Explain concrete sonotubes to me

   / Explain concrete sonotubes to me #1  

bdog

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I have a project coming up where I might use these as I will need ten piers slightly raised above ground level. What I have been reading and seen on you tube people dig a hole and shove the tube all the way in the ground and fill it up. Why?

It seems to me it would be much better to dig the hole and only shove a few inches of the tube in the hole and then fill it up so that the concrete fits and fills the hole completely and will be solid. Shoving the tube all the way in seems like it would just wind up being a wobbly weight as the tube isn稚 going to fit the hole perfectly. Concrete is heavy but it is pretty easy to wobble it around on the end of a pole if it isn稚 firmly seated in the ground.

Here is a video of what I am talking about. How to Build Deck Footings with QUIKRETE® - YouTube
 
   / Explain concrete sonotubes to me #2  
I've always thought the same thing. But its done a lot so it must work.
 
   / Explain concrete sonotubes to me #3  
The smooth surface of the tube is less likely to be grabbed and lifted by surface frost action.
 
   / Explain concrete sonotubes to me #4  
A sonotube reduces waste of concrete. Sticking only inches of the tube is counterproductive as it does not provide adequate frost heave protection and waste concrete. The amount sticking up to meet the anchor level provides a clean look, that’s important but it’s important to stick a certain amount below ground for the aforementioned reasons.
 
   / Explain concrete sonotubes to me #5  
Bdog
When I use sonotubes, they are only partially inserted in the hole.
 
   / Explain concrete sonotubes to me #6  
It all depends on your climate. In Canada we dig down four feet so that we are below the frost line. The method in that video wouldn’t do us any good because it would heave every year up down and sideways.
 
   / Explain concrete sonotubes to me #8  
bdog, where you are, you are right, there is not much point. As others have said, up here in the frosty rustbelt there are reasons to go deeper with them.

But even then, there have been a few times with non-critical structures when I have poured concrete into a cleanly augered post hole (still 4' deep, mind you) with a chunk rebar hung in the hole, and either a short chunk of sonotube or a square form for the part that shows above ground. But then, being on sand where the water all drains away and just doesn't sit in the soil in clay or silt, I can get away with that and the frost is less likely to cause trouble.

If you are on expansive clay, that might be one reason to use a deeper tube? I wonder if expansive clay down your way lifts poles the same way that frost does up here. If so, a footing that the soil has a harder time sticking to might be an advantage there, too.
 
   / Explain concrete sonotubes to me #9  
I think it's also to prevent the hole from collapsing. It could be days before you pour cement. Also, depending on the size of the tube you may need to put a footing in like a bigfoot (I use a large rock) at the bottom so the hole is going to be much larger than the diameter of the post and require backfilling.
 
   / Explain concrete sonotubes to me #10  
I have a project coming up where I might use these as I will need ten piers slightly raised above ground level. What I have been reading and seen on you tube people dig a hole and shove the tube all the way in the ground and fill it up. Why?

It seems to me it would be much better to dig the hole and only shove a few inches of the tube in the hole and then fill it up so that the concrete fits and fills the hole completely and will be solid. Shoving the tube all the way in seems like it would just wind up being a wobbly weight as the tube isn稚 going to fit the hole perfectly. Concrete is heavy but it is pretty easy to wobble it around on the end of a pole if it isn稚 firmly seated in the ground.

Here is a video of what I am talking about. How to Build Deck Footings with QUIKRETE? - YouTube
Looking at that video I wouldn't trust the concrete stability any where above ground level. The ONLY use of rebar was to get the air out. The video does tell you to put the tube sufficiently below the frost line. Apparently others didn't see that.

You should pack the hole after finishing the tube and that will prevent wobble.
 
 
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