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Discussion Starter #1
I have never used sonotubes. We are doing a project now that requires 6 concrete piers roughly 18"x18" by 3-4' deep with weld on plates set on top of them before the concrete cures. This is for a steel building. This is not in an area with any frost heaving concerns or hurricanes etc. Not in city limits or any building codes to worry about. It is a good sized building with three sides and an open front so wind shear and uplift are concerns.

We dug the six holes with a backhoe to a depth of about 4' and as you can imagine the holes are much bigger than needed. In one dimension they are the width of the bucket which is fine but in the other they are about 4' long.

Instead of pouring a yard plus of concrete in each hole our plan was to block off half the hole with plywood, build a small form around the top to get to our desired grade and pour the pier. It will work fine but is likely more material and time comsuming.

One of the guys suggested we just use sonotubes. I have never used them but seems simple enough. Drop in hole backfill around it mark grade and cut to length then fill with concrete.

I am no engineer (obviously) but it seems to me these tubes are so smooth on the outside that they could pull out of the ground or move easily. When concrete is poured in a hole there are irregular surfaces and it more or less gets locked in place. For example try and pull out a fence post concreted in with two 80lb bags of quickcrete. It often is all a skid steer that can lift 3000 lb wants to lift it out even though it is less than 200 lbs of weight. I don't see these sonotubes locking into the ground like that or am I mistaken? Seems like you would be relying on the weight to hold it in place?
 

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Hack
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Barring the code comments, I'd say look into installing the Sonotubes onto Bigfoot bases.
They're a common item and you should be able to pick up the right sized ones almost anywhere you get your Sonotubes.
 

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Can't imagine why you would dig those with a hoe & not drill them.

Standard size auger.

You have to get the sonotube, cut to length & brace it off, then backfill holes.

In the long run it may be cheaper just to cut your losses & fill the holes with concrete.
 

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Discussion Starter #4
Can't imagine why you would dig those with a hoe & not drill them.

Standard size auger.

You have to get the sonotube, cut to length & brace it off, then backfill holes.

In the long run it may be cheaper just to cut your losses & fill the holes with concrete.
We don't have any auger bits that big. We have a skid steer with an auger but our bit is only 9". These weld on plates are 12" square. I guess we could have drilled a 9" hole to 3-4' and then hand dug an 18" square a foot deep or so on top and then built a 2x4 form around it. I didn't even think of that.
 

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I can't stamp the engineering, but in your situation, I have seen several 3"-4" holes drilled in to the sonotube and then filled with concrete.

Holes were then backfilled and compacted with a jumping jack.

I'd still defer to my original recommendation due to labor & material costs.

as a plus, you paid for some more credits from the school of hard knocks...:thumbsup:

PS= Rental yards have 18" augers....
 

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Discussion Starter #7
How about doing it the right way. ?

just saying, if your over your head trying to figure out a sonotube,
sub it out...
What is the "right way"? I assume an 18" auger but we already have the big holes now.

I am just looking for advice from others on the forum. Isn't that what it is for? All of us have different areas of expertise and can help each other out. Obviously concrete piers are not my area of specialty but I wouldn't say I am in over my head. I know I can form it up using 2x4's and plywood and be fine I was just asking if sonotubes were a good solution because it would save a lot of time but I have never used them before. I watched a guy use them on a deck before and they seem simple enough but a deck doesn't exactly have the shear and uplifts acting on it that a three sided building can. If the wind it blowing right this building is basically a giant parachute.
 

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Young-Guy Framer
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Where are you located? What type of project are you doing? And what is code in your area?

For example, here in Manitoba we can't use piers without footings or spread bore foundations (ie Bigfoots). Both bases help lock the pier in place. They're both a heck of a lot more labour intensive than just straight pier foundations because of the digging involved. Because of this, a lot of guys here are switching to ground anchors. In your case, you already likely have big enough holes to do either (footing or spread bore).

That being said, you'd have to check your building code/engineering to see what meets requirements.

In some way's I'm with jaydee. If you've never used sonotubes before, maybe you should bring someone in on this one with experience. I'm not trying to be offensive, but giving the course of action you've described so far and your idea for moving forward, I'd get the impression that you are either in over your head, or at the very least, not being as efficient as you should be.
 

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Go with the bigfoots as stated. They are plastic bases that enlarge the pier at the bottom. Compact the bottom of the hole, place the Bigfoot base, then cut sono tubes to go on top of the bigfoots. You can backfill right away and pour them after. Bigfoots are sold At home Depot and most building centers.
 

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While those new foottubes seem to me the best mousetrap yet, I would just pour six footings with verticals for the sonotubes.....you have the room, and not knowing either the weight of the structure, or the bearing capacity of the soil.....tempting fate for a few bucks seems unwise......

While your building may be fairly light, I'm on a job now where they decided to 'wing it' in regards to pier sizing, and the remedy is gonna cost someone a bundle.......
 

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By the time you figured out how to brace and mess with that sonotube, I would have poured that sucker full of concrete and been onto the next hole. And still be money ahead.
 
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