# Unconventional concrete vault pour



## Plowboy (Jul 14, 2008)

Hello,

This may be a crazy question,, But was wondering if this was possible. 

I was wondering if a person could use a 16" backhoe bucket to dig a 11' deep trench all the way around a perimeter of a proposed backporch area. Put in a foot of pea gravel with the ideal to come back lafter the pour to put in a gravel drain. Building is on a well drained hill.
Line the wall with 2" insulation board. 1/2" Rebar every 16" Pour the concrete using the dirt walls/ insulation board as forms. Then come back later and dig out the "vault". Drill holes in the walls to attach rebar into the floor. Then come back and pour the "roof" or the porch floor, tieing it into the wall rebar.

Building will be a polebarn with 1/2 of it with living quarters. Owner just wants a "vault" /stormshelter under the back porch area. No zoning, its out in the country and the dirt is hard packed red clay. 
New to the construction business, and have little or no concrete expericance..
Any advice would be appreciated.

Thanks


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## genecarp (Mar 16, 2008)

in theory it would work, its success would require concrete exp.


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## thom (Nov 3, 2006)

Using dirt for forms is nothing new, it's been done for many years. Back in the 50's a stadium was built here using that technique. Actually the stadium was an inverted bowl. The dirt form was constructed then steel and concrete applied, then the dirt removed. The building was torn down about 10 years ago. 

If it was easier/cheaper, they would build basements that way. I'd hire a competent concrete contractor. About 10 years ago I was looking at a complex concrete project. I didn't know who the right contractor for the job was so I talked to a couple of inspectors. They see all the work and know who can handle what. I got the answer I needed.


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## dlcj (Oct 1, 2007)

hmmm that approach got me rethinking about an underground shop i want to build in a hillside in my back yard. I wanted to do concrete as well but could not and did not want to buy the emmense amount of lumber it would take to form a 28x40x10 shop walls and then throw it away.So i was going to build the walls all from steel sense i got connections to get good steel for scrap price but now even that will be high! Anyway Im not a concrete man but the problems i see with that is you'll have to excavate the outside too in order to waterprof it. Will be hard to get the walls smooth. Maybe lining them with a heavy plastic would help.Also i dont know for sure if a 16" wide footing is wide enought to support that much weight. We like to pour 24" wide x12" deep footings for a wood framed house. MOST IMPORTANTLY DO NOT ENTER THAT 11' DEEP TRENCH!


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## RED HORSE 554 (Jun 26, 2008)

Use what is called stepping the foundation this will hold down the lumber cost and try to keep the lumber long enought to reuse it in the structure somewhere.Alot of the time it can be used in the knee wall built from the top of the cinder blocks or right off the footer to the box seal or building platform.


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## Bob Kovacs (May 4, 2005)

Well, let's think about this for a second:

- How do you expect to get the soil to stay vertical in an 11' deep trench?
- How would you get into the hole to install the rebar and foam (OSHA doesn't like people being put in stupidly dangerous situations like this)?
- How would you even walk along the edge of this hole without collapsing the walls?

This concept all sounds great in theory- kinda like some of the neat drawings that architects make of things that can't actually be built in the 3-dimensional world- but the chances of actually getting it constructed are pretty slim.


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## bobcaygeonjon (Aug 30, 2007)

Here in the UK we have to support the sides of any trench over 3' 3" or at least slope the sides. 
It's for a reason. If you enter that 11' trench and it collapses you will die. So please forget it.


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## RED HORSE 554 (Jun 26, 2008)

*Bob Kovacs*

you was kidding right bob go to my other post and look at a stepped down form


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## concretemasonry (Dec 1, 2006)

Without seeing the proposed plan, it is hard to give a good, accurate reply.

You are talking about a 10' or 11' wall in red clay, which will create a swimming pool around the basement.

Depending on what kind of floor you are willing to put over the basement, an engineer could save you big money even if you do not have a code or permit required.

Dirt forms are impractical and will cost you in extra concrete, since you have to dig wide enough for a footing for the cantilever wall, unless you get a creative design.

Digging everything out at once will be faster, cheaper, safer and allow the wall to be built properly. You can eliminate some of the necessary shoring and bracing. You can either rent forms or you can build with partially reinforced concrete masonry. Masonry alows you to get a footing and several courses in before a rain causes you to pump out. Around here, in the summer, the first block are laid the day of the pour or the next day. Then you are out of the mud and can grout when the wall is built.

If you get hung up on the size of the bucket or type of equipment, you could miss the bigger things.


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## RED HORSE 554 (Jun 26, 2008)

*to room*

*Unconventional concrete vault pour* the footer never gets deep enough to pin you in or cover you up as you digg down the slop you step the footer off as in moves down and build boxes to hold the step down the footer will stay at the highest levels depth and will never get to the depth of the lowest point of the footer the footer looks like a set of staires comming down under your house and if you want to use block to bring it all level you must account for the block to fit the step so to allow the block below the step to fit the next higher so that it will lay right over till it hits the next step and so on till the footer is complete and if you do a poor just form it to the step (build to fit) and whale and clip to hold as well as kickers inside and out. (still smilling) this is basic it needs no engineer) copy and past the link to a search and it will show just how we do it sir you can use knee wall to move up to your hight needed as well but insure it meets the building standrds for the outside wall structural requirments


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## gregj (Jul 31, 2006)

Plowboy, 
You might want to sub it out. 

Form Rentals around here cost about the same as ICF forms so if you don't sub it out you might compare the cost of ICFs vs form rental. If they are the same the ICFs will get you nice insulation like you wanted for free.


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## Joasis (Mar 28, 2006)

I guess I need to get my camera in and down load pictures. We just did an ICF walled basement and poured the cap Friday. 

As pointed out above, a 16 inch trench is nearly impossible....and at that depth, you would have to build the steel out of the walls and place it in....you did not list any dimensions, but this just isn't practical today with the materials we have to work with.


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## neolitic (Apr 20, 2006)

Maybe the OP has seen someone doing
slurry-wall and just missed the part 
about the slurry?
...And the expense. :whistling


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## Plowboy (Jul 14, 2008)

Thanks to all that replied, going to get a proper bid from a concrete contractor, that does basements.


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## Joasis (Mar 28, 2006)

Pictures:


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## Joasis (Mar 28, 2006)

A few more pictures. This is an current project...the basement is 24 x 24 x 8 high. The cap is 6 inches thick, the walls are BuildBlock 8 inch forms, and the beams are 10 inch I beams, splitting the span into 8's parallel with the building.


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## Winchester (Jun 29, 2008)

RED HORSE 554 said:


> you was kidding right bob go to my other post and look at a stepped down form


When I used to work for the natural gas utility I watched a real video of a guy die in a 4 foot trench being dug in the back yard of a hospital. Doctors were out in under a minute treating him and he still died.
The trench started collapsing at the bottom, took his feet out from under him partly buried him. Even that weight of dirt pretty much crushed him and he couldn't breath. Imagine an unstable 11' of trench?


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## dlcj (Oct 1, 2007)

redhorse- Dont know if your responding to the o.p. or my post and i appreciate it but i know how to do a step down footer. Do it on all most every house we build. My shop and the plowboys basement will be completly underground with flat floors and foundations so step downs do not apply. as far as icfs go, i like the idea if i where building a house but i dont need insulation in my shop and will be a waste of money for me. Looked at my hill again today and realized quik that dirt forms will not work for me cause the ground is not flat.:blink: So still looking for ideas.


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## Joasis (Mar 28, 2006)

dlcj said:


> redhorse- Dont know if your responding to the o.p. or my post and i appreciate it but i know how to do a step down footer. Do it on all most every house we build. My shop and the plowboys basement will be completly underground with flat floors and foundations so step downs do not apply. as far as icfs go, i like the idea if i where building a house but i dont need insulation in my shop and will be a waste of money for me. Looked at my hill again today and realized quik that dirt forms will not work for me cause the ground is not flat.:blink: So still looking for ideas.


ICF's provide a perfect means of forming....it isn't just the insulation. If you want bare concrete you can shave the EPS off the exposed side when you are done. I have yet to see any other cost effective ways to do this, and one more thing....I can calculate the weight per foot of wall with ICF's accurately, and then design the footing needed.


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## dlcj (Oct 1, 2007)

ok joasis, can you tell me how much concrete it'll take to pour icf forms for a building 28'x40'x10' with two 8'x10' and one 3'x7' door? All doors in front 40' exposed wall and rest waterproofed and back filled. The roof will be bar joisted and decked with steel, waterproofed then covered with 6"-12" dirt and grass. I see no purpose for concrete on the top. It just makes it heavier and then framing has to be heavier. If i go this way i will not tear off the insulation if its there allready. Ill just have to protect it with drywall plywood or steel. More money
All so i have no idea what icfs cost?


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## RED HORSE 554 (Jun 26, 2008)

*Ladwig Construction*

Can this type of system be used if a monolithic is required due to subterranean water to help it hold it out and if not how dose the cold joint get sealed to insure no penatration of water ?


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## RED HORSE 554 (Jun 26, 2008)

The footers on a stepped dow form dosent get deep enough to pin you in the ditch look at the link i pasted in the box it showes how it is done and how it dosent take much depth to achive the footer copy and past this into a search (Sorry about your co-worker)


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## Joasis (Mar 28, 2006)

dlcj said:


> ok joasis, can you tell me how much concrete it'll take to pour icf forms for a building 28'x40'x10' with two 8'x10' and one 3'x7' door? All doors in front 40' exposed wall and rest waterproofed and back filled. The roof will be bar joisted and decked with steel, waterproofed then covered with 6"-12" dirt and grass. I see no purpose for concrete on the top. It just makes it heavier and then framing has to be heavier. If i go this way i will not tear off the insulation if its there allready. Ill just have to protect it with drywall plywood or steel. More money
> All so i have no idea what icfs cost?


There is a is a calculator and a lot of information in this website. http://www.foxblocks.com/

Contractor pricing varies....but basically the cost in my area is $16 a block, and that covers 5.3 sq/ft. Then add rebar and concrete. I use BuildBlock here....same principal.


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## Bob Kovacs (May 4, 2005)

RED HORSE 554 said:


> The footers on a stepped dow form dosent get deep enough to pin you in the ditch look at the link i pasted in the box it showes how it is done and how it dosent take much depth to achive the footer copy and past this into a search (Sorry about your co-worker)


He's not talking about stepping a footing down a slope- he's talking about digging an 11' deep trench around a flat site. There's no way to create an 11' deep trench, 16" wide that you can work in, so the only option would be to do a slurry wall system with dropping in cages- the cost of that would be absurd for what the OP is talking about.


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## dlcj (Oct 1, 2007)

thanks joasis. I will figure it up and im sure i can set them myself. But i suspect it'll still be out of my budget.

Know any websites that will help me with the roof? waterproofed steel with dirt and grass on top.


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## Joasis (Mar 28, 2006)

Litedeck, another ICF product would be a far superior roof. Material costs run about $4 a sq/ft. With concrete and steel, you would be in about $8 a sq/ft for a roof that will be there for the ages, plus have an R40 or better insulation factor...do a little research, you might be surprised how far we have come in insulated concrete.


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## dlcj (Oct 1, 2007)

I'll check it out. 

To the O.P. im sorry for hijacking your thread but you got me thinking about my project again. Hope you got your questions answered.


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