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Discussion Starter · #1 ·
What’s the consensus for post setting?

We used to dig a 3 - 4ft deep hole, stick the post in, and fill it to the top with bags of dry concrete and keep on working.

Now it’s my understanding to put 6” of gravel on the bottom and do as described above.

But

Someone else is telling me to put a bag of concrete in the bottom, put the post in, and fill to the surface with gravel.

Others are saying, don’t put a wood post in the ground, pour a concrete footer and set your post on it at grade.

This will be 6 - 6x6’s for a 10x20 shed foundation.

So, what is the preferred method for setting posts these days?


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retired framer
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Posts rot at ground level and I have never understood the worry about the bottom.
Save that for fences and pour the concrete and set in a post saddle. Just a little deeper than your local frost depth.
 

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For better weight bearing put the concrete in the bottom of a hole larger than the post to spread the load. I don’t put concrete around the post. There is no added weight bearing capacity by having a donut of concrete around the post so the post can push through. In freezing climates if you fill the hole with concrete and there is taper in the hole, frost will expand the ground and pop the concrete up out of the ground. Treated wood shrinks, if it is surrounded with concrete a space results. That space fills with water and the post, even treated wood, will prematurely rot. The same will happen if you backfill with gravel. I put a pad in the bottom, put the post on it and backfill with dirt, tamping it every 6 inches or so. If you need more uplift resistance, dig the hole bigger, attach a cross piece near the bottom of the pole, then continue. The cross piece will require moving a lot of dirt to move up. This is from 50 years of seeing what happens with all the methods you can think of.
Or you can pour a pier and put the post on it. If in a freezing climate no taper. Then deal with attaching the post by various means.
 
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Actually, since posts will rot at ground level, the best solution I have seen is to take advantage of the slump. Slump being an early measure of concrete strength.
So you taper the concrete fill up the posts to the point where the slump will no longer hold. This makes rain etc slide off the posts.
 

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I'll share my experience with 6 X 6 ptw buried in the ground.
When ptw first came on the scene, it was promoted as safe to install in the ground at least by some contractors.
About 6 years after my deck was built, I noticed that the color of the wood at the base where it goes into the concrete driveway was different. Right away, I suspected dry rot. So I poked at it with a screwdriver and the tip went in about 1/2 to 5/8 inch. I immediantly called a contractor to replace both 6 X 6 posts. This time, the contractor installed a pier with a metal bracket to secure the post.
 

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retired framer
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I'll share my experience with 6 X 6 ptw buried in the ground.
When ptw first came on the scene, it was promoted as safe to install in the ground at least by some contractors.
About 6 years after my deck was built, I noticed that the color of the wood at the base where it goes into the concrete driveway was different. Right away, I suspected dry rot. So I poked at it with a screwdriver and the tip went in about 1/2 to 5/8 inch. I immediantly called a contractor to replace both 6 X 6 posts. This time, the contractor installed a pier with a metal bracket to secure the post.
They do better if you wrap them at ground level like they do with wood telephone poles
 

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Big Dog
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I bought the house in 1996. At the time the inspector determined the deck was about 2-years-old. (The previous owner could not be asked about this as he had passed away prior to the house going up for sale.)

The deck was clearly not professionally built. This was evident in that the posts were tripled 2x4s nailed together, the decking was a hodgepodge of 1x4s secured with common nails and railing system clearly made up of scrap 2x4s.

I wanted to rebuild the deck for the longest while but priorities and other obligations forced me to postpone that.

In 2017, I rebuilt the deck. When I pulled the old posts out, I found they were not in concrete. After cutting away the joists and beams, I could lift the posts out by simply moving them back and forth and side to side a couple of times and then pulling straight up.

As I was planning to bury the new posts, I was interested in the rot rate and therefore carefully examined the section that had been buried. I was surprised to find that even after 21 years buried in clay based soil, it had not rotted to a significant degree. Their was some surface deterioration but it only went down about 1/4-inch from the wood surface. I cut the post about 8-inches from the bottom which confirmed that aside from the surface area, the wood was still pretty solid.

Code called for 6x6 posts on the new deck. I dug the holes down to about 30-inches to insure I was below the frost line. I then put down about 6-inches of gravel and solidly tamped it down. The posts was centered and plumbed in the hole and Sakrete Fast Setting Concrete Mix added. This concrete mix does not require mixing and the posts can be worked on in about an hour after the pour is completed. It is important to note that the posts I used are rated for ground contact.

You can click on the link below to see the whole build.
 

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Discussion Starter · #15 · (Edited)
Okay. So, I’m not building in flat ground, with the back side of the shed being 2 - 3ft below grade. Anyway, if I chose to use sonotubes and concrete, would I just pour each of the 6 sonotube footings to a few inches above grade, add a 6x6 saddle, and put my posts on there, or, measure and pour each sonotube level to where I want my beams, and rest the beams directly on the concrete forms.....using a saddle of some sort, and not use any 6x6 posts?

Also. What would I do at the front of the shed where it’s at grade? I


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retired framer
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The holes always want to be a frost depth where you are.

You can have the front framing sit in smaller saddle, the back can be either or.
Sono tubes can cause trouble too.

If we have a lot of weight we dig a bigger hole for a footing and come up with the sono tube and the footing will hole the pier straight and plumb.
If you just put dirt in the hole it fits tight to undisturbed soil and stays in place but any rough edges in the concrete can be caught by frost and lifted.

If you can you dig a smaller hole and then buy a tube that is just a bit bigger and fit the hole to the tube so you leave as much undisturbed soil as you can around it. If you can enlarge the hole at the bottom and lift the tube off the bottom about 6" you get a bigger foot print for the weight.

Or rent an auger
https://www.homedepot.com/p/Powerma...PIPHorizontal1_rr-_-202978107-_-202532639-_-N
 

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Discussion Starter · #18 ·
Since everyone is against posts in the ground, I’m thinking about sonotubes. One side, left, is level ground. I think I’ll put the beams directly on them with a bracket. The right side I’ll probably sonotube to a few inches above ground level, and then posts to level. Notch the posts for the beams.
Would two, 2x10x20’s, PT, on each side suffice for my beams for a 10x20 shed? Joists would be 9’6”, probably 2x8’s.
Shed will hold a toro lawn tractor, small atv, small trailer for the atv, and miscellaneous BS.


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retired framer
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Since everyone is against posts in the ground, I’m thinking about sonotubes. One side, left, is level ground. I think I’ll put the beams directly on them with a bracket. The right side I’ll probably sonotube to a few inches above ground level, and then posts to level. Notch the posts for the beams.
Would two, 2x10x20’s, PT, on each side suffice for my beams for a 10x20 shed? Joists would be 9’6”, probably 2x8’s.
Shed will hold a toro lawn tractor, small atv, small trailer for the atv, and miscellaneous BS.


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put a third post at 10 ft on the sides 20 wouldn't work with any size beam.
 
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