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greghamilton 07-29-2013 07:02 PM

How To Repair Large Hole In Foundation
I had to open up my foundation to access my pipes for a plumbing repair. I have looked on You Tube, etc. and have not found any information on how to repair a large hole in a concrete foundation. If you look at the pictures in the attached link, you will see what I am talking about. Especially look at #727 & #730. It is basically a 5' x 2.5' hole all the way through 8" of concrete. The strange thing is there was not a shred of steel rebar that I encountered while jack hammering the hole, so I would have to guess there's none in the rest of the house either.

People have told me to rent a hammer drill and drill holes into the foundation laterally, then shove pieces of rebar into the holes and create kind of a weave. Of course, first I would have to fill in with dirt and sand and tamp it down I guess. But, when I am finished, it is important that it is level and that it can support our bath tub. I have figured that with the tub I want to get, with it full of water, and with a person in the tub, it will weigh close to 900 lbs. and unfortunately, right now, two of the feet of the tub don't have any concrete to stand on, so it has to be a really, good patch job. Also, what about the black plastic vapor barrier? How important is that really since it would not be contiguous with the whole slab anyway?

stadry 07-30-2013 06:52 PM

looks like you open'd the floor, not the foundation, right ? what suggested you'd find steel or even wire mesh ?

IF it were ours, i'd fill w/road base mtl - we call it ' graded aggregate base ' here or ' run of crush / crusher run,,, #57 stone mix'd w/stone dust,,, wet & compact,,, place a vapor barrier on its surface prior to placing the conc,,, finish the conc level & it'll hold 6 bathtubs :laughing: from the looks of the jagged edges of the hole, you won't need rebar in the existing/old conc,,, CLEAN & DAMPEN the sidewalls prior to placing the conc,, the wtr you apply will prevent the dry existing conc from sucking out the new conc's moisture & leaving weaker conc in its place

good luck !

greghamilton 07-30-2013 08:23 PM

Wow, that sure sounds alot easier than what I was thinking about doing. I guess I always thought there was rebar in the concrete and from talking to other people down here. I'm not sure what the distinction is between flooring or foundation as you call it. I usually think of flooring as tile, wood, carpet, and I think of foundation as being the whole area of concrete that the house sits on, or the slab.

Without any rebar to attach the patch to the main foundation, what keeps it from sinking down and compacting the sand and dirt down further? Should I tamp down the dirt in that 4 foot hole in the dirt that is below the slab? Does it matter if I use sand or dirt, should I wet it and pack it and do layers? Also, what is the deal with the electric tape looking stuff around the copper lines as it comes up through the slab?

All that stuff you called what you would use to fill the hole, is that something I can mix myself in a wheelbarrow?

stadry 07-30-2013 08:50 PM

in tx, its not uncommon to find cables tensioning the slabs due to expansive soils,,, not knowing if your home's 1 or 2-story, its difficult to guess,,, cutting a cable is serious stuff altho not fatal to home's integrity.

generally a foundation is 1st then bsmnt walls are placed on top of the fnd & the house is blt on top of them,,, THEN the conc floor's placed in the bsmt,,, flooring can be decorative conc or any other applied traffic tolerant surface - carpet, tile, engineer'd wood, etc .

its the dirt that keeps conc from sinking when its plastic ( wet ),,, after the conc cures, its flexural strength keeps it from sinking,,, it doesn't weigh enough to impact the base ( sand/dirt ),,, sand isn't a good choice as you can't compact it properly,,, yes, place in layers ( lifts ) & compact w/some moisture

' electric tape looking stuff around the copper lines as it comes up through the slab ' - no idea,,, anyone ?

the gabc is usually bought as is,,, here in atl anyways,,, since you're so new & still ignorant ( there's a cure for ignorance whilst stupid is often fatal ), do you know anyone experienced who could help ? learning's fun when you don't f up :whistling2:,

joecaption 07-31-2013 05:46 AM

If at all possible I would replace all those old copper lines with Pex while it's still open.
At some point it's going to leak when run through a slab.

greghamilton 07-31-2013 11:29 AM

itsreallyconc, We have a one-story house. No basements in Texas, it's too flat and the ground moves too much I guess. What are your suggestions for the base? I looked up plastic as an adjective and it mentions clay. Should I just use dirt and wet it, then compact it? Do I need to use a tamper or just carefully stomp on it and use my hands to push it down? What kind of dirt should I use? The material that was down in there originally, and I was planning on re-using it after sifting out all of the chunks of concrete, was kind of an orangish color. By wetting this dirt, I guess it will drive my A/C crazy since it also works to keep our humidity down. I guess I would lay down a layer of thick black plastic on top of the base just before I lay the concrete, right? I'm pretty sure the reason for the black plastic tape looking stuff around the copper pipes as it goes through the slab is for when the slab moves relative to the ground itself, but then again, the slab has hold of those pipes so good it would just move the pipes too. The gabc as you called it hopefully comes in a bag because this bathroom is kind of in the center of our house, so it's hard to envision a concrete truck extending its chute into our bathroom, plus I'm trying to stay away from high cost adventures like that too. No help, I'm sure I could cry uncle and take out a home equity loan, but I'm too stubborn..... and ignorant on some things too, ha ha.

joecaption, I appreciate that advice and it is probably good advice, but I think I am going to gamble that I can outlive that problem, or I guess I would have to say the reverse of that. I'm almost 50 and I'm really hoping those lines will hold another 20-30 years since they have already held about 30 years already. When I saw them, I did notice they are very corroded, but even if I replaced them, there are about 10 times that many more copper pipes going all over the rest of our house, so I think I will just have to take a chance.

Thanks to both of you for all of your suggestions.

stadry 07-31-2013 04:16 PM

i suggested granulated rock from a landscape supply or quarry crushing plant,,, put back what was there ( IF you still have it ) as you plann'd,,, for compaction, just walk on it w/old shoes :laughing: your a/c won't mind a bit :no: when you finally mix up conc, do it right beside the hole,,, @ 4" thick, ea 80# bag yields 2sf :yes:

' 10 times that many more copper pipes ' means its prudent you heed mr joe's advice while the floor's open :thumbsup: then gain, as you said, you're still young so maybe you'll have time ti revisit it again,,, when / if you do, remember joe :whistling2:

greghamilton 07-31-2013 10:28 PM

I will definitely take yours and Joe's advice under consideration on the replacement on the copper piping.

As far as filling in the hole, if I need more material to fill the hole in other than the dirt I have piled up in my bathroom that came out of there, what would you suggest using? I might not need anything since I did not get rid of anything that I dug out of there, but then again, I plan on packing it pretty good, because I really don't want the patch to sink down in the middle since two of the four feet of the bath tub will be sitting on the patch and I want it to be level.

This granulated or crushed rock you are talking about, I would imagine you are saying to mix this in the concrete to give it more strength. Is that correct? On the 80lb bags, I usually use the regular yellow bag stuff for various projects. Is that what you would suggest? Thanks.

stadry 08-01-2013 02:40 AM

i apologize as evidently my posts have been not easily understood.

IF you saved everything that came out, make sure it ALL goes back in,,, that will assure you of proper soil compaction,,, the mentioned ' gab ' ( aka ' gravel ' ) was for addl fill IF you needed it - NOT to add to bagg'd conc mix :no:

greghamilton 08-01-2013 03:13 AM

Oh, okay. I'm sure it's more me than you as far as not understanding. I am thinking about using the yellow bag quickrete or the white bag quickrete The white bag stuff gets up to 5000 psi on its compressive strength whereas the yellow bag stuff only gets up to 4000 psi. The white bag stuff says specifically is for stuff over 2" thick. Do you think either of these would work?

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