OT: pouring concrete under a house?

OT: pouring concrete under a house?

Kolea
Kolea

February 12th, 2012, 8:27 pm #1

Hey,

I volunteer with Habitat for Humanity, and the current house that we're working on needs to be jacked up a little bit since its sagging in the middle. The foreman wants to pour back some concrete around the current concrete footings that are under there, since there has been mild-to-considerate erosion under the footings and they're no longer fully sitting on the ground.

We've got these form boxes that we're going to put around the footings and nail together. The problem is getting the concrete into the forms. There are three rows of four footings and almost all of them need poured back.

Things we're considering but not fully bought into yet:
We've tossed around making a mini concrete pump out of some hose and lengths of PVC pipes, with one pipe able to slide inside the other like a syringe plunger, where we would fill the larger pipe with concrete, then use the smaller pipe to push the concrete through larger pipe through the hose.
Making a concrete hopper above ground and then running a hose from that to the forms, kind of like a big beer bong, where we pour the concrete in the hopper and it would just flow into the forms (using some really low-viscous concrete).
Making a trough setup where we could load the mud in from above ground and then push it along in the trough to the forms.
Carrying buckets of mud under the house.
Drilling through the floor where the footings are. I like this, but the wood flooring is car-deck flooring with the tongue-and-groove joints on the sides, so that they are actually structural members. The foreman is afraid if we drill through the floor, the flooring would become structurally weakened. I would think a 2" hole in the 4-5" wide flooring piece wouldn't be that bad, but its his call.

Any other innovative suggestions as to how to transport the concrete? This is a Habitat for Humanity project so there's not a lot of money we can throw at it.

The prefabbed form boxes


Underneath the house showing the footings:



Our access to under the house:


Kolea
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Nighthawke
Nighthawke

February 12th, 2012, 9:17 pm #2

It'll be slow, almost painful moving mud that way, but on you guy's budget, a pump truck is out of the question unless you can find an operation that can donate a couple three hours time on a pump truck that is between jobs.

Also moving mud in troughs will cause the mix to separate a little, so it'll need to be remixed when it reaches the form by using trowels or shovels.

DO NOT add extra water to the mix, for it will weaken it and the goal here is strength.

Get a gravel base laid down, then a 10mil plastic liner, then top off with concrete. That will be your ideal configuration for that kind of project. This will prevent moisture and mold from building up. OPEN the crawl space ventilation, and keep it so! Make sure that the homeowner understands that once the crawlspace is sealed with concrete, it will have the potential of making mold and radon gas down there, so ventilation is a must!

http://www.emecole.com/pages/Cosmetic-A ... azard.html
http://www.dirt-crawl-spaces.com/crawls ... ation.html
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akpirate
akpirate

February 13th, 2012, 12:39 am #3

Hey,

I volunteer with Habitat for Humanity, and the current house that we're working on needs to be jacked up a little bit since its sagging in the middle. The foreman wants to pour back some concrete around the current concrete footings that are under there, since there has been mild-to-considerate erosion under the footings and they're no longer fully sitting on the ground.

We've got these form boxes that we're going to put around the footings and nail together. The problem is getting the concrete into the forms. There are three rows of four footings and almost all of them need poured back.

Things we're considering but not fully bought into yet:
We've tossed around making a mini concrete pump out of some hose and lengths of PVC pipes, with one pipe able to slide inside the other like a syringe plunger, where we would fill the larger pipe with concrete, then use the smaller pipe to push the concrete through larger pipe through the hose.
Making a concrete hopper above ground and then running a hose from that to the forms, kind of like a big beer bong, where we pour the concrete in the hopper and it would just flow into the forms (using some really low-viscous concrete).
Making a trough setup where we could load the mud in from above ground and then push it along in the trough to the forms.
Carrying buckets of mud under the house.
Drilling through the floor where the footings are. I like this, but the wood flooring is car-deck flooring with the tongue-and-groove joints on the sides, so that they are actually structural members. The foreman is afraid if we drill through the floor, the flooring would become structurally weakened. I would think a 2" hole in the 4-5" wide flooring piece wouldn't be that bad, but its his call.

Any other innovative suggestions as to how to transport the concrete? This is a Habitat for Humanity project so there's not a lot of money we can throw at it.

The prefabbed form boxes


Underneath the house showing the footings:



Our access to under the house:


Kolea
A couple of rubbermaid totes with some optional rope. Use too big of a tote and it becomes too heavy for one person to effectively drag under the house. Lay down some strips of plywood or 2x material makes for a easy surface to skid the totes anywhere you need.

None of that other stuff you mentioned is worth the time to set up for such a small job. One person mixing and one person under the house waiting by the opening with totes to be filled. Of course the more people hte merrier, but otherwise two people should have a concrete pour like that done in time for lunch.

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MephitMark
MephitMark

February 14th, 2012, 1:39 am #4

Hey,

I volunteer with Habitat for Humanity, and the current house that we're working on needs to be jacked up a little bit since its sagging in the middle. The foreman wants to pour back some concrete around the current concrete footings that are under there, since there has been mild-to-considerate erosion under the footings and they're no longer fully sitting on the ground.

We've got these form boxes that we're going to put around the footings and nail together. The problem is getting the concrete into the forms. There are three rows of four footings and almost all of them need poured back.

Things we're considering but not fully bought into yet:
We've tossed around making a mini concrete pump out of some hose and lengths of PVC pipes, with one pipe able to slide inside the other like a syringe plunger, where we would fill the larger pipe with concrete, then use the smaller pipe to push the concrete through larger pipe through the hose.
Making a concrete hopper above ground and then running a hose from that to the forms, kind of like a big beer bong, where we pour the concrete in the hopper and it would just flow into the forms (using some really low-viscous concrete).
Making a trough setup where we could load the mud in from above ground and then push it along in the trough to the forms.
Carrying buckets of mud under the house.
Drilling through the floor where the footings are. I like this, but the wood flooring is car-deck flooring with the tongue-and-groove joints on the sides, so that they are actually structural members. The foreman is afraid if we drill through the floor, the flooring would become structurally weakened. I would think a 2" hole in the 4-5" wide flooring piece wouldn't be that bad, but its his call.

Any other innovative suggestions as to how to transport the concrete? This is a Habitat for Humanity project so there's not a lot of money we can throw at it.

The prefabbed form boxes


Underneath the house showing the footings:



Our access to under the house:


Kolea
And I'm not talking about the multi jointed arm rigs. I know there are rigs that pump the concrete through special hoses.

Question being can you rent a unit, or do you have to hire one?
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akpirate
akpirate

February 14th, 2012, 5:43 am #5

With only 12 concrete pads to pour around already existing footers we're only talking about maybe 50cuft of concrete at the most. Those concrete pump trailer require almost that much just to fill the hopper and hose( depending on the length of hose)

The hoses themselves filled with concrete are a couple hundred pounds per section and are not very flexible.

Dont get me wrong I'm all for mechanized labor, but this is one of those times when human sweat does it better, faster and cheaper.
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Kolea
Kolea

February 14th, 2012, 7:05 am #6

And I'm not talking about the multi jointed arm rigs. I know there are rigs that pump the concrete through special hoses.

Question being can you rent a unit, or do you have to hire one?
With a concrete pump, is its pretty big, and it costs $$$, and since its a Habitat project, we don't exactly have $$$ to spend.

I come from a Heavy Civil construction management background, so concrete pump is the first thing I thought of, but thats because we used to have a nice budget

K
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Bruce Bergman
Bruce Bergman

February 14th, 2012, 7:00 pm #7

It'll be slow, almost painful moving mud that way, but on you guy's budget, a pump truck is out of the question unless you can find an operation that can donate a couple three hours time on a pump truck that is between jobs.

Also moving mud in troughs will cause the mix to separate a little, so it'll need to be remixed when it reaches the form by using trowels or shovels.

DO NOT add extra water to the mix, for it will weaken it and the goal here is strength.

Get a gravel base laid down, then a 10mil plastic liner, then top off with concrete. That will be your ideal configuration for that kind of project. This will prevent moisture and mold from building up. OPEN the crawl space ventilation, and keep it so! Make sure that the homeowner understands that once the crawlspace is sealed with concrete, it will have the potential of making mold and radon gas down there, so ventilation is a must!

http://www.emecole.com/pages/Cosmetic-A ... azard.html
http://www.dirt-crawl-spaces.com/crawls ... ation.html
They aren't going to try pouring a floor in the crawl space, they are only digging out and pouring new footers for the pier bases. All you need to do to the dirt under the house is clean out all the crap that's down there.... Bring in some Decomposed Granite sand to make it easier on your knees if you're going to be down there a lot.

For getting the concrete to your form boxes, I'd make a little flat-cart that breaks apart and can be reassembled inside the crawl space - a simple platform out of welded angle and telescoping square tubing, and a sheet of plywood dropped in the channels, with a Low-Boy bed an inch off the ground, and 4 small (4") pneumatic tires that remove with pins - swivel caster wheels may be more trouble than it's worth, go with straight lines and horse it around the turns.

I can see a few ways to whip up a flat cart with a small MIG Welder and a few clevis pins - if you need a sketch, let me know. Would also be good for getting the rebar and forms in, and all the trash out in the same buckets.

Then get 5-gallon plastic buckets - or 3-gallon Shorties if 5's won't fit through the crawl hole. Don't worry too much about separation "in transit", it will get remixed when you place the mud.

Get some new rebar in there to make sure your new pad stays in one piece. Doesn't have to be fancy, just a hoop or two to keep it from splitting. Put it up on dobies so it stays where it will do something.

And GET A CONCRETE VIBRATOR! (The #34923 drill style from Harbor Freight would be plenty.) That makes sure the mud is totally mixed and you have the air out, and it's tight to the forms and the old bases.

A concrete pump would be best, but they cost a few bucks - and you have to get a truckload of Pump Mix concrete with smaller aggregate to fit through the hose.

The small hose isn't too bad to fight with, as long as you start at the FAR end with the hose empty, then you have the crew outside do the hardest work pulling the hose back out as you get closer to the crawl hole - all the people under the house have to do is keep it from getting hung up.

The pump crew can break the hose and remove sections as you get closer to the crawl hole.
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Bruce Bergman
Bruce Bergman

February 14th, 2012, 7:16 pm #8

Hey,

I volunteer with Habitat for Humanity, and the current house that we're working on needs to be jacked up a little bit since its sagging in the middle. The foreman wants to pour back some concrete around the current concrete footings that are under there, since there has been mild-to-considerate erosion under the footings and they're no longer fully sitting on the ground.

We've got these form boxes that we're going to put around the footings and nail together. The problem is getting the concrete into the forms. There are three rows of four footings and almost all of them need poured back.

Things we're considering but not fully bought into yet:
We've tossed around making a mini concrete pump out of some hose and lengths of PVC pipes, with one pipe able to slide inside the other like a syringe plunger, where we would fill the larger pipe with concrete, then use the smaller pipe to push the concrete through larger pipe through the hose.
Making a concrete hopper above ground and then running a hose from that to the forms, kind of like a big beer bong, where we pour the concrete in the hopper and it would just flow into the forms (using some really low-viscous concrete).
Making a trough setup where we could load the mud in from above ground and then push it along in the trough to the forms.
Carrying buckets of mud under the house.
Drilling through the floor where the footings are. I like this, but the wood flooring is car-deck flooring with the tongue-and-groove joints on the sides, so that they are actually structural members. The foreman is afraid if we drill through the floor, the flooring would become structurally weakened. I would think a 2" hole in the 4-5" wide flooring piece wouldn't be that bad, but its his call.

Any other innovative suggestions as to how to transport the concrete? This is a Habitat for Humanity project so there's not a lot of money we can throw at it.

The prefabbed form boxes


Underneath the house showing the footings:



Our access to under the house:


Kolea
Especially the pier that's sinking at an angle, that sucker needs to be totally gone and poured from scratch. Get out the bottle jacks, Crib it up with railroad ties a few feet to each side, then get a small demo hammer and make it disappear - then dig down another foot or so and start fresh.

You might be able to take the load off and level the existing pier base when you pour underneath, but don't leave it cockeyed and try to fix it.

Even then, there's no visible anchors bolting the pier timber to the joist timbers or the pier base - that stuff needs to be bolted together in case of "Negative Loading" - earthquake, hurricane, tornado, etc. You don't want the house to go up and the pier timber to fall over, that gets real messy when the house comes down again. Simpson steel pier bases with bolted yokes, and some bolted tee plates where it ties into the joist timbers.

Some of the other piers just need to be dug out from underneath and pour another foot down - but they still should be cribbed first. You don't want the house falling on you as you work.

Read my other post about building a little cart to move the Rubbermaid Totes or 5-gallon buckets with the concrete. Dragging does work, but why kill yourselves? Make it roll. You might even put eyes on each end of the cart and rig up some haul ropes to get it in and out easier.
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smorizio
smorizio

February 15th, 2012, 2:36 pm #9

i would get a furnuter dolly from local rental store one of the wood ones.make a small box to fix a tote on top of it.on the dolly put a i hook that you can hook a cable winch from a truck to.use the winch to pull the slead for you one way. use a close line set up to pull the tub the other way.
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