Square Sonotube Source

[oldpops]

Hello! I'm looking to find some square Sonotube concrete forms (made of thick cardboard) but have been unable to find them locally. I've see them in a few pictures on the internet but have not had any luck in finding them to buy. Actually, I don't care who makes the form, just need a 24 inch X 24 inch (or something close). Anyone have any sources or ideas on where to get them? Thanks in advance for all your help!

 

[Blueshound_GJ]

Hello! I'm looking to find some square Sonotube concrete forms (made of thick cardboard) but have been unable to find them locally. I've see them in a few pictures on the internet but have not had any luck in finding them to buy. Actually, I don't care who makes the form, just need a 24 inch X 24 inch (or something close). Anyone have any sources or ideas on where to get them? Thanks in advance for all your help!

I think most times people just nail plywood together for square forms. But I hope you find it!

 

[larry4406]

I think most times people just nail plywood together for square forms. But I hope you find it!

Sonnotubes the cardboard rots quick. We backfill against empty tubes, get inspection and pour.

Wood forms need to be stripped before backfill (termites).

I’ve asked - don’t termites also like buried cardboard? No sane response.

 

[wssix99]

This is so crazy that I had to look it up:

A truly 'square' sonotube is impossible - so it makes sense that the product you are looking for is actually round on the outside. (That's the only way a cardboard product would keep from blowing out.)

I don't expect you will find these on the shelf at any supply. They are going to be wicked expensive and will only pay off for commercial/large scale construction. I expect the people who use them are ordering them from the manufacturer by the truckload. (Similar to other large polystyrene products such as ICF blocks.)

If you absolutely have to have it, I would contact the manufacturer and ask them for help: https://www.sonoco.com/na/products-services/industrial-products/tubes-cores

 

[cvairwerks]

How about 24x24 triple wall cardboard boxes....Just need to be a bit more cautious on filling in around them before the pour.

https://www.amazon.com/Boxes-Fast-Corrugated-Heavy-Duty-BFHD242424TW/dp/B077BWHTD3?tag=atomicindus08-20

 

[ConCretin]

I've been doing commercial/industrial concrete for almost 40 years and I've never come across this Sono-tube product. Go figure. I suspect it's more cost effective to use re-usable conventional form systems but you never know. No dog is ever too old to learn some new tricks.

 

[jack stand]

Don't underestimate the extreme forces of a 2x2' square wet column on your formwork. Even with 3/4 plywood your corners will need a lot of reinforcement. The taller it gets the more you'll need very specific methods and materials if not purpose built forms.
A form "blowout" really will ruin your day!

 

[billconner]

I agree with wssix - no rectilinear cardboard form will hold up to concrete. They'd bulge like crazy. Even 3/4" ply would require 2-by framing to keep it from bowing out.

Those with the foam are pretty cool. Kudos for finding them!

24" chimney blocks, fill, and parge?

 

[larry4406]

OP - talk to your engineer.

Determine the area of your square footer/sonnotube, convert that to a round one, round up to next size as appropriate, and ask to use that.

 

[BombShelter]

I have a feeling he wants them for above grade, maybe building columns?

 

[whateg01]

With sufficient backfill, any below grade deformation of the form would be inconsequential, wouldn't it? Somebody did say backfill before pouring

 

[The Cobbler]

probably the same reason 55 gal drums are round. anything full of flowable material wants to become round . the force on a square form needs much more material to compensate than something round.
think of the outward pressure a pop can can withstand vs the same material made square

 

[mike93lx]

With sufficient backfill, any below grade deformation of the form would be inconsequential, wouldn't it? Somebody did say backfill before pouring

Why do a square for below grade?

 

[whateg01]

Why do a square for below grade?

Because they seem to want square above grade and don't want to have to remove forms after

 

[cannuck]

Car guy here, but have designed and built a number of structures. What I have never understood (nor ever done) us run sonotube to the bottom of the bore. If you want a "friction pile" it would seem you would not want a wall of cardboard between the pile and it bore. Without a flared bottom of the hole the wall of the pile could play a very important role in load bearing. Any dirt diggers (i.e. CEs) here?

 

[billconner]

Fair point but I assume a footing and more concerned about frost gripping and lifting pier not in sonotube. I tend to think of friction piers being far far below frost.

 

[cannuck]

Fair point but I assume a footing and more concerned about frost gripping and lifting pier not in sonotube. I tend to think of friction piers being far far below frost.

I have done pilings in muskeg and they have been stable almost 50 years. Of course, they go well below frost line, but freezing can only "lift" a piling if there is water beneath it but above the frost line. I get your suggestion that expanding soil above frost line could if a REALLY good friction fit do a bit of lifting. I just haven't see that happen. Will consult my CE friend about this - but any such encounter has to first resolve the steel-in-concrete issue.

 

[MadScientist3019]

probably the same reason 55 gal drums are round. anything full of flowable material wants to become round . the force on a square form needs much more material to compensate than something round.
think of the outward pressure a pop can can withstand vs the same material made square

What everyone here is trying to identify but is not quite stating is called Hoop Stress. In a pressure vessel (which is what a concrete form becomes due to the weight of the concrete) a round structure to resist the hoop stress in it is much more efficient. Cardboard or any wood based product is best handling stresses in the direction of the wood fibers rather than relying only on the friction between the different fibers. Due to this cardboard works for "sonotube" as the hoop stress is handled more efficiently than a rectilinear form structure. That's why you never see something as weak as cardboard for any other shape of forms. https://www.engineersedge.com/material_science/hoop-stress.htm

 

[billconner]

I have done pilings in muskeg and they have been stable almost 50 years. Of course, they go well below frost line, but freezing can only "lift" a piling if there is water beneath it but above the frost line. I get your suggestion that expanding soil above frost line could if a REALLY good friction fit do a bit of lifting. I just haven't see that happen. Will consult my CE friend about this - but any such encounter has to first resolve the steel-in-concrete issue.

You could be right but I've read of frost heave by gripping the piers often, and heard it discussed by engineers. One such example:

 

[oldpops]

Thanks everybody! I should have mentioned that we live in southern California so there isn't any real danger of frost and the water table is hundreds of feet below the surface. And I should have also mentioned that I did want to start the column below the surface and come up above the surface. In any event, I have to say I am grateful for all the advice and suggestions from everyone.

 

[larry4406]

Thanks everybody! I should have mentioned that we live in southern California so there isn't any real danger of frost and the water table is hundreds of feet below the surface. And I should have also mentioned that I did want to start the column below the surface and come up above the surface. In any event, I have to say I am grateful for all the advice and suggestions from everyone.

Update your profile to include location. Classic example where location weeds out replies that don’t apply.