Concrete slab tolerances

[Com_VC]

Hi got a slab done professionally. About 6 metres x 6 metres. Now the problem is it's not square. I measured across and it's about 30mm out in some places. Haven't done the diagonals yet.
<o></o>
Just wondering what sort of tolerance is allowed as I assumed it should be pretty much spot on or maybe 3-5mm out at max.<o></o>
<o></o>
I'm guessing now that it's all done there’s not a lot that can be done...<o></o>

[Calm]

I'm guessing now that it's all done there’s not a lot that can be done...<O

If you haven't paid for it there is probably a fair bit can be done, If you have paid for it i guess it depends on whether they want to do it.

[Cementer]

There's no tolerance for shonky work. It should be spot on or at the worst, say 10mm across the diags. No more than that for a 6x6.
But now that its done. What is the slab for, a shed or something? How critical is it? If it isn't too critical then maybe a dollar or too knocked off the price???

[DavidG]

Saw a small slab for a shed that was half a brick longer one one side.
Shonky was at work.

[peter_sm]

If I can get a 13 x 7 metre with diagonals only 5mm out, and widths only varying by 10mm out, then there should be at least that or better on a smaller slab

[Ivan in Oz]

If I can get a 13 x 7 metre with diagonals only 5mm out, and widths only varying by 10mm out, then there should be at least that or better on a smaller slab

Me thinks the 5mm and 10mm should be the other way round.

All Variances 'should' be less than 1/4" [6.35mm]

My 12M x 9M Slab was well within these,
Both,
Sides and Diagonals....................I'm Quite pleased

[peter_sm]

No that is correct. The corner diagonals were 5mm out, and the width varied by 10mm when measuring across the slab due to pressure exerted on the sides of the formwork. This created a 10mm'ish wiggle. The corners don't blow out or move, because they are, well corners.

As the slab had a stud wall on it, which has a small overhang anyway, such a small wiggle is irrelevant and unseen.

Me thinks the 5mm and 10mm should be the other way round.

All Variances 'should' be less than 1/4" [6.35mm]

My 12M x 9M Slab was well within these,
Both,
Sides and Diagonals....................I'm Quite pleased

[Com_VC]

There was a 60mm difference between the diagonals, it's all been sorted now, probably about 5mm out or so now.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" /><o></o>
<o></o>
Didn't end up paying the total amount. Will wait till the shed is erected.<o></o>

Thanks for the advice.

[Ivan in Oz]

No that is correct.
< SNIP >
due to pressure exerted on the sides of the formwork.

I believe many People do NOT realise how much Pressure can be exerted on the formwork.
That's why many Concreters have,
WHAT APPEARS TO BE,
AN EXCESSIVELY lot of Formwork Reinforcement and Stabilization.

Even MORE Pressure when the Concrete is Vibrated