mountain/mole hill. It's a stick framed garage. You wasted a lot of concrete. I wouldn't worry about it.
What you DO need to do is make sure the slab gets done right. Are you playing contractor or do you have one? Either way, educate yourself and make sure the slab is done right.
Drainage
Reinforcing steel
Cure time control
Vaper barrier
Car lift specs
Back fill
etc.,etc., so forth and so on.
Much ado about nothing.
This is Atlanta GA. The frost line is 5". It's a wood frame building. You literally could have built it without a footing at all.
The 12" footing was designed to hold the weight of the concrete (stem wall), and it sits on undisturbed red GA clay (one of the best building materials available). You haven't added weight, and won't have a (n additional) settling problem.
If you tell them to jackhammer it out and redo it, you can kiss your 50% deposit goodbye. You'll be looking for another concrete guy (and have to pay him for both the demo AND the job).
Have them drill long threaded rod through the footing with epoxy for your anchor bolts. It will also act as vertical reinforcement.
Just make sure you get your waterproofing and drainage right. Wet soil is heavy against that stem wall.
Great to see your progress! Keep up the good work! (And call me for your framing party!) 😊
In reply to SV reX :
From a 8" wall to a 24x30 inch block is a huge amount of weight added ,something like 40,000 pounds .I wouldn't be worried at all about vertical reinforcement as much as horizontal. Sure it's a light building but here with frost and water I'd be worried about it cracking and letting water thru leading to more cracking.
The thing that worries me the most though, no concrete guy would think to fill up the trench without more rebar. So either his help really sucks, or they as a unit do.
The "extra compaction so the slab won't settle" is also concerning. It doesn't take much movement to crack a slab, and GigantoFooting is gonna settle. Id be more inclined to throw a lot more steel in but it sort of sounds like it's just gonna have fiber.
Mostly though I'm alarmed to see this happening in an absolutely butt simple job, I wouldn't want them doing my concrete.
maschinenbau said:Isn't this basically a normal basement foundation footing but with a mega huge block underneath it all?
It is, but that not what you have. You have a huge non reinforced block of weight that technically really isn't a concrete foundation. Concrete by itself isn't really strong, but reinforced concrete is exceptionally strong.
Basically they seem to be selling you on you getting something stronger, but in reality you are getting something weaker
Also I have seen someone do something sort of similar, he is an electrical engineer and thought huge amounts of concrete means strength.
He had it 3 feet below ground and 1 foot above. It's cracked apart a lot
It's not an increase from 8" wall to 24" x 30". The original planned footing was 12" x 24", so the difference is 18" x 24". It's 66 cubic feet of concrete per wall. Concrete weighs about 150 lbs per cubic foot. That's 9900 lbs evenly distributed over 44 square feet- that's 225 lbs per square foot. About the same as a man standing on it.
I repeat... much ado about nothing.
In reply to SV reX :
9900 a wall equals roughly 40k for the building, you are saying the same thing as I am.
I don't know what the grounds like there vs here, here that would be a massive problem.
And I cannot stress this enough, no one that does concrete would have done that. " Whoops, gonna have to order another full truck of concrete for this foundation". It's very strange.
Antihero said:Also I have seen someone do something sort of similar, he is an electrical engineer and thought huge amounts of concrete means strength.
He had it 3 feet below ground and 1 foot above. It's cracked apart a lot
This failure had nothing to do with too much concrete. It had to do with improper reinforcement, poor compaction, inadequate substrate materials, bad materials, poor workmanship, or all of the above.
I routinely pour concrete 4 feet thick with no issues, and have poured it 8 feet thick.
The foundation was over designed for this structure, and the soil bearing capacity exceeds 3000 lbs per square foot. There are no point loads in the building. That footing should not have any problem supporting the additional weight of the excess concrete.
If the local building authorities have no problem with it, then there is no problem.
In reply to Antihero :
I agree. It's very strange.
I agree that we are talking about similar overall weight, but it's evenly distributed over 176 square feet of bearing area (225 lbs per square foot), with a soil bearing capacity of 3000 per square foot.
SV reX said:Antihero said:Also I have seen someone do something sort of similar, he is an electrical engineer and thought huge amounts of concrete means strength.
He had it 3 feet below ground and 1 foot above. It's cracked apart a lot
This failure had nothing to do with too much concrete. It had to do with improper reinforcement, poor compaction, inadequate substrate materials, bad materials, poor workmanship, or all of the above.
I routinely pour concrete 4 feet thick with no issues, and have poured it 8 feet thick.
The foundation was over designed for this structure, and the soil bearing capacity exceeds 3000 lbs per square foot. There are no point loads in the building. That footing should not have any problem supporting the additional weight of the excess concrete.
If the local building authorities have no problem with it, then there is no problem.
Yes but as a comparison to this project it has the same issues. Compaction is the one thing that I cant quantify but the others, yes .
Concrete can be poured thick, I'm not sure where you are going with that. I've poured bank vaults, I've poured dams and they were also very thick but they had adequate steel in them. I've even done a few domes and those have massive footings with ridiculous amounts of steel thru them. It's a totally different animal because of the constant outward pressure, but yes it was 8'x 4' with #5 steel 6" on center with even bigger steel inbetween.
If the ground can handle the additional weight, and since I'm not there I can't say for certain, that part is ok. But still.......non reinforced concrete foundation. That he's probably paying good money for. Not ideal
But that moves us onto the next issue of the slab. The contractor he's using already admits there is gonna be a settling problem. I'm not sure how much we can count on his expertise but he has poured at least one more than I have in the area and he's concerned. This is......well ...... concerning.
Seriously, hes signing onto an experiment funded by his money and one that he didn't know about going in. At the very least I'd make an engineer sign off on it and spec a different level for the slab to prevent sinking just to protect an investment.
God knows what they will do with the slab though after seeing this. This is like chewing thru the glass bottle to get to the beer instead of taking the cap off. I guess it works .....but why?
I am not defending their mistake and neither is the contractor. He is fully aware (and mad) that it was over-poured, and he is eating that cost already. I think no one was there to supervise during the pour and the helpers just keep pouring. Obviously if I had known this would happen, I wouldn't have hired them. But this is where I'm at, and I'm happy to move forward with the easier solution of keeping this huge chunk and drilling into it, as long as it's not a real problem.
In reply to Antihero :
You didn't say the failed job had inadequate steel. You only said it was thick. I responded based on what you said.
I see nothing posted about the contractor admitting there will be a settling problem.
I agree there is nothing wrong with asking for an engineer to sign off on it. It's a much better approach than asking us internet armchair engineers for solutions! (It would make all of us obsolete!) 😂😂
SV reX said:In reply to Antihero :
I agree. It's very strange.
I agree that we are talking about similar overall weight, but it's evenly distributed over 176 square feet of bearing area (225 lbs per square foot), with a soil bearing capacity of 3000 per square foot.
Is that bearing with no movement whatsoever? Or is it that it will sink slightly but not sink out of sight? Does that include them compacting after digging the trenches? How does water effect it?
Concrete can crack with very little movement since it's so brittle. And a huge mass moving even a little is still a lot of force. The slab is now connected to the GigantoFooting totally rather than floating. It's definitely not ideal.
In reply to Antihero :
It was undisturbed clay. That's a very typical condition in this region.
They didn't overdig or build on fill.
And floating slabs are very rarely done in the South. That's a Northern detail.
SV reX said:In reply to Antihero :
You didn't say the failed job had inadequate steel. You only said it was thick. I responded based on what you said.
I see nothing posted about the contractor admitting there will be a settling problem.
I agree there is nothing wrong with asking for an engineer to sign off on it. It's a much better approach than asking us internet armchair engineers for solutions! (It would make all of us obsolete!) 😂😂
Looking back, you are right I didn't mention the steel. He put 2 bars of #4 a foot off the ground
He is utterly terrified of rust intrusion on rebar because he saw a dam start to collapse from the " rust blowing the concrete off the dam" in fact he would probably weep seeing that these guys staked in rebar to hold the rebar up.
We had several discussions on fiber vs rebar too. In the end the numbers look good on fiber but it only strengthens concrete, it doesn't reinforce it. I did pour him a sidewalk with only fiber so he could see the results with the caveat that it's his money and he will be paying me to rip it out and report it when it cracks and his wife doesn't like it.
Guess who is replacing it this spring? Lol
It was just something the OP said about them wanting to go way overkill on compaction. So they are worried too but probably trying to save themselves thousands of dollars and eek by
A foot off the bottom of the footing made the steel basically useless. Should have been about 3".
Footings are in tension at the bottom, and compression at the top. Concrete sucks in tension- it's excellent in compression. By moving the steel up a foot he expected the concrete to survive the being in tension at the bottom of the footing. That's bad.
He said they would over compact under the slab (not the footing). It was a weird comment, and unnecessary.
maschinenbau said:I am not defending their mistake and neither is the contractor. He is fully aware (and mad) that it was over-poured, and he is eating that cost already. I think no one was there to supervise during the pour and the helpers just keep pouring. Obviously if I had known this would happen, I wouldn't have hired them. But this is where I'm at, and I'm happy to move forward with the easier solution of keeping this huge chunk and drilling into it, as long as it's not a real problem.
It's good that he's not defending the mistake and I personally didn't think you were.
I don't know, I'd have an engineer sign off on it and spec you a slab to help prevent sinkage. At the very least you want to have some coverage for you in the future there.
What are the steel specs on the slab originally?
All I can say is this is baffling and weird and I wouldn't want my money transferred to a "professional" with this being the end result. I don't know if I'm wording it well enough but essentially you really shouldn't pay for expertise and get.....this
In reply to Antihero :
You have a point about the rebar stuck in the soil. I missed that.
Getting an engineer to sign off is a good idea.
SV reX said:A foot off the bottom of the footing made the steel basically useless. Should have been about 3".
Footings are in tension at the bottom, and compression at the top. Concrete sucks in tension- it's excellent in compression. By moving the steel up a foot he expected the concrete to survive the being in tension at the bottom of the footing. That's bad.
He said they would over compact under the slab (not the footing). It was a weird comment, and unnecessary.
Exactly, and looking at the pics above it kinda looks like they placed theirs at about 8"? Scale isn't clear.
They are saying it because they are worried about the slab being dragged down by the GigantoFooting. Essentially they are hoping their slab will hold up everything from moving. They want to massively compact the subbase under the slab because instead of it having to hold 42,000 pounds, it now has to hold it has to hold 150,000 pounds without it moving.
I guarantee that's what they are worried about from what they say
In reply to Antihero :
That's too much speculation for me. I'm only responding to the question "Is a 30" thick footing a problem?". I'm not gonna guess why the contractor makes a weird unrelated comment.
Its just as likely he is trying to look like he is willing to go the extra mile to make up for the mistake.
SV reX said:In reply to Antihero :
That's too much speculation for me. I'm only responding to the question "Is a 30" thick footing a problem?". I'm not gonna guess why the contractor makes a weird unrelated comment.
Its just as likely he is trying to look like he is willing to go the extra mile to make up for the mistake.
It's not unrelated though really
Essentially this is closer to a mono pour without steel connecting the footing/wall to the slab, with more steps than a monopour....and not really that but I guess it's closest?
The thing is, fixing stuff like this was literally how my company took off. There were a few very terrible contractors in the area and for the first few years their work was the best advertisement I could get. I would either lose a bid to them because they were a bit cheaper or I would remove and replace their work after a few months or a year. It's sort of Forensic Concrete.
I guarantee that is his issue and he mentioned because he's very worried about it. It's the same ground that's under the footings, so he shouldnt be worried about it being bad ground that needs to be mitigated . He's worried because the ground may not be able to hold all the weight and he wants it to be better.
And from the pics and my experience.....he has reason to be.
To be clear, the contractor never mentioned settling issues. I brought that question up while talking about the over-pour and he didn't seem concerned, but would be willing to do whatever I require to the slab to make me okay with it. We have not yet discussed a tear-out. I am inclined to simply call the county inspector, explain what happened and what we plan to do, and see what they say. My gut (as a ME, not Civil) says it's probably going to be fine.
maschinenbau said:To be clear, the contractor never mentioned settling issues. I brought that question up while talking about the over-pour and he didn't seem concerned, but would be willing to do whatever I require to the slab to make me okay with it. We have not yet discussed a tear-out. I am inclined to simply call the county inspector, explain what happened and what we plan to do, and see what they say. My gut (as a ME, not Civil) says it's probably going to be fine.
It's not a bad idea, they will probably ask for an engineer to sign off on it if they are anything like they are here. No matter what our skill sets are on here, we are still just looking at pics on a screen and are not there.
I could see them specing a bond breaker between the slab and GigantoFooting with some tricky water proofing on the outside. It'll mean your slab has to get deeper on the edges so you can use j bolts for the framing. There will be other issues too I'm sure.
But really, essentially this means he has idiots working for him, he was ok with sending them to your job and risking your money for it and will more than likely continue to do so
You seem like you like him, at least well enough, but be very very wary here. This is not a great path in front of you
In reply to maschinenbau :
I know I am the one who recommended you talk to the building inspector. I've changed my mind.
He should have failed the inspection. The rebar in contact with the soil is not an acceptable technique. So, I question the inspector's competence.
A footing design from a structural engineer shouldn't cost much. If your concrete contractor actually wants you to be good with the overpour, getting an engineer to sign off on it should shouldn't be a problem.
Best luck!
SV reX said:In reply to maschinenbau :
I know I am the one who recommended you talk to the building inspector. I've changed my mind.
He should have failed the inspection. The rebar in contact with the soil is not an acceptable technique. So, I question the inspector's competence.
A footing design from a structural engineer shouldn't cost much. If your concrete contractor actually wants you to be good with the overpour, getting an engineer to sign off on it should shouldn't be a problem.
Best luck!
It's a valid point.
I was trying to not say " your project sucks, your contractor sucks, and your inspector sucks" but yeah........
And I'm also trying to not say that the longer you wait to remove the worse it is because an hour after it was poured it's a sucky job but doable. A day after it's terrible but still ok.
A month later it's a huge and terrible job that requires a lot of equipment.
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