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-   -   Taping trash bag to end of Sonotube (http://www.diychatroom.com/f105/taping-trash-bag-end-sonotube-186526/)

Clutchcargo 09-05-2013 12:30 PM

Taping trash bag to end of Sonotube
 
I read an user tip, I think it was in Fine Homebuilding magazine, where he tapes a trash bag to the bottom of the sonotube. The idea is to expand the bottom of the hole so that it's larger than the sonotube and when you start filling the tube with concrete, the bottom will fill to the entire width of the hole without spilling out and up the hole. Is this considered a good idea?
Or is there some reason that the concrete needs to be directly on earth?

GBrackins 09-05-2013 04:14 PM

that's a new one on me ..... it would only expand out if the tube is set above the bottom of the hole, or maybe my brain's not working

Clutchcargo 09-05-2013 04:18 PM

That's it exactly. As you know, here in MA we have to dig 48" down but the length on the Sonotube is 48", so to get it above grade you have to pull the tube up a few inches anyway or tape an extension on it.

GBrackins 09-05-2013 04:19 PM

you'll have to let us know how it work if you try it out

Canarywood1 09-05-2013 05:10 PM

Quote:

Originally Posted by Clutchcargo (Post 1238420)
I read an user tip, I think it was in Fine Homebuilding magazine, where he tapes a trash bag to the bottom of the sonotube. The idea is to expand the bottom of the hole so that it's larger than the sonotube and when you start filling the tube with concrete, the bottom will fill to the entire width of the hole without spilling out and up the hole. Is this considered a good idea?
Or is there some reason that the concrete needs to be directly on earth?


I doubt it would help in a shallow hole of 4 ft.depth,belling a caisson is usually done at the depth of hard pan or bed rock to add stability,and the bell is usually 3 times the size of the shaft.


http://www.google.com/imgres?imgurl=...QEwBA&dur=8913

Clutchcargo 09-05-2013 06:26 PM

I think you're right, it a real PIA to get the tube plumb in the hole where it's not sitting on the bottom. I've been scratching my head as to how to get the tube set with this method. I built a jig but it doesn't hang on to the tube tight enough without changing the shape of the tube. I think for the holes where I belled the bottom, I'm just going to throw in 6" of concrete then put the tube on top, add 4 sticks of rebar, and then fill around it before adding the rest of the concrete.

TheEplumber 09-05-2013 06:29 PM

Quote:

Originally Posted by Clutchcargo (Post 1238510)
That's it exactly. As you know, here in MA we have to dig 48" down but the length on the Sonotube is 48", so to get it above grade you have to pull the tube up a few inches anyway or tape an extension on it.

Why not get longer tube? I know it's available

SPS-1 09-05-2013 06:36 PM

1 Attachment(s)
Might be better off with a bigfoot. Gotta dig a pretty big hole though.

Clutchcargo 09-05-2013 06:36 PM

The big box stores only carry 48" tubes. I'm not sure the lumber yards would have different. I have 8 piers to pour tomorrow, so that would be 1 sacrificial tube to get all 6" above grade.
No need for big foot. I checked with the building inspector, he said even with my 10" form, my spec'ed 4000 lbs of load is nothing for the soil conditions.

TheEplumber 09-05-2013 06:44 PM

They make them longer. How do you think they pour columns and such?
check your local yards or concrete suppliers.

I suppose the bag would work too. As a youngster I worked concrete. We poured interior footing pads in corrugated cardboard forms- had to be gentle and use a stiff slump, but it worked- most of the time

Clutchcargo 09-05-2013 07:10 PM

I don't know what I was thinking, I thought it would be relatively easy to build a jig to hold these up while I poured the cement. In practice, it didn't work out that way. Oh well.

mterry 09-05-2013 07:16 PM

What if you cut part off the bottom, almost like a scalloped shape or castle-wall? That way, you have even points of contact at bottom of hole, the concrete can flow out the cutouts, and no jig needed

GBrackins 09-05-2013 08:06 PM

Quote:

Originally Posted by Clutchcargo (Post 1238564)
The big box stores only carry 48" tubes. I'm not sure the lumber yards would have different. I have 8 piers to pour tomorrow, so that would be 1 sacrificial tube to get all 6" above grade.
No need for big foot. I checked with the building inspector, he said even with my 10" form, my spec'ed 4000 lbs of load is nothing for the soil conditions.

well he'd certainly know the soils in that area better than I, but a 10" sonotube has 0.55 s.f. of bearing area. 4000 lbs load over that area requires at least 7400 psf soil bearing capacity.

Myself I would have specified a 24" Bigfoot for the 4000 lb load. If I do not have a soil test to go by I use 1500 psf as my soil bearing capacity and figure my footing based upon the load. I tend to be conservative, keeps me out of trouble.

Clutchcargo 09-05-2013 08:29 PM

I think it's (from the code book) "Slightly cemented sand" and ledge; about 8-10 tons.
All I know the first 36" took about 15 minutes, the next 6" about 20 minutes and the last 6 inches about an hour and a half with a san angelo bar to break it up and a shop vac to get it out of the hole.
The inspector wasn't concerned at all.

SPS-1 09-05-2013 08:30 PM

Quote:

Originally Posted by GBrackins (Post 1238611)
a 10" sonotube has 0.55 s.f. of bearing area. 4000 lbs load over that area requires at least 7400 psf soil bearing capacity.

No, I think they got it right. They only need 910 psf soil capacity.
.55 sq ft x 910 psf x 8 footings = 4000 pounds.


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