of people aren’t trying to do something that will last a lifetime. Your way is fine for you, with your too much time on your hands and too much money to waste on something that doesn’t need to last very long compared to the average lifetime. Most people are going to tire of whatever it is and want to change it up.

  2. Kimber

    Pouring dry concrete in a post hole is a lame shortcut
    Concrete will perform much better if it is thoroughly mixed before placing it in the hole.
    Wood- even treated wood- posts will eventually fail when set in concrete.
    We set steel posts- round pipe or square tube in concrete
    then sleeve it with wood if desired. There are some great screws available- winged reamers- that will drill through wood then drill and tap the steel. This does take a little longer and cost a little more but you will not have to redo post in your lifetime.

    1. Joe Sainz

      Kimber – Sounds like you’ve got a great method. I’d love to show some pictures if you ever snap some of you setting some posts like this.

      Also, I’d rather see concrete properly mixed up (especially for posts that are going to last as long as yours!) – Quikrete publishes this as a method on their site for fast setting concrete.

  3. Ben

    Even though this is a relatively simple process to set posts, it is always helpful to have articles like this to ensure things are done properly. I think allowing for drainage at the bottom is an often overlooked step. I have seen cedar posts completely rot through, because there was no allowance for drainage. Some people will set posts in just sand, although you do not get the hardening effect like concrete.

  4. Bob

    We hired a contractor for the digging and filling of the post holes 2 years ago. We noticed chunks of the concrete breaking around the top of the post hole this year. Can we repair the top without having to remove, re-fill and re-post the hole?

    1. BeThePro Staff Post author

      Bob, if you are looking for an ascetic fix, the top 2” or so of concrete can be removed and re-poured. Ideally they might install an anchor or two, or some rebar into the old concrete (extending it into the new) so that the patch on top can thoroughly adhere to the old concrete. Be sure the new concrete slopes the water away – it’s possible that some water may have stood on the old concrete, and frozen/thawed to crack the old post.

      If the cracks are extending throughout the concrete depth – that is when they might need to be removed/replaced.

  5. James Bratcher

    I am getting ready to run about 500 feet of high tensile farm fence, and have read many pages of how to do this, and most all say to never pour concrete higher than 1/3 up from the bottom of the hole, as if you pour any higher, it can cause the post to bust off from the concrete, or cause the post to rot off, just saying.

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