New concrete not as flat as I expected...

[Vintage Veloce]

So my new 25' x 21' concrete foundation is in. Overall, it is fairly level, as I requested.

However, there are areas that are not very flat. I know this is a manually done floor, so it won't be perfect, but how flat should I expect?

I put a 6' straight edge down and there are some areas that are more than 1/2 inch high or low.

We did use 3500 PSI concrete, so it didn't flow much, maybe there just want much "self leveling" I know the concrete finisher was nervous about getting it all done before it hardened.

Is this just what I should expect? Should I complain? I'd been thinking I might want to put tile in someday, I imagine this much wavy-ness might be a problem. But at this point what could be done? Could we pour another 1" on top to try and level it?

C

 

[Strouty]

That is a lot in 6'

 

[lakeroadster]

How thick is the slab?

A 4" floor slab should have a thickness variation of no more than -1/4", +3/8", under ACI tolerances. That's a total allowable variance of 5/8".

 

[Strouty]

I thought the OP was saying that it was from 1/2" low to 1/2" high in 6' span. That would be an inch variation, unless it was all one direction for a specified slope then I would think that was a lot, especially if it is fresh concrete. As it cures it could become even worse.

 

[LXCam]

That's unacceptable. Did they screed the pour? or just bullfloat it?

Wait, let me take a guess at this. They only bullfloated it in one direction?.

BTW a typical standard is 3/16" between two points 10ft apart. 1/2" within 6 is a skateboard park.

 

[Strouty]

When I do tower foundations, I keep closer tolerances and I am usually burying them underground.

 

[brownbagg]

standard quality is 1/8 inch in ten feet

 

[Vintage Veloce]

They had a long aluminum flat thing that they pulled across the floor following the pumper, isn't that the screed? Then they bull floated a couple directions, and then they hand finished it while riding on aluminum skis.

The worst spot seems to be a high spot, maybe a bit more than a 1/2" high. You can put the 6' straight edge across it, and both ends would be about 1/2" above the concrete. Or you could push down one end, and then the other would be an 1" above the concrete. Kind of like a teeter totter.

C

 

[LXCam]

Flood your slab and take a picture. Since they did screed it and ran the float both directions I wonder if they just mounded up the cream or is the entire slab wavy?.

 

[Strouty]

How fresh is it? Maybe they could power trowel it if it is still green enough.

 

[Vintage Veloce]

It was poured last Monday and we start the walls tomorrow morning. So it's a week old.

This is the worse illustration. I'm holding the straight edge down on one side of the high spot, so the other end is elevated. You can see the 6' straight edge is about 1" up on the far end.

The rest of the 21' x 25' pad is better, this is the worst spot.
C

 

[Strouty]

I guess you can make a Koi Pond in the middle of the floor?

 

[RivennHewn]

Outline the problem area w/ chalk. Figure out how much area you have a problem with.

Rent a diamond stone terrazzo machine for a day and grind it down.

Will leave a smooth, exposed look but if you're going to epoxy/paint/ or tile it anyway- no problem.

From what I see, I would not accept it.

 

[carcajou]

High is relatively easy to remedy. Even an angle grinder and concrete grinding disks will repair that. I would expect the contractor to at least take down the high spots.

 

[katmat]

If it is only at one spot, you could core drill a hole the size of a floor drain & put a drain cover on it.

 

[bczygan]

What are the specifications in the contract?

You do have a contract with specifications....right?

Bill

 

[ishiboo]

If it is only at one spot, you could core drill a hole the size of a floor drain & put a drain cover on it.

Yeah... Installing a floor drain at the highest spot on the floor will leave great results

 

[LXCam]

That's ridiculous, is this guy a licensed contractor or were these the Home Depot weekend warriors. From your description sounds like he let the mud get away from him and didn't work it in time. Were you there? Did they start using a lot of water to help bring the cream up when they started troweling it?

 

[Strouty]

It may be the picture, but it looks like it curls up on the edges too. Anything can be fixed, all it takes is time and money.

 

[Vintage Veloce]

I went and pulled the video from my time lapse camera (love that thing).

Video of the pour and finishing here, 1 frame per minute.

Looks like the only bull nosed in one direction.

 

[Roddyo]

It looks like they screeded one end the then screeded the other wet screeding what they screeded first.

Laymans terms. Is this hump about 10 feet from one end where they over lapped while screeding the floor?

 

[Vintage Veloce]

It was just dark enough that I could use my laser level out there. Much of the garage is within an 1/8". Certainly most is within +/- 1/4" in the height around the garage. There is that one area that goes to - 1/2 that I illustrated with the straight edge above.
While I don't love it, I'm can probably be OK with this.

I have no interest in any coatings. But I could imagine polishing it or maybe tiling it some day.

If I was going to make the floor flatter now, how would I do it? Can you pour another 1" on top to level it and not have that top layer crack off in 10 years? Or can you get guys who can grind and polish the whole thing to +/- 1/8" better?

C

 

[pmiranda]

Like a couple guys already said, if it's just a high spot, that can be ground down and you'll be in good shape.

 

[chief ben]

We had our welding shop floor put down 22 years ago and 6 inch thick, and fiber glass in it,
26 feet X 50 Feet, I told the guy I want it slick as a baby *** and flat so when I lay out something to weld up I didn't have to shore up anything,
and he did a great job,
And it only cost $ 2000.oo bucks back in 1994 And still No Cracks in it.
I don't know what you payed, But I think you got a bad job done,

 

[chief ben]

You can't pour a 1 inch on top of that it will crack up and be a mess to clean up later, Oh by the way what was the cost ?

 

[Cyberbear]

1" difference in floor level is a LOT, and will require a lot to fix it. They make a floor leveling compound that is cement based that is often used by the floor covering trade. I had it used in a bathroom that had a rough and un-level floor. They came in and mixed the self leveling compound to a soupy consistency and simply poured what was needed to reach level all over. You may need to have the high spots ground down before the compound can be used.

 

[lakeroadster]

BTW a typical standard is 3/16" between two points 10ft apart. 1/2" within 6 is a skateboard park.

standard quality is 1/8 inch in ten feet

What "standards" are you guys referring to? To be a "standard" it needs to be from a recognized authority (such as ACI) and be adopted and recognized. The other option is simply numbers written into your contract with the contractor... as Bill eludes to.

What are the specifications in the contract?

You do have a contract with specifications....right?

Bill

 

[LXCam]

That time lapse is cool. They sure had enough guys to not have that happen. All it comes down too is the guy bull floating didn't do his job correctly. Had he gone both directions he would have caught that high spot. Basically they did everything ok, they just aren't very good. Hell the finisher would have felt that hand troweling but by that time there isn't too much he could have done to correct it. I'd suggest if you can live with the look to just grind it flat.

 

[cshield09]

1/8-inch in 10 ft is actually reeeeeally flat. Doesn't help the OP much, but the ACI 117 commentary describes a 1/8" in 10 ft as "superflat", corresponding to a FF50 floor flatness when tested using the F-number system that is much more commonly used in commercial construction, at least in my limited experience/area of practice.

TL;DR - 1/8" in 10 ft shouldn't be specified for general construction because it's a really, really flat slab.


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[Vintage Veloce]

Just for info, cshield, what is a typical standard for residential construction?

 

[mfrantz90]

That is terrible if you ask me... I did concrete for a living for a while. There is no way we would have left a job with it like that. Or let it set like that; I would be raising hell if I were you


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[Diesel Dan]

Just for info, cshield, what is a typical standard for residential construction?

Something I'd like to know as well.

I have never had a contractor tell me they will pour a rough, uneven slab and provide a smooth, flat and level floor. However I have seen contractors that state they can do flat/level work and deliver a rough and uneven product.

So far I've been through at least 6 contractors and none will state a figure. They ALL claim it will be flat/level and have had no complaints.

You want to scare them off fast? Ask if they have a 8' bull float.

 

[ADSR]

I wouldn't accept that and neither would my customers. That floor would be coming out.

 

[R. Deschain]

I have a 1/4" variance over 30' and I am not 100% happy. I have one 1/8" high spot and a low spot that is about 4' in diameter - about 1/8" below the perimeter walls. I can live with mine as it is a garage and wood shop, but I would be seriously making noise if I were you. At the minimum, I would demand that the high spots be ground flat.

 

[nadogail]

In the shipyards we used an epoxy compound to fill gaps between the foundations and machinery we were installing.

 

[bczygan]

I used to work for a design/build architect who wrote his specifications to benefit himself.

The wood door section said "Wood doors will be installed".

Hollow core luan?

Solid core oak?

It was all up to him when the time came to install.

And every change was an up-charge.

Would you sign a contract that said "I will build you a house", with no other definition?

Bill

EVERYTHING should be specified and performance specifications should detail every variation allowed. Admitted that nothing in the world is perfect, and you pay more when you try to get closer to that goal. But if you don't specify EXACTLY the level of fit and finish you expect, then you are liable to get anything.

And you then have no bargaining chips or legal recourse.

Bill

 

[bczygan]

And any contractor should desire complete specifications. Without them, he is doomed to have unhappy customers, and many lawsuits.

Bill

 

[Diesel Dan]

EVERYTHING should be specified and performance specifications should detail every variation allowed. Admitted that nothing in the world is perfect, and you pay more when you try to get closer to that goal. But if you don't specify EXACTLY the level of fit and finish you expect, then you are liable to get anything.

Again, here lies the issue.
How to spec a residential finish.

 

[Justanoldguy]

Just grind the high spots and be done with it.
Suggestions about ripping it all out is just CRAZY talk.
Mountain out of a molehill IMHO

 

[whiteg77]

I had my new slab grinded (ground??) by the contractor after I was complaining about the ridge marks from each float pass. It took him a day to complete and generated loads of dust but it was really smooth after the fact. Two complaints would be that the look is not uniform and i feel that maybe the surface is now softer than it should be. The texture of the surface is flat but I have loads of traction. I never worry about my family slipping. There are products that can go on post-grinding that re-harden the surface and take care of the dust but I opted for an epoxy. The epoxy lasted 7 months and peeled off. Now I don't care as much what it looks like. Good luck to you.


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