# Cinderblock Root Cellar.(engineers help please)



## Wigglesdabum

Hey guys, I am considering making a root cellar/ underground storage building sometime in the near future. I was curious if there would be any issues with me digging a hole, pouring a cement flour 30x10x10 and then laying cinder block walls, placing rebar down the holes. Then I would go back and fill them with cement. After that I need to figure out how to put a solid roof on this thing. I would like for it to be 3 or 4 feet under ground. Does anyone have any ideas?


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## rancher1913

they do that all the time. make sure you understand the forces at work. you need a grove in the cement where the center of the block will be to keep it from shearing and you need to install L shape bar into the floor that will go into every few cores or better yet every core. you will need to vibrerate the concrete as you fill the cores and make sure you have good laps on the rebar. you will also need to release the hydrolic pressures from behind the walls with some sort of drain tile. couple coats of thuro seal and a coat of black cat and its water resistant.


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## Darren

Is this going to be literally a hole in the ground or will it be dug into the side of a hill.


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## T-Bone 369

Tie the rebar in your walls into the floor slab - that's going to be you weakest spot. The best way is to pour your slab, lay the first course of block then use a hammer drill with a 1/2" bit in the cores you want to fill. The concrete will drill pretty easily especially if it is still green. Drive a peice of 1/2" rebar about 16" long into the hole with a hammer (drill your holes three or four inches deep) - you can get an epoxy filler to bond the bar in if you want but it is not required. The rebar will stick up a little above the first course but should be in the core of the second row. Lay up the rest of your courses (remembering where the cores are with the rebar then drop in a full length section from the top and slush full of concrete. As you are thinking of a solid top I would suggest that you run the rebar "wild" at the top (let it stick up above the wall a few inches) so you can then tie it into the concrete top when you pour it. 

Typically when you pour a cap like this you build a temporary floor under it, pour with wire and rebar then remove the floor after it has cured. You can use plywood or OSB - often heavy corrigated metal is used and just left. You have to build it realy strong as it has to support all the weight of the concrete while it cures - do not skimp or you'll have a real mess. I would also consider pouring the cap with a slight slope to it so water runs off instead of pooling - not much but raise your form on one side 1/2" or so. 

Be sure to do a good job of waterproofing both the wall and the top as it will wick moisture even if it is tight enough not to leak. Thoroseal is good but for where you are below grade I would go to a tar based product with a membrain and tile the permiter. I know - belt and suspenders - but it is much easier to do it when you build it than come back later if you have a problem.


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## dirtman

Build the wall on footings and then pour the floor. That will keep the base course from kicking. Also you are going to use an enormous amount of crete filling all the cores. I stack the blocks on top of each other, not a running bond. Then I rod and fill the small cores where the blocks butt up. Surface bond inside and out and you will have no problem with leakage.


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## "SPIKE"

Check this out
http://www.backwoodshome.com/forum/vb/showthread.php?t=19039

Or go down a few threads and read Coloneldad5's thread.

SPIKE


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## tarbe

[QUOTE="SPIKE";5718282]Check this out
http://www.backwoodshome.com/forum/vb/showthread.php?t=19039

Or go down a few threads and read Coloneldad5's thread.

SPIKE[/QUOTE]


That is one sweet hideout!


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## TnAndy

Temporary wood to hold concrete on roof:


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## TnAndy

[QUOTE="SPIKE";5718282]Check this out
http://www.backwoodshome.com/forum/vb/showthread.php?t=19039

Or go down a few threads and read Coloneldad5's thread.

SPIKE[/QUOTE]

The bar joists ( metal truss things ) are way overkill in a span that size. You can go 12' or more easy with simply thick enough concrete and rebar.....all that is needed is some support underneath to hold it up while it's poured and cures. I've had a 10,000lb dozer parked on top mine while backfilling.


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## "SPIKE"

tarbe said:


> That is one sweet hideout!


Thanks
SPIKE


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## "SPIKE"

TnAndy said:


> The bar joists ( metal truss things ) are way overkill in a span that size. You can go 12' or more easy with simply thick enough concrete and rebar.....all that is needed is some support underneath to hold it up while it's poured and cures. I've had a 10,000lb dozer parked on top mine while backfilling.


Hey TnAndy, Looks like you do good work!

I had the bar joist and marine grade vinyl on hand. It made for a nice clean finished ceiling. I did not have to remove any forms or supports after pouring. And they work well for supporting shelves or hanging bags of vegies from.
As far as strength goes, you are right it was overkill.

SPIKE


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## Wigglesdabum

All of this is excellent information. Thanks so much guys. Dirtman, are you saying that I should lay the slab with rebar coming out and then dry stack the bock and then fill it?
Also Dirtman... is filling just the small gaps enough to hold the pressure of the dirt pushing on it?


T-bone can i just lay 16' rebar into the slab when its poured so i can skip the drilling and hammering it in? I will be following your advice of making the roof sloped.


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## Darren

Your concrete supplier should have Q deck in stock to use as the ceiling/form for the roof slab. That eliminates the need for supporting the roof slab from below when you place the concrete. 

*The key to preventing the walls from cracking or allowing water to leak through in the future is to not back fill with clay.* Eventually, whether it is ten years or fifty years from now, the clay will destroy the integrity of the walls by cracking or collapsing them. I had a friend set in his basement family room and watch one of the block walls collapse. Ive seen tract houses built that always had wet basements during heavy rains. 

*Use geotextile and drain tile around the perimeter (holes down) and back fill with clean granular material (sand or pea gravel). Back fill within a few inches of the final ground surface before overlapping and sealing with the geotextile.*

If you build the french drain around the perimeter correctly you won't need the rebar in the block if you lay them up with mortar. If you do use the rebar in the block and it's tied into the base and roof, use grout in the cells or at the largest concrete made from pea gravel. When you use a vibrator on the concrete, do not allow it to touch the rebar.

If the root cellar is dug into the ground on all four sides, you still have to daylight the french drain. A GF bought a town house where the basement got wet because the contractor never daylighted the perimeter drain. She finally sold the place when she got transferred rather than keeping it to move back into after she was transferred back. 

Installing the french drain correctly is the simplest way to protect the walls from the earth pressure and prevent water intrusion.


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## TNHermit

When you back fill do it with Stone and Sand. dirt and clay put pressure on the walls. Sand and stone forces go down not into the wall. What generally happens when you backfill with dirt is the wall is forced in a t frost line. You can see it in old block home foundation and basements all the time. The stone and sand eliminate that. you can put a few inches of dirt on top for grass


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## T-Bone 369

Wigglesdabum said:


> T-bone can i just lay 16' rebar into the slab when its poured so i can skip the drilling and hammering it in? I will be following your advice of making the roof sloped.


Sure but be aware that if you do that you have to measure carefully so that the bar stick up into the core of the block or you'll have problems.


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## Wigglesdabum

OK so I have never worked with concrete in my life or moving soil , except digging fighting positions in the Marine Corps hah. Im going to give you a run down of what I understand so far. 

1: excavate area
2: lay french drain, line with geotextile, and a drainage pipe, holes down
3: insure its daylighted.(if its not possible to get it daylighted can I run it to a drywell?)
4: fill with pea gravel
5: lay the slab with rebar and mesh
6: insert 16' rebar vertically around the perimeter , while the slab is still wet.
7: lay the walls conventionally. 
8: insert rebar vertically (every gap for me) leave extra extended
9: fill with cement, (3000 psi) using vibrator
10: build reinforced ceiling form, bend rebar over into ceiling form
11: lay mesh , and pour cement. with 1 side elevated slightly. 
12: refill thehole with pea gravel all around the structure then cover top with dirt.


(deep breath) did I get it all hahah


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## Darren

1: excavate area
2: lay french drain, line with geotextile, and a drainage pipe, holes down
2: *line what will be the french drain with enough geotextile to extend above the depth of excavation and over lap, *install the drainage pipe, holes down
3: insure its daylighted.(if its not possible to get it daylighted can I run it to a drywell?) *Yes, just make sure that it is not subject to ground water intrusion.*
4: fill with pea gravel
5: lay the slab with rebar and mesh * I'd do the slab before doing anything related to the french drain other than excavation.*
6: insert 16' rebar vertically around the perimeter , while the slab is still wet.
7: lay the walls conventionally.
8: insert rebar vertically (every gap for me) * don't need rebar in every cell and probably not at all if the french drain is done correctly. *leave extra extended
9: fill with cement, (3000 psi) *use grout or concrete made with pea gravel.*using vibrator *You won't need to use a vibrator in the cells.*
10: build reinforced ceiling form, *(use Q deck to save money and time)* bend rebar over into ceiling form
11: lay mesh , and pour cement. with 1 side elevated slightly.
12: refill the hole with pea gravel all around the structure then, *fold geotextile over and overlap * cover top with dirt.
*13. For slabs run a stiff mix for strength. Slump around 4". In other words, you don't want a soupy mix. Soupy equals weak.*
*14. If you're working short handed ask your concrete supplier about adding Delvo to slow setup.*.
*15. Spray the concrete slabs with a curing compound after you're done finishing especially on a hot day. Keep the concrete wet for about a week to properly cure if you can't spray it with curing compound. That will help keep the floor from dusting if you don't over work the concrete. Wet burlap works fine or plastic with a garden hose underneath to occasionally add water if you don't want to use curing compound.*


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## Wigglesdabum

You have been so amazingly helpful man. I now feel like I could actually complete this job on my own. I have just a few more questions. 

-What is a slump of 4"? Do you mean make sure its at least 4 inches thick?
-Are you sure that just using pea gravel concrete is strong enough to withstand that amount of dirt? 
- With the geotextile, will I have 2 layers of geotextile with the gravel inbetween or will it go like : The concrete wall, then gravel, then one layer of geotextile? I hope you can understand my question. 
- How do you make the layer of gravel be uniform all the way up to the top? Do you pour a little then fill in some dirt around the geotextile then pour more gravel and repeat?
- last question, should I run geotextile under the bottom slab before I pour or just under and up the sides and over the top?

I cant explain how much information I have gained from you. Thank you so much.


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## Darren

The slump is a measure of how much water has been added to the concrete mix. Ask the concrete dispatcher to send you a driver that's been there for a bunch of years. Tell the driver you want a slump of around 4". He'll get it close enough.

Unless you pour reinforced concrete walls, the wrong backfill will eventually cause them to fail. The cement grout or the small aggregate (pea gravel) concrete mix you use to fill the cells can be soupy. Grout is not the same as mortar.

When you're done the geotextile will be the closest thing to the outside of the hole you dug. It will be below the drain tile and be the closest thing to the block walls. All of the granular material you use as backfill goes inside the geotextile. You should have geotextile up above the ground on the edge of the hole and coming almost as far up alongside the block wall. when you get the back fill a few inches, maybe six inches, below the surface of the ground fold and overlap the geotextile over the top of the backfill so it surrounded by the geotextile. The geotextle will surround the backfill on the bottom, the tops and all sides. that will keep soil from infiltrating and blocking the french drain long after you're gone.

Don't worry about the french drain until the cellar is finished. At that point lay the geotextile out, put the pipe in and start putting the backfill in. 

It wouldn't hurt to put a small ditch around the bottom side of the hole away from the slab draining to a sump you can use to set a sump pump to keep the hole dewatered.


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## dirtman

Wigglesdabum said:


> All of this is excellent information. Thanks so much guys. Dirtman, are you saying that I should lay the slab with rebar coming out and then dry stack the bock and then fill it?
> Also Dirtman... is filling just the small gaps enough to hold the pressure of the dirt pushing on it?
> 
> 
> T-bone can i just lay 16' rebar into the slab when its poured so i can skip the drilling and hammering it in? I will be following your advice of making the roof sloped.


The surface bonding alone will keep the walls stable. I mostly fill the small voids for added stability as I'm building up the wall. I guess I'm old school, but I always build on a reinforced footing, at least 16 inches wide and 8 inches thick with two 1/2 rerods spaced four inches in from the edge of the footing. After the wall are up then I pour the 4 inch slab When that sets up the bottom of the walls can no longer be pushed in by the backfill. If you try to build your wall on top of the slab then you will have to anchor at least stub rods into it to keep the walls from thrusting in when you back fill.


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## Wigglesdabum

Hey Dirtman, thanks for the response. I was going to use 16 inch rods into the slab so it could be supported. 

Also, I know you need a spacer for the blocks to make sure the masonry is even and all that. Is it an ok idea to do what I saw in that other thread and use rebar horizontally to reenforce and give a uniform 1/2 inch space?

Right now I am expecting to do all my own labor, and thinking this should cost me somewhere between $3500-$4000. Does that sound about right?


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## T-Bone 369

Wigglesdabum said:


> Also, I know you need a spacer for the blocks to make sure the masonry is even and all that. Is it an ok idea to do what I saw in that other thread and use rebar horizontally to reenforce and give a uniform 1/2 inch space?
> 
> QUOTE]
> 
> No - this will cause you trouble down the road. Block is designed for a 3/8" joint (8" block measures 7 5/8" tall by 15 5/8" long - add 3/8" for your bed and head joint for 8" x 16") start in your corners. Lay one block touching the corner pin with a level and a tape. Go to the next corner and figure the direction the block needs to lay - measure from the block you just layed to the pin in the next corner. Most tapes have the numbers for 16" centers marked special (think mine are in a red box) so if the 16" layout measures to the corner turn the block the long way. If it does not but it is closer to the half way between 16" centers then turn the block so the 8" face is on your wall. Lay that block, again with the level and tape then run a string on the outside of the wall from the two corners. They make a little gadget called a lineblock just for this - when you get your block pick up a couple (they are a J shaped peice of wood that has a slot to hold the string). The string should be at the top of the row on the outside. Make sure it is tight so it does not sag. Now you have a string at the correct hight and strait between the corners to lay to. Lay your row and repeat. The second row is easier as you already know the direction to turn your corners. It sounds a lot more complicated than it is - trust me a trained monkey could do it. You might look on Youtube for a video of blocklaying as a picture is worth a thousand words.
> 
> No disrespect to Dirtman but I am not a proponent of drystacking. Your footers have to be exactly flat and level to make it work well - very few professionally poured footers are that exact let alone one poured by someone without a great deal of experience. Parging a wall is not all that easy on the outside unless you overdig the hole a great deal to have room to work. I have seen it go well and look great and have seen it go wrong and have to be torn down. I agree that laying on a poured footed then coming back after the wall it layed to pour the floor is the best way to do it however it adds one more time you are going to have to call out the Ready-mix truck so adds expense. As you are going to be well below frostline either way will work well.
> 
> Don't be discouraged - it's going to be a lot of work no matter how you go about it but it's honest work and the end result will be worth it.


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## Wigglesdabum

Thank you so much. I still have a long time till I try this. I am saving all of this advice into a file so I can read it all again before I start. I now am pretty sure exactly how everything will go. I might try to find a bud who has done masonry before to help with the first row and show me how its goes and then let me go from there. Thanks again for the info


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## "SPIKE"

Wigglesdabum said:


> Hey Dirtman, thanks for the response. I was going to use 16 inch rods into the slab so it could be supported.
> 
> Also, I know you need a spacer for the blocks to make sure the masonry is even and all that. *Is it an ok idea to do what I saw in that other thread and use rebar horizontally to reenforce and give a uniform 1/2 inch space?*
> 
> Right now I am expecting to do all my own labor, and thinking this should cost me somewhere between $3500-$4000. Does that sound about right?


The block that are laid after the horizontal run of rebar are notched. So the rebar does not affect the spaceing of the block.

SPIKE


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## T-Bone 369

The only place you would use rebar laid horizontally to the block would be if your are laying bond-beam block above a door opening to create a lentel. There is a product called durawall which is a wire reinforcing product used on some jobs to increase lateral strength but mostly it is for long, tall walls. It looks somewhat like a ladder and is only 1/8" diameter. If you use rebar in a similar application it is going to be too thick (remember a standard joint is 3/8") so the block will not sit in a mortar be but rather in the rebar. Rebar has a different expansion/contraction rate than masonry so it will cause the mortar to crack letting in water. The rebar then rusts and expands even more and the wall fails. If you want to see a practical application of this look at a masonry structure above a window or dood where there is a steel lentel used. It is almost always the first place for the mortar to crack and fail. Notching the block like you pointed out will eliminate this problem but why go to all that extra work? With filled cavities you are creating a monolithic wall so there is almost no strength bennefit. 

I hope I am not comming off sounding preachy - I have seen many alternative building methods and even tried some but the fact is there is a reason that masons build walls the way we do. It works. It's not that other methods will not also work but to make what is going to be a complicated project even more difficult for someone with little masonry experience is a bad idea. Remember - KISS.


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## Darren

If you want to run a horizontal bond beam you can buy block that's U shaped that's intended for the rebar. At the height you're going you won't need horizontal rebar. 

The proper backfill and drain is all the insurance you need to protect the wall. Just remember absolutely no clay for backfill.


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## Wigglesdabum

All of this information could be the same method used for a foundation/basement for a home correct? Except obviously no roof on the basement. If I can learn the proper method here I might try to build my own home later down the road. I am only 23 right now so I have a while to learn the ins and outs. 

Understood, no rebar needed horizontally for a wall of this height.


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## Darren

Wigglesdabum said:


> All of this information could be the same method used for a foundation/basement for a home correct? Except obviously no roof on the basement. If I can learn the proper method here I might try to build my own home later down the road. I am only 23 right now so I have a while to learn the ins and outs.
> 
> Understood, no rebar needed horizontally for a wall of this height.


Correct.


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## tarbe

Wigglesdabum said:


> All of this information could be the same method used for a foundation/basement for a home correct? Except obviously no roof on the basement. If I can learn the proper method here I might try to build my own home later down the road. I am only 23 right now so I have a while to learn the ins and outs.
> 
> Understood, no rebar needed horizontally for a wall of this height.




If I knew at 23 what you are already getting fed, why.....I'd be dangerous by now!

Semper Fi Jarhead.


Tim
0351


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## kvr28

we built a small greenhouse/smoker last year that could be easily modified in the design, in the first picture you can see the side of my earth bermed house I built the same way, any questions just ask

http://thehomesteadingboards.com/2012/03/our-earth-sheltered-greenhouse/


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## BobbyB

I may have missed it, but I didnt see the actual definition for " slump"

It is how many inches the concrete spreads for one inch of height. So, a 4" slump means a pile 1" high and 4" around. The bigger the slump, the more water it has and the smaller the slump, the thicker and stiffer the concrete is. 

I have poured something close to 20,000 yards as duct bank encasement and slump was important to get equal coverage under and around stack of 4" PVC conduits up to 12 rows high and 3 wide.


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## wharton

BobbyB said:


> I may have missed it, but I didnt see the actual definition for " slump"
> 
> It is how many inches the concrete spreads for one inch of height. So, a 4" slump means a pile 1" high and 4" around. The bigger the slump, the more water it has and the smaller the slump, the thicker and stiffer the concrete is.
> 
> I have poured something close to 20,000 yards as duct bank encasement and slump was important to get equal coverage under and around stack of 4" PVC conduits up to 12 rows high and 3 wide.


Slump is determined by a very specific test using a slump cone, a flat surface, and a specific set of steps to prepare the concrete to measure. Your definition is incorrect, particularly since slumps of three and less with will not "spread". In this area you are going to get a 4-5 from a ready-mix truck, if you just order it without any special requests. For duct banks I order a 2 and vibrate it into place, for typical flat work, 4-5 is fine. Walls tend to be a little wetter, and grout is often soupy, and heading for a 8-9. Proper grouting of block cores involves rodding the core to settle the mix, and then rodding it again after the block has sucked a lot of moisture out of the mix and created a void around the mix. Rodding can be done with a scrap of rebar.


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## BobbyB

wharton said:


> Slump is determined by a very specific test using a slump cone, a flat surface, and a specific set of steps to prepare the concrete to measure. Your definition is incorrect, particularly since slumps of three and less with will not "spread". In this area you are going to get a 4-5 from a ready-mix truck, if you just order it without any special requests. For duct banks I order a 2 and vibrate it into place, for typical flat work, 4-5 is fine. Walls tend to be a little wetter, and grout is often soupy, and heading for a 8-9. Proper grouting of block cores involves rodding the core to settle the mix, and then rodding it again after the block has sucked a lot of moisture out of the mix and created a void around the mix. Rodding can be done with a scrap of rebar.


So sorry. I was under the assumption that what I had been told by the redi mix companies was correct. And the foreman I started under and my superintendent. I never thought to look up the actual definition of slump in concrete terminology. 

I stand corrected, but I will say we always poured a 5 to a 6 because we wanted it to flow around the conduits because we didnt vibrate.


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## wharton

BobbyB said:


> So sorry. I was under the assumption that what I had been told by the redi mix companies was correct. And the foreman I started under and my superintendent. I never thought to look up the actual definition of slump in concrete terminology.
> 
> I stand corrected, but I will say we always poured a 5 to a 6 because we wanted it to flow around the conduits because we didnt vibrate.


Bobby, I have to admit that using real stiff concrete in duct banks was something a very young kid. working for me, came up with. It saves an extreme amount of labor. A standard mix of 4-5 will cause pipes to float. So most banks are heavily secured with all kinds of tie wire and stakes. to do a 2 slump you place piles of concrete on top of the pipe runs, and vibrate them into the bank. It's amazing, the pipe is throughly surrounded by concrete and there is no need to stake a single thing. If you give this a shot, you have to quickly learn what a 2 looks like, without testing, and be real firm that you will be refusing anything wetter, if the batch plant gets it wrong. Good luck.


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## BobbyB

wharton said:


> Bobby, I have to admit that using real stiff concrete in duct banks was something a very young kid. working for me, came up with. It saves an extreme amount of labor. A standard mix of 4-5 will cause pipes to float. So most banks are heavily secured with all kinds of tie wire and stakes. to do a 2 slump you place piles of concrete on top of the pipe runs, and vibrate them into the bank. It's amazing, the pipe is throughly surrounded by concrete and there is no need to stake a single thing. If you give this a shot, you have to quickly learn what a 2 looks like, without testing, and be real firm that you will be refusing anything wetter, if the batch plant gets it wrong. Good luck.



After 10 years as a foreman for that company, installing several miles of duct banks , as I said some stacks 12 rows high ( or more ) with 3 inch spacings, thousands of yards of 2000 psi with grade 4 rock, I was let go due to work slow down.

But our standard procedure was for one guy to stand on the pipe close enough his feet barely got splattered and he walked the pipe as I poured. Some days we poured 300-400 feet of ditch. We werent required to stake it down, but did have to be careful not to float the ducts. 

Often I would pour it thick at the days end of the ducts so the wet mud couldnt run out and around the ends of the pipe. Occasionally we would spot drop piles down the run to help steady it while pouring. 

After a while you get so you can keep the run centered by pouring this side, then that, then down the middle an repeat. 

My flat work was limited to smaller transformer slabs and side walk section replacements, but I poured miles of duct bank. As a bonus, I have a copy of the last load ticket ever delivered by a company in San Antonio that had been in business for over 40 years, signed by me. They had sold out and on the last day, the last load came to my job.


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## elkhound

spike that sure is a nice cellar..i would love to see a few more pics if you dont mind sharing them on here with us.i am working on a cellar right now...just begining.


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## Zeet_Cranberry

Wigglesdabum...tons of good advice here. Hope you are moving forward. Just a couple of comments back to your original post....just architect pet peeves 

"Concrete" not cement (cement is an ingredient of concrete)
"Concrete Block" or "Concrete Masonry" not cinderblock. 

Ask your concrete supplier about horizontal reinforcing...use the ladder type mentioned above not rebar. Put it on every other or every third course to tie it all together.

Make sure your roof structure is on before you backfill the walls. 

Good luck!


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## Wigglesdabum

Thanks for the input guys. I haven't moved forward with this yet, it is going to be a long time before I get started. I am just planning out now what is realistic for me to do on my own once I acquire a chunk of land. This thread and the response has been more help than I could have possible imagined. Thanks again!


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