digging for concrete posts


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Old 04-09-12, 04:34 AM
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digging for concrete posts

I plan to dig and install about (4) 12" concrete posts to jack up and stabilize my front porch. I bought 12" x 4' sonic tubes but I have a question.

Should I insert the tube most of the way down into the hole, and then back fill around it?

Or can I pour the concrete into the hole and just use a tube for the last couple feet (rising about 8 or 12" above grade)?

It seems like the second method would give me a more stable post by not having to tamp dirt around the tube.

What do you think, and do you have any advice for the job?
 

Last edited by Pilot Dane; 04-09-12 at 04:54 AM.
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Old 04-09-12, 09:40 AM
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The question is weather it is OK to pour into a hole without using a sonotube? Any comments or advice?
 
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Old 04-09-12, 09:46 AM
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Not an expert but I'd think it be ok to not sink the sonotube all the way down.
 
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Old 04-09-12, 09:59 AM
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Run a string line for the proper elevation for the top of the posts. - Are you sure you need 12" wood posts?

Insert the 12" Sonotubes to the proper elevation and line. Vertical rebars optional.

Dump in some rock and sand and compact somewhat, while maintaining line and elevation and brace lightly.

Fill the tube with concrete and insert a galvanized Simpson connector to the desired elevation.

Wait several days to cure, then insert and connect the posts. Cut off the exposed Sonotube portions for desired appearance.

Dick
 
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Old 04-09-12, 11:57 AM
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This is my plan-

Dig by hand aprox 12" diameter hole, 4 feet deep. Cut tubes in half, so they are 24" long.

Widen hole at top so I can snugly insert the 2' tube, leaving about a foot above grade.

Dump in a shovel or two of coarse gravel for drainage.

Mix and pour up to the top of tube, inserting 3 rebars as I go.

Strike the top level and let it cure.

I will use these footing to jack up my porch, then install perminant posts on top of these footings.

Should I try to insert anchors while wet, or drill and anchor after the fact?
 
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Old 04-09-12, 12:31 PM
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The reason for the Simpson connector plates is to allow embedment into the fresh concrete, but you can use a J-bolts also. How do you propose to control the top elevation of the 12"x24" long Sonotube in the 4' deep hole? Being "snug" is difficult as you fill and pour and you may end up pulling the tubes up as you go to maintain a uniform elevation of the piers.

The shovel or two of coarse "gravel" that will be in contact with the natural soil or concrete does little.

Rebars are good, but not necessary for such a wide and short concrete pour. A chunk of concrete 4' long and 1 foot wide does not have lateral load problems

If the piers are poured to a controlled elevation with embedded plates, there is no need for drilling and epoxy embedment.

If you do not control the level top foundation elevations, you will have to cut individual posts to fit.

Dick
 
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Old 04-09-12, 12:55 PM
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OK, but how hard do I need to back fill and tamp around the tube to keep it from shifting? Seems like the pier would be more solidly located if it didn't have 'loose' dirt surrounding it.

I thought I would dig my hole slightly smaller than the tube, allowing the tube to rest on a shoulder of dirt.


These are going to be used to jack up and re support the existing porch. I am using a 6x6 post, not 12" post.
 
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Old 04-09-12, 01:44 PM
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I assumed you were using gravel and not just"dirt" around the Sonotube, since gravel would be more stable and easier to compact. "Dirt" is worth nothing when it comes to stability near ground level.

What ever you want to do is O.K. as long as you can control and maintain the elevation of the tops of the Sonotubes before during and after pouring/placing the concrete. If not you just have to cut each 6x6 to the correct length for reach pier.

Unless you have a large deck with tall posts, the lateral load and stability in not a problem.

Dick
 
 

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