Post or Concrete First?

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Old 10-02-15, 12:24 PM
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Post or Concrete First?

Hey All,

I'm looking to set six schedule 40 galvanized pipe posts for a fence around my ac units and need insight into whether i should set and plumb the posts first and then infill with concrete OR pour the concrete first and then set the posts into the concrete?

Is either method more advantageous than the other? Thanks in advance and all responses are greatly appreciated.
 
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Old 10-02-15, 12:36 PM
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It's best to do them both at the same time. If you pour concrete in the hole first you might have trouble getting the post down to the correct depth. Not sure you can pour concrete around a post and not affect how it sets - you'll get it out of plumb pouring the concrete and will likely need to re adjust the height also.
 
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Old 10-02-15, 01:49 PM
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In a different thread our fencing expert stated emphatically to NOT insert the steel post into the wet concrete but he did not explain WHY that method was wrong.

My opinion is that inserting the pipe post into the wet concrete would allow a "plug" of concrete to enter the pipe from the bottom and (maybe) make a somewhat stronger joint.

If you do decide to set the post first then be sure to securely brace the post in both directions to hold it plumb while the concrete hardens. If you add the post after the concrete be sure to NOT use the fast setting concrete so you have enough time to securely brace the post in both directions before the concrete sets.
 
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Old 10-03-15, 08:22 AM
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Thanks guys...keep em coming. Still want to get a better understanding of either approach. Right now im leaning towards securing posts first and then laying in the concrete. Regarding height, im not worried about it as Im going to cut them at the height i want after and then cap. Thank u again.
 
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Old 10-03-15, 08:43 AM
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Post first, about 6 inches of stone, then concrete. The reasoning is that as the concrete cures over time a slight gap will form around the post and water will get in. The stone lets the water drain away. If the post is set in the concrete the water will be trapped and cause the bottom of the post to fail before it's time.
 
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Old 10-09-15, 06:31 AM
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Okay,

To begin with... I completely support the idea of first installing the post in the hole, back filling a little bit of soil or rock to level the post and then after the post is level in all directions and exactly where you want it,,, Then you cement the post in place.

As for the depth of the post, that would depend on why it is being placed... A fence post, a post for a clothes line, basketball court hoop... or even just for something as simple as a post to hold up a bird feeder....

My reasoning for not doing things the other way... filling the hole with cement and placing the post into the hole filled with concrete.,....

As one would do this the post may not land exactly where it was intended to be. Most concrete mixes have stones within the mix. In fact, the strongest of the mixes have stones contained within the mix. Some stones are just chips, others are full size round stones... The stones in the mix will stop the post from being in the space that the stones are taking up.... The height of the post may be obstructed or blocked on its path down, into the base...

As for the cement being pushed into the base of the post... I don't really see the advantage of having cement inside the post...
In fact, I see more a disadvantage of cement being in the bottom of the post. If water or a build up of moisture enters the top opening of the post the cement on the bottom will plug it up, stopping drainage of the water.... In colder climates the water inside the post will freeze... and the post, schedule 40 or not the post will split open like an over ripe tomato ....

And even if freezing is not a major concern drainage is ... If the water inside the post does not have a way of escape, the water will rust the post from the inside out... It may take a few years to rust out a pipe that is an eighth of an inch thick, but trust me, once it begins to rust there would be no stopping it.... and once it is gone, you would have to do the job all over again... and your second attempt would be to install it correctly. So why do it twice to install it correct the second time... Do it right the first time and it might last as long as you and I... put together.

All this is why most installers would use a stone base first, then back filling with the soil to level the post... Proper drainage is everything....

Good luck to you in your post installation project. I hope it all works out just the way you wanted it to.

Greg's Fence NJ~
 
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Old 10-09-15, 10:59 AM
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Thank you for explaining your position.
 
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