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Do you leave plastic footers and sonotube?

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#1 foste1cc

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Posted 09 April 2018 - 11:02 PM

I just made an order at my local home improvement store for a sonotube and footer. I picked out my location and started digging a hole for my pier. Once I setup the footer and sonotube, Do I back fill with dirt around the footer and tube to help hold the weight of the cement? Or do I pour it, let it cure, then remove the plastic footer and sonotube, then fill with dirt? I guess if I back fill before I pour, I can only remove the sonotube down to ground level, and the rest stays in the ground and eventually rots. Is this a problem?



#2 DLuders

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Posted 10 April 2018 - 03:43 AM

No, it's not a problem to leave the Sonotube and its plastic "Square Foot" (like these) in the ground forever.  Although they will slightly retard the hydration (loss of water) of the concrete mix, the concrete will achieve enough strength in a few days to build upon.  You want to backfill around your footing BEFORE you pour, since you want to assure that the Sonotube doesn't shift from its vertical (plumb) position during your pour.  Try to place the concrete into the form slowly, in small "lifts", so that the aggregate does not segregate from the cement.  You want a nice, uniform mix.  


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#3 KennFromTX

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Posted 10 April 2018 - 04:40 AM

I say dig the hole throw some rebar in there along with enough sticking out of the ground (fitting the inside diameter of you sonotube) and height, fill hole half way with concrete let set then put sono over rebar fill rest of the hole up to ground level give it time to set and additional concrete into sonotube. Thats how i made my pier but used a 8" Diameter poly pipe instead of Sono tube. Then again my pier is six and a half feet in the air.  grin.gif


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#4 foste1cc

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Posted 10 April 2018 - 06:25 AM

Thanks guys. That pretty much answers my questions. I do plan on using lots of rebar.  I couldn't find anywhere local that had longer than a 4' sonotube. The next size up I could find was a 12' for special order. It will take about 3 weeks to get delivered to the store frown.gif  I will need about 8-9', being my hole will be about 4' deep and I'll need to go about 4'-5' up for my RoR.



#5 roscoe

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Posted 10 April 2018 - 08:04 AM

Same advice here..... leave whatever's below grade in place.....   

 

Danger of backfilling too soon is that you can dent the sonotube, and that if your soil is damp, it will soften the tube, leaving it weak.  I'd backfill the bigfoot so it can't go anywhere, and do the tube afterwards..... but brace the tube a lot - like 3 or 4 2x4's strapped to it, with diagonal braces leading to stakes pounded into the ground, so it doesn't decide to tip at the wrong moment.

 

Around here, real lumber yards and masonry supply houses all sell 10' tubes.....

Also, those 4' pieces usually come in bundles of 3 or 4 of slightly varying sizes that are shipped slipped into each other, you can stack a tapering form together, with the seams overlapped and securely duct-taped together.....


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#6 starcanoe

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Posted 10 April 2018 - 08:36 AM

See the other thread about "Do I need rebar in the pier".

 

The realistic answer is somewhere between 0 and a little bit. A lot will be overkill and for that matter, a bunch of rebar makes it harder to get the concrete in there and well settled, which may leave air pockets which will look bad the sonotube comes off.

 

If you are mixing yourself I think the way to go is back fill some, fill the tube with some concrete ( a bit below the back fill level)... rinse and repeat...this minimizes the chances of the concrete blowing out the tube or the soil collapsing the tube.

 

The important thing about concrete is to mix it right. Most people probably make it too runny, which is what really weakens concrete. And if you are self mixing, it might be worth the little extra bit of money to rent a mixer. Much better mix, faster, and really helpful if you have girly arms like me.

 

Also, now that I've gotten older....I buy the the 40 lb bags for 3 dollars rather than the 80 pound bags for $5. My back can't take the "savings" anymore. For that matter I am starting to look forward to the 20 pound bags for $2.


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#7 foste1cc

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Posted 10 April 2018 - 08:01 PM

I'm glad I've been doing my research before I start this. I just watched this video:

https://www.youtube....h?v=k2kd7up43sA

 

I knew there would be a lot of weight from all the cement, and since I want to go 4-5' above ground, I realized in this video I need something around the bottom of my sonotube to hold gravel to support the weight. He mentioned in his video he wasn't supposed to go higher than 3' above ground with his 12" tube. I have a 10" so I'm sure I'll need something around the base of mine as well to support the weight. I will leave the tube and footer in place and backfill to ground level, find a support for the bottom while the concrete cures, and then remove the sonotube to just ground level and leave the rest. Thanks for all the info everyone.

 

Carl


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#8 roscoe

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Posted 10 April 2018 - 09:23 PM

Good video!!  I tamp my backfill every couple of inches, which is more time-consuming, but leaves the fill a lot stiffer.

 

Note that when the guy picked up shovel-fulls of wet concrete. they stood up pretty well on his shovel, that's the firmness you are looking for.

 

A standard way to re-enforce a sonotube around here is to stand 4 2x4's up around the tube in an 'x' shape, tape them in place with some duct tape, then build two frames made of short pieces of 2x4, making a square with one pair overlapping the other pair, that fit snugly around the 2x4's, and fasten the corners together with a bunch of 3" drywall screws, or one or two screws and some 3/8 bolts,  one frame fastened a foot or so from the bottom, one a foot from the top.


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#9 macdonjh

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Posted 11 April 2018 - 08:40 AM

It's not standard practice to leave forms material in the ground, though I've never really understood why for Sonotube, which is thin.  Sonotube above grade, left exposed will start to deteriorate and it gets ugly.  I'd recommend removing that within a couple of days of pouring.  Forms material does give termites a place to hide and travel, but I'm not sure your mount is in any danger.

 

For my concrete pier, I didn't use a Bigfoot, I simply used an auger to drill down about seven feet and put Sonotube 6" below grade (to ensure a finished look for every part that would be visible) up to 42" or so above grade.  My rebar cage is 6 #3 rods held together with cyclone fence in a cylinder.  I hand mixed my concrete (eleven 80 lb sacks) because the mixer I had access to didn't do the job.  I followed the mixing instructions on the sack, the resulting mix was much closer to cookie dough than cake batter, though I didn't measure the actual slump.  I did not brace my Sonotube even though I knew I should have.  I simply watched my pier for the first four or five hours until the concrete "kicked" and adjusted plumb by hand if I noticed the Sonotube had started to lean.  I loaded the Sonotube about a half sack at a time and used a 2"x2" to pack the concrete.  I don't have much honeycombing on the outside surface, but I kind of wish I'd rented a concrete vibrator for a really smooth final finish.  Of course, I could have pointed the surface with some mortar to fill in the honeycomb, but I didn't.

 

The only place my Sonotube tried to blow out was around the two cut-outs for the conduit I ran through my pier.  The problem was the cuts disturbed the form release/ sealer of the Sonotube and allowed the cardboard to get wet and weak.  I wrapped that section with a couple of tight wraps of duct tape which proved sufficient to keep everything together until the concrete kicked.  I then used a rubbing stone to touch-up the area around the conduit penetrations after the concrete had cured and I'd removed the form.

 

When back filling, as others have said, the key is small "lifts" of a couple of inches at a time with lots of compacting between lifts.  Really, the same for placing concrete by hand in a vertical form.


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#10 roscoe

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Posted 12 April 2018 - 07:00 AM

I always call the perfect mix 'mashed potatoes' - half-way between cookie dough and cake batter.....  cookie dough's the stronger mix, but it is hard to work it into a smooth outer surface in a pier, because there is no way to trowel the surface as you would in a floor.  I usually use a stick more like an inch square to work/pack a vertical fill, and I tap on the sides of the tube as I'm going, which tends to wiggle and settle the mix a bit and work the fines out to the surface.



#11 macdonjh

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Posted 12 April 2018 - 08:15 AM

I usually use a stick more like an inch square to work/pack a vertical fill, and I tap on the sides of the tube as I'm going

When I poured, I had two choices, #3 rebar (I'd still be packing the concrete and I poured my pier more than three years ago) or a 2"x2" stake.  Wish I'd had your 1"x1"...



#12 Rusted

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Posted 13 April 2018 - 12:26 PM

I've often wondered whether placing a big, thick, paving slab under a pier or obs post footing would help to spread the load into the soil beneath it.

 

My own subsoil is clay with a high water table. Any hole or trench soon fills with water.  crazy.gif



#13 foste1cc

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Posted 13 April 2018 - 01:28 PM

My soil is also filled with clay and is very wet. Is the quickcrete 5000 necessary? Or can I use the cheap stuff?

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#14 rcdk

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Posted 14 April 2018 - 07:19 AM

Not sure I understand the necessity of forms below grade, especially for a pier.

#15 roscoe

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Posted 14 April 2018 - 07:45 AM

I've often wondered whether placing a big, thick, paving slab under a pier or obs post footing would help to spread the load into the soil beneath it.

 

My own subsoil is clay with a high water table. Any hole or trench soon fills with water.  crazy.gif

That would work, but you would want the soil below to be very firm and flat, so the paver itself didn't rock around under there.

 

The best thing, if you want a large flat footer, which will indeed make a very stable base, is to dig the hole, be sure the bottom is relatively flat, remove all the 'crumbs' of disturbed soil, and pour a 6" or so thick pad of concrete.  If the hole is dug by machine, you might want side-forms on your footer, but always...on undisturbed ground for most solidity.

 

Around here, there is a company that makes pre-cast pier parts that are each sort of the size of a 5-gallon pail, and stack, and the bottom segment is a larger disc about 24" dia and 6" thick, that you place on undisturbed soil, or crushed stone or gravel leveled and tamped down as firm as possible.    The big-box home-centers seem to be stocking, or able to order, these pier kits.

 

The huge advantage of this system is that you don't need to mix any concrete to have a very serviceable pier!

 

I try to avoid digging holes till mid-summer, because otherwise I have to pump them to work in them.


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#16 roscoe

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Posted 14 April 2018 - 07:49 AM

My soil is also filled with clay and is very wet. Is the quickcrete 5000 necessary? Or can I use the cheap stuff?

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yes, you can use the cheaper stuff.  Just don't use the product that you add to the hole dry and it absorbs moisture from the ground...it is ok for fenceposts (works great for that) but it's not real strong for structural work.  The 5000 is for more like garage floors, and is harder to work into a smooth finish.


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#17 starcanoe

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Posted 14 April 2018 - 04:15 PM

Another thing you can do is dig the hole a bit bigger than the sonotube and as mentioned above get the bottom smooth and firm. Then put the sonotube in there but with it sitting on say some solid bricks/cinder blocks. Then you do a poor to fill up the bottom and then say 8 inches give or take above the bottom of the sonotube. Let that cure for a couple of days, then finish your pour. (you'd probably want to hang your rebar in the sonotube so that it sticks down into this first pour a good bit (but you DON"T want it sticking through and into the ground).

 

This gives you a nice wide base with contact with ground, locks in the sonotube, will not blowout at the bottom, and saves you the cost of that plastic thingy. If you are worried about the sonotube getting too soggy sitting in wet concrete melt some wax and give the bottom bit a couple of good coatings..

 

Keep in mind you'd want to want to make sure the sonotube is a vertical as you can get it because you are pretty much going to lock it in place with the first pour.


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#18 Mel M

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Posted 18 April 2018 - 05:39 PM

This way is less work and stronger. Dig a 4' hole into undisturbed soil the same diameter as your 4' sonotube. In solid ground 3' might be enough. Your sonotube should only be below ground level a few inches, just enough into the hole to help hold it. Know how you are bracing your sonotube with 2x4, screws, and stakes. Maybe a dry run? Wire together 4 sticks of 1/2" or 3/8" rebar. Maybe you have 10" or larger diameter pier and want to use 5 or 6 sticks of 3/8", it doesn't matter for something this small. Pour some concrete into the undisturbed soil of the hole, no form. I'd pour two feet and then place the rebar cage in. Set your sonotube only a few inches into the hole and brace the nearly four feet that is above ground. Your rebar cage needs to be far enough below the top of your sonotube to avoid interference with any placing of bolts or later drilling you might do. If you searched out the bags of the strongest mix and cure the concrete slowly you can pour a mix that flows well. Often, stiff mixes leave voids and defeat the effort to pour stiff and strong. A pro with a vibrator can get away with it. You probably won't.

Any medium soil will make a stronger pier with this method than forms below surface with footers and backfilling.

edit: Wire a three dobies against the sides of cage at the top of your cage to help center it. Remove when needed.


Edited by Mel M, 18 April 2018 - 05:51 PM.


#19 roscoe

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Posted 19 April 2018 - 07:02 AM

in ground-freeze territory, you want your footing to be mostly or entirely below the frost line, and the pier to be smaller than that, to prevent frost action from shifting or actually lifting the pier out of the ground over time.  Those tapered plastic forms are a great solution to this, little for the frost (frozen ground) to grab. 



#20 Mel M

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Posted 19 April 2018 - 11:07 AM

in ground-freeze territory, you want your footing to be mostly or entirely below the frost line, and the pier to be smaller than that, to prevent frost action from shifting or actually lifting the pier out of the ground over time.  Those tapered plastic forms are a great solution to this, little for the frost (frozen ground) to grab. 

My frost line is 12" but I still complain about the weather.



#21 starcanoe

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Posted 19 April 2018 - 12:02 PM

My frost line is at about 8000 feet...but thats because I live in Florida.



#22 roscoe

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Posted 19 April 2018 - 07:29 PM

That's a heckuva hole to dig!  ...oh wait, do you mean up?

 

It's 4' here.... and keep in mind that snow's a good insulator, piers under buildings that have open airflow and no snow can have frost penetration a foot or two deeper than out in the open.



#23 Mel M

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Posted 19 April 2018 - 10:01 PM

That's a heckuva hole to dig!  ...oh wait, do you mean up?

 

It's 4' here.... and keep in mind that snow's a good insulator, piers under buildings that have open airflow and no snow can have frost penetration a foot or two deeper than out in the open.

I would have missed the "no snow factor."



#24 starcanoe

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Posted 20 April 2018 - 07:08 AM

That's a heckuva hole to dig!  ...oh wait, do you mean up?

 

It's 4' here.... and keep in mind that snow's a good insulator, piers under buildings that have open airflow and no snow can have frost penetration a foot or two deeper than out in the open.

 

Thats a good point.

 

Guidelines are just that ...guidelines....you kinda need to understand them and when you might need to "adjust" them.



#25 roscoe

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Posted 20 April 2018 - 08:53 AM

So true!!  A very nice deck I built back in my young and innocent days turned into a pyramid in late winter.....the customer was somewhat understanding, but the only thing worse than digging a hole is digging a hole on your hands and knees that has 300 pounds of concrete in the middle of it. for free, of course.....




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