Any concrete experts here?

[brushsjigs]

I would say its just going to cover it up temporarily and look ugly. I know the crack makes you sick but there is not much you can do from here. Ground will always be moving.

[Phoenix Dreaming]

Lots of ways to pour concrete and things can be done to keep from cracking. If all you got was straight pour concrete on unpacked foundation it is not surprising it cracked.
Had you required a 10 year warranty on no cracks they would have handled it different and you would have paid considerable more for work.

I highly doubt a house pad, garage pad, etc...will ever be provided with a 10 year no crack guarantee. We have done a few guarantees for commercial warehouses like that but the admixture, finishing, etc...is expensive along with the guarantee.

By the way, you dont pour concrete, you place it. If you are pouring it your slump is too high.

[weim hunter]

Can you stick a nickel in it?

[lakefolk]

Can you stick a nickel in it?

i don't see a nickel helpin much.....

[weim hunter]

Yeah, I've never seen that either. State requires 10 year structural warranty on new construction here. However, I've never seen anyone consider messing with anything under 1/8". They consider anything under that "normal". An old concrete finisher told me he always carried a quarter around with him to check cracks.

I highly doubt a house pad, garage pad, etc...will ever be provided with a 10 year no crack guarantee. We have done a few guarantees for commercial warehouses like that but the admixture, finishing, etc...is expensive along with the guarantee.

By the way, you dont pour concrete, you place it. If you are pouring it your slump is too high.

[weim hunter]

Lol. I meant quarter, but that won't help him fix it much either. Old concrete finisher told me years ago that's what he always uses to judge cracks.

i don't see a nickel helpin much.....

[DoctorJJ]

I wouldn’t ever pour anything that was going to have a structure on it that didn’t have a footing of some kind. Call it a garage, shed, whatever. I bet if you asked the manufacturer of the pre-fab, they would recommend a footing.

And flat work should start at about $3/sq foot. Higher for thicker concrete, stronger concrete, etc. that includes steel. I would want to pay $3000 max for what you got. Everywhere is different though.

[grout-scout]

I disagree with these statements. If proper sub grade, PI should be proper for the slab. If the contractor installed control joints/saw cuts properly, the concrete would have cracked where they were placed. Control joints are an integral piece of slab Construction.

I’m not sure what you think you’re disagreeing with, saw cuts or not, it’s still a crack.

[Tigercat]

Joints should’ve been cut. The price isn’t bad for what was done. But he should’ve priced it to do it right and clarified a cheaper price based off of what he wasn’t going to do. My biggest concern would be subgrade prep. The fact that you said 12 tons of “dirty” crusher run leads me to believe he didn’t spend much time on subgrade. For one, you wouldn’t want to use any aggregate material that is contaminated with other materials under anything structural. Additionally, 12 tons would barely cover the area. Just for looks or just to level up a poorly prepped subgrade. Using 4” of material, bare minimum IMO, would be close to 75 tons. If I spent time to get the subgrade right, I would cut corners and jeopardize my work afterwards. You can live with the cracks, but it will be a problem if the cracks are showing already because of poor, organic materials under the slab. Those will continue to move, breakdown and decay, causing settlement, voids and other problems in the years to come. Hopefully this isn’t the case though.

[haftafish22]

I’m not sure what you think you’re disagreeing with, saw cuts or not, it’s still a crack.

I disagree with the statement that it’s acceptable for the sub grade to move. Come work on what I do....35 stories you better have a solid sub grade and pier system.

[Tigercat]

I disagree with the statement that it’s acceptable for the sub grade to move. Come work on what I do....35 stories you better have a solid sub grade and pier system.

Agree. Concrete doesn’t always crack and subgrade is not supposed to move.

[grout-scout]

I disagree with the statement that it’s acceptable for the sub grade to move. Come work on what I do....35 stories you better have a solid sub grade and pier system.

So faults in the earth won’t move, soil doesn’t expand & contract? Now you want to compare a 35 story building prep to a garage floor that cost $6k. You guys are killing me!


Every house we have built and had an engineered slab for had tiny fine print at the bottom talking about expansive soils and how it’s the home owners job to water the perimeter of the slab weekly with 1” of water (Or some hogwash that nobody will ever do) and if you didn’t follow their proper protocol, it was not their responsibility if the slab were to fail.

[Riccochet]

slab's are not pillar bedded like a high rise building. Completely different construction.

And relief cuts are made so you DON'T see the crack. It still cracks and expands.

Even footed slabs still crack. There's no stopping the earth from moving. That's totally dependent on location. Some places move less than others.

[barbarian]

Some of y’all should never come to Houston and buy a house. 100% of house slabs and driveways will have cracks similar to OP’s picture. Most within first 5 days.

[ECobb91]

Two thoughts that come to mind

1. The 5” depth is pretty thin for heavy loads. Typically, sidewalks are 4” and driveways are 6”. If it cracked already it could be due to the dead load or the concrete wasn’t up to spec. Any reputable concrete company would have an ACI certified concrete tester and finisher on site. Even for residential properties it’s always good to have a slump test and air test done. Along with the thin concrete, most guys like to add more water to make it easier to work, but that means weaker concrete. The tests make sure the concrete is within acceptable limits.

2. 12 tons of sub base is fine and dandy, but sub base is actually estimated in CY not tons. He might have screwed you on that alone. The tons mean nothing. Do you know how deep the sub base goes? That could be a reason why. And the most glaring reason is they didn’t compact it enough.

the reasons why concrete (especially new) cracks: 1. Poor concrete material, 2 not thick enough, 3. Subbase isn’t thick enough 4. Subbase wasn’t compacted enough.

[grandbassslayer]

So contractor called me back today. And is going to come take a look at. He mentioned grinding the crack and feeling with some type of concrete calk. Should I allow him to do this. Will it fix the problem and prevent farther cracking ? Or just cover up the problem ?

First its not even a problem based on the pictures, so don't get too worried about it.

[Tigercat]

Two thoughts that come to mind

1. The 5” depth is pretty thin for heavy loads. Typically, sidewalks are 4” and driveways are 6”. If it cracked already it could be due to the dead load or the concrete wasn’t up to spec. Any reputable concrete company would have an ACI certified concrete tester and finisher on site. Even for residential properties it’s always good to have a slump test and air test done. Along with the thin concrete, most guys like to add more water to make it easier to work, but that means weaker concrete. The tests make sure the concrete is within acceptable limits.

2. 12 tons of sub base is fine and dandy, but sub base is actually estimated in CY not tons. He might have screwed you on that alone. The tons mean nothing. Do you know how deep the sub base goes? That could be a reason why. And the most glaring reason is they didn’t compact it enough.

the reasons why concrete (especially new) cracks: 1. Poor concrete material, 2 not thick enough, 3. Subbase isn’t thick enough 4. Subbase wasn’t compacted enough.

1. 5” is not necessarily an issue, but it’s a random depth. 4”, 6”, 8”, etc. are standard depths.

2. Crushed aggregate base compacts at the rate of 2 tn/cy. So the tonnage does matter as long as you know the area.

[ECobb91]

1. 5” is not necessarily an issue, but it’s a random depth. 4”, 6”, 8”, etc. are standard depths.

2. Crushed aggregate base compacts at the rate of 2 tn/cy. So the tonnage does matter as long as you know the area.

5” is below standard depth for driveways. AASHTO, NYSDOT, and ACI all recommend the minimum concrete depth to be 4” for sidewalks, 6” for driveways, 8” for commercial driveways. That 1” makes a big difference especially if they used class D.

the compaction test is in PSI. So yes you could say tons per CY. However that measures the amount of force applied to the area, as in its compacted 1 Ton load per CY, not 1 ton of stone in a CY spot. Also, all aggregate is different depending on the grade and type. Select granular fill is compacted to a different standard than type 1, 2 or 3. So the contractor might have placed 12 tons of stone, but the depth is inadequate. Or it’s adequate depth but not compacted enough. The issue is the contractor told the OP they used 12 tons of subbase. They did not say it was compacted to so the OP can see if it was compacted properly. Every contractor bids a job in CY, and is paid for in place, after it meets standards.

[grout-scout]

Some of y’all should never come to Houston and buy a house. 100% of house slabs and driveways will have cracks similar to OP’s picture. Most within first 5 days.

Lol, that’s what I wrote earlier too. They obviously don’t do it even close to right down here.

[bassbuck]

I would have them put some saw cuts in the slab to help control future cracking.