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What are the reasons for using something like Quikrete's Quik-tube for pouring footings for posts rather than just pouring directly into the ground with a galvanized anchor set into the top of the concrete?

One thing I read is that the tube holds moisture to allow for stronger curing, but are there other reasons aside from that or perhaps if you wanted the concrete to be above grade?

It seems like it'd be nice to have the concrete fill all voids in the dirt to provide more lean strength.

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    "The QUIK-TUBE® Building Form (No. 6922) is a ridged fiber building form tube that eliminates the need to build wood forms." It is not for "for pouring footings for posts" it's for pouring a post. If you don't live in climate 4/5, you don't, because you don't need footings. If you do, you need to dig a 5' deep hole 3' square. Now how you gonna pour a post in that hole? You don't; you pour the footing and then back fill against the tube, which "eliminates the need to build wood forms."
    – Mazura
    Nov 30, 2022 at 16:52

4 Answers 4

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There are many different reasons.

  1. You can have it above ground. Code often requires 6" above ground before wood contacts the concrete.
  2. You can calculate the volume a lot easier.
  3. You don't waste concrete on the irregular shape
  4. You can put the tube forms into an open excavation, fill around them and then pour your concrete. I did a 16' tall one.
  5. It prevents loose dirt from mixing with the concrete as the concrete is poured into the hole. If a dirt clump falls into concrete as it is poured you can have a cold join.
  6. It allows the curing of the concrete to be more controlled and result in a stronger end product.
  7. You can vibrate the concrete without it flowing into all kinds of voids and areas that aren't giving extra strength, you don't have to worry about vibrating dirt into your mix.
  8. You can lower the grade later and the concrete column would still be aesthetically pleasing.
  9. There is less wicking of moisture into the concrete
  10. You can guarantee a plumb load path to the bearing soil
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    "Code often requires 6" above ground before wood contacts the concrete." - Is that true for GC lumber?
    – MonkeyZeus
    Dec 1, 2022 at 14:03
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If the area you are in freezes, a smooth column will allow the frost to heave around it, sliding by, while a rough mess poured into a dug hole will be lifted or at least stressed by frost action as the frozen soil locks into the irregularities of the surface and then expands.

You can use reusable wooden forms rather than sonotubes for the same effect, but with a bit more labor. The tubes win because they cost less if labor isn't free.

In most cases the actual footing (below frost line) is (or should be) larger than the column on top of it, that the framing connects to, and given the price of concrete, using a form or tube to pour a smaller column on the larger footing is cost-efficient as well.

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  • A five foot deep hole, three feet square, for the footing... needs a tube on top otherwise it's a 3' square post. No footing? it's easy and it looks pretty.
    – Mazura
    Nov 30, 2022 at 16:35
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    Freezing is one of the biggest practical reasons for it. Not only do irregular shapes allow frost heaving, but also holes naturally tend to narrow as they get dug deeper (forming a wedge shape). This wedge shape makes it very easy for frost to heave the concrete in sub-freezing temps. A tube ensures a smooth surface that is not wedge shaped, which prevents the forces pushing upwards.
    – Terry
    Nov 30, 2022 at 16:57
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With a tube, you know the exact volume of concrete you need. There's less chance of making too little or too much.

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  • Not really. There's only three volumes. X number of bags, hand loaded into your car. An entire skid loaded into the back of your truck, the excess to be unloaded by a forklift and returned. Or an actual (mix onsite) cement truck. ... Mixing one or two bags on site at a time; it's always 'just one more outta do'. If there's ever more than half a bag or so wasted, the mixing guy wasn't checking with the poorer towards the end often enough. It's like $2 a bag; the getting it is the crappy part.
    – Mazura
    Nov 30, 2022 at 16:44
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    @Mazura mix onsite cement trucks are popular, but not universal. There are still some places that you order by the cubic metre, and they give you that many cubic metres. Nov 30, 2022 at 16:51
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    @Mazura Getting the volume of a cylinder isn't hard. Dec 1, 2022 at 5:52
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A tube also controls the drying rate of the concrete and gives it time to cure, where a dirt hole might drain it too quickly.Having said that, my rain-barrel platform sits on concrete poured into holes and that's up to 640 pounds per leg.

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  • 640 pounds of concrete in each leg, or each leg supports 640 pounds of water?
    – FreeMan
    Nov 29, 2022 at 18:01
  • Two 80-gallon drums. "A pint's a pound the world around " plus weigt of the barrels and platform, divided by four legs.
    – keshlam
    Nov 29, 2022 at 18:04
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    Only in the US. A normal(real) pint in the world is a pound and a quarter(1.25).
    – crip659
    Nov 29, 2022 at 19:18
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    A litre of water is 0.997 kilograms the world around. Ain't metric great? Nov 29, 2022 at 21:40
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    Blame water, not metric: commons.wikimedia.org/wiki/… (But for household purposes it's as close to 1 kg/l as to make no difference.) Nov 30, 2022 at 10:27

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