Cracks in concrete base

garv123

Got 8m of 30N concrete poured for a 9x6m shed base yesterday.
Concrete arrived at 11am.

When I arrived home at 6 the lads who did the job were gone and the concrete was full of big cracks. They came back when I rang them and they came back for a look and said it there was nothing they could do about it because of the hot weather and strong wind that was there all day, and it was perfect when they were leaving.
They tell me that structurally the concrete is perfect and that they'll put levelling compound on top to hide the cracks.

What do people make of that option as a fix?

listermint

Best off on the construction and planning forum I would say.

Personally I would not be happy with the job. Yes it's hot but bad mix or not wetting it down . Should have been covered over too with some cloth or other material to keep the sun off.

Lumen

Is there a DPM under it?

garv123

listermint wrote: »

Best off on the construction and planning forum I would say.

Personally I would not be happy with the job. Yes it's hot but bad mix or not wetting it down . Should have been covered over too with some cloth or other material to keep the sun off.

Mix is from roadstone, I reckon they should have spent longer minding it instead of fecking off to another job. They'll charge for a full days work anyway :rolleyes:

garv123

Lumen wrote: »

Is there a DPM under it?

Yup, 1000g Polythene between the 804 and Concrete.

TimHorton

garv123 wrote: »

Got 8m of 30N concrete poured for a 9x6m shed base yesterday.
Concrete arrived at 11am.

When I arrived home at 6 the lads who did the job were gone and the concrete was full of big cracks. They came back when I rang them and they came back for a look and said it there was nothing they could do about it because of the hot weather and strong wind that was there all day, and it was perfect when they were leaving.
They tell me that structurally the concrete is perfect and that they'll put levelling compound on top to hide the cracks.

What do people make of that option as a fix?

Should have been covered - Listen to a Civil Engineer explain why https://youtu.be/DSzgFLmDsx4?t=486

Calahonda52

should have been covered with hessian and kept wet until late evening
https://www.irishconcrete.ie/wp-content/uploads/2017/01/ICF-Guidelines-for-Hot-Weather-Mar2012.pdf

ted1

They failed to follow the suppliers guidelines. I’d get them back to fix it.

https://www.roadstone.ie/wp-content/uploads/2019/10/RS-Concrete-in-Hot-Weather.pdf

Protect concrete against moisture loss during placement and particularly curing period

garv123

What is the fix? Dig it all back out?? Cracks vary from 1 to 3 inches deep. From bits I can measure. 4.5 to 5 inches deep is what the concrete is

listermint

garv123 wrote: »

What is the fix? Dig it all back out?? Cracks vary from 1 to 3 inches deep. From bits I can measure. 4.5 to 5 inches deep is what the concrete is

Pretty much. There's no fixing that tbh.

Paullimerick

It's bad alright. They didn't keep it damp and it dried and expanded too fast. Disaster now I think from what I can see.

Bonzo Delaney

Is there at least mesh steel in it as a last hope saving grace

James 007

Bonzo Delaney wrote: »

Is there at least mesh steel in it as a last hope saving grace

Yes, they should of used a hessian mat like the below & have the slab soaking wet. Practically a 5min job would of prevented the cracking
https://www.safarigroup.com.au/chemicals/hessian-curing-blanket-18oz

Most likely they will tell him there is mesh in it, without seeing them doing the job, I wouldnt trust them unless your family member saw them put it in. The next question would be was the hardcore compacted, did he witness it.

They have made the dogs dinner out of it. Whats the shed to be used for, any traffic loading. Are you restricted to now taking it all out. Could you give them the option of taking it all out & doing it again which they wont want or a better option to slab over it again or are you restricted height wise.

I wouldn't be in a rush to paying them yet.

kadman

Would have thought wetting it down and covering during the curing period was the norm
for best practice putting down concrete.

You should not have to accept this, its poor workmanship at best, useless for purpose at worst.

I would not pay until it was rectified.

NickNickleby

I wonder could you complain to Roadstone about the cracking, maybe get them to come over and say bluntly "it wasn't laid/cured properly!" then its not a layman's unqualified opinion (as the builders will likely say).

Failing that, send them a photo/video and maybe they'll respond in an email, if they're not prepared to do a site visit.

Good luck with it.

garv123

To answer a few questions at once,

The guy who did it did 2 other concrete bases for dog runs, and footpaths for me, with no issues.

He's saying there's nothing he could do to stop that happening because of the weather, and wetting it more wouldn't have helped.

He still thinks that'll be structurally sound and the levelling compound will fix it all.

There's no steel in it and the 804 was put in by a different guy doing ground works with a digger.

It's a decent made shed with proper rsj structure, not like the steel tech stuff so the shed itself would be heavy enough sitting on the edges.
I'd want to be able to back in a trailer into the shed for a lawnmower, using my l200. So maybe not far off 3t weight.

Roadstone called out today to check it out. I haven't heard any verdict yet but I doubt they'll be taking any blame.

garv123

Few more pics

Stihl waters

garv123 wrote: »

To answer a few questions at once,

There's no steel in it and the 804 was put in by a different guy doing ground works with a digger.


Roadstone called out today to check it out. I haven't heard any verdict yet but I doubt they'll be taking any blame.

No steel, wtf were they thinking putting in 8 meters without steel, I'd be very surprised if roadstone entertained that for more than 5 minutes, especially if driver added water onsite, don't pay and make them take it out or clear them

10-10-20

What depth is the slab to take that weight?
A few control-joints mightn't have gone astray either.

Stihl waters

10-10-20 wrote: »

What depth is the slab to take that weight?
A few control-joints mightn't have gone astray either.

Its working out at 150mm going by the dimensions given

kadman

Roadstone would only be responsible for delivering the correct mix, and maintaining the proper
water to cement ratio. Meaning they did not water down the mix to aid working it.

Any lack of steel or wetting down to allow a proper cure is down to the groundworks team surely.

I cant see levelling compound being a lot of use to a slab requiring structural integrity.

listermint

garv123 wrote: »

To answer a few questions at once,

The guy who did it did 2 other concrete bases for dog runs, and footpaths for me, with no issues.

He's saying there's nothing he could do to stop that happening because of the weather, and wetting it more wouldn't have helped.

He still thinks that'll be structurally sound and the levelling compound will fix it all.

There's no steel in it and the 804 was put in by a different guy doing ground works with a digger.

It's a decent made shed with proper rsj structure, not like the steel tech stuff so the shed itself would be heavy enough sitting on the edges.
I'd want to be able to back in a trailer into the shed for a lawnmower, using my l200. So maybe not far off 3t weight.

Roadstone called out today to check it out. I haven't heard any verdict yet but I doubt they'll be taking any blame.

No ****ing way would be my response.

kadman

Roadstone wont be to blame, unless you can prove the mix is faulty.
And the only way you could prove this is with a test cube of the mix.
Was this taken ?

ted1

kadman wrote: »

Roadstone wont be to blame, unless you can prove the mix is faulty.
And the only way you could prove this is with a test cube of the mix.
Was this taken ?

Roadstone can say that they stuff was laid as per their guideline. Do the op can go back to the company that did shoddy work snd then to small claims court If required

kadman

In all fairness if you intend to place a proper shed constructed of structural steelwork, then you probably
needed a proper groundworks crew that would have experience of the slab requirements for this.

There is a world of difference between foot paths and dog runs than a shed for a portal frame construction
or similar.

I guess the op knows this now, and needs a remedy for this mess . Most likely being the removal of this slab,
and replacing it with a proper one. I cant see how you can place steelwork onto the edge of a slab
with no steel in its construction.

James 007

Laying structural RSJ columns at the edges may induce further triangular cracks in the slab. I cant understand why them guys didnt put a layer of A142 mesh 2 inches from the top surface into that slab. Introducing a control joint by cutting a horizontal joint at the 4m mark when the concrete reached 2/3 of its strength would of limited the cracking & induced a control crack at this point.

It sounds to me Paddy the builder didn't want to wait around & do that either. I guess the hot weather was to blame for him skiving off to get another job done

Regarding his footpaths how did he lay it, probably in max. 3m sections, therefore no cracking.

Best you tell the wife hold onto the purse for now, that slab wont take any traffic loading. Nothing to do with Roadstone man, Paddys at fault here

kadman

If bob the builder , or Paddy worked to the instructions of the op,
then he may not be responsible either. Its gonna be a tricky one.

If it was me I would ask the builder for a digout (excuse the pun)
and remove the slab foc. And employ a proper groundworks crew that
can do a proper slab for the steel shed.

OP may have to bite the bullet on this.

Calahonda52

garv123 wrote: »

To answer a few questions at once,

The guy who did it did 2 other concrete bases for dog runs, and footpaths for me, with no issues.

He's saying there's nothing he could do to stop that happening because of the weather, and wetting it more wouldn't have helped.

He still thinks that'll be structurally sound and the levelling compound will fix it all.

There's no steel in it and the 804 was put in by a different guy doing ground works with a digger.

It's a decent made shed with proper rsj structure, not like the steel tech stuff so the shed itself would be heavy enough sitting on the edges.
I'd want to be able to back in a trailer into the shed for a lawnmower, using my l200. So maybe not far off 3t weight.

Roadstone called out today to check it out. I haven't heard any verdict yet but I doubt they'll be taking any blame.

Without mesh and a deeper strip all round as shown here
https://www.pinterest.ie/pin/501307002262214091/
it wont work.
In addition it seems the 804 was not whacked.
not covering/wetting it in the sun is negligence.

It has to come out, IMO

kadman

If your slab is carry a structural RSJ built shed, then.

You need either an engineer to spec the slab for you, and to be there before the pour,
or during it,
Or,

A groundworks team that is fully briefed and knows what is going on it, and HAS INSURANCE,
should something go wrong. As they would/should have access to their engineer.

Stihl waters

kadman wrote: »

If your slab is carry a structural RSJ built shed, then.

You need either an engineer to spec the slab for you, and to be there before the pour,
or during it,
Or,

A groundworks team that is fully briefed and knows what is going on it, and HAS INSURANCE,
should something go wrong. As they would/should have access to their engineer.

An engineer is not needed for these type of jobs, any experienced ground worker would know what to do from previous experience

kadman

Stihl waters wrote: »

An engineer is not needed for these type of jobs, any experienced ground worker would know what to do from previous experience

I said either/or, read the post:)

garv123

Thanks for the replies lads, ye're all full of positivity :pac::pac:
Ye're right tho.

Roadstone have said it was down to drying too quick without the correct process for drying being followed. Which is good to hear in a way since the grounds works guy was saying there's nothing he could have done to stop it.

They're also going to talk to their engineer about putting 3" more concrete down on top of it. and I'll ask about adding steel too.

Now is the fun part of discussing cost for repairs with ground workers.

I spoke to one person whos over a large ground works company doing all concrete for large construction jobs and he seemed to think it was repairable with Sika concrete repair.

Calahonda52

More positivity:
was 804 whacked?
any mica/pyrite/ dinosaur bones in it?

kadman

Crack repair still offers nothing to fix the issue of no steel in the existing slab.

And the fact that you plan to place a structural steel building on it.

Putting additional concrete and steel on the existing may be an option. If you go this route
there is little difference in removing existing, and placing new.

I was never fond of a band aid fix personally.

listermint

kadman wrote: »

Crack repair still offers nothing to fix the issue of no steel in the existing slab.

And the fact that you plan to place a structural steel building on it.

Putting additional concrete and steel on the existing may be an option. If you go this route
there is little difference in removing existing, and placing new.

I was never fond of a band aid fix personally.

Also raises the levels so there is steps or slope for access. Not ideal.

funkey_monkey

If you are going 3" above I'd get them to go out at least 6" on all sides to fully encapsulate the bad slab.
However, there is not much more additional work in removing the cracked slab and doing it all again correctly.

They screwed up. Get them to do the job correctly at their own expense.

James 007

3 inches is not much in depth, screed territory really.

I would be inclined to go 5 to 6 inches depth. For a 6 inch slab put in a layer of A142 mesh 2 inches down from top surface easily done with suitable spacers. 30N concrete & this time ensure Paddy cures it currently using hessian rolls & water followed by a later sprinkling of water from yourself if the day is very warm, pay attention to the weather. Try & put in & induce a control joint at the 4m mark too.

Paddy has ****ed up so ensure he is paying for it.

funkey_monkey

From his first photo it looks like the slab is already flush with existing driveway. If he raised it up he would then need to tail a ramp out onto driveway.
Lifting the bad base would seem like the only option.

GreeBo

garv123 wrote: »

He's saying there's nothing he could do to stop that happening because of the weather, and wetting it more wouldn't have helped.

So he is admitting that the conditions were not right for the pour, but he went ahead anyway?
If it had been lashing rain and your wet concrete had run down the road what would he be saying?

Calahonda52

GreeBo wrote: »

So he is admitting that the conditions were not right for the pour, but he went ahead anyway?
If it had been lashing rain and your wet concrete had run down the road what would he be saying?

https://totalrailsolutions.co.uk/on-track-plant/hydraulic-breaker-hire/

James 007

funkey_monkey wrote: »

From his first photo it looks like the slab is already flush with existing driveway. If he raised it up he would then need to tail a ramp out onto driveway.
Lifting the bad base would seem like the only option.

In an ideal world yes lifting it up is probably best course of action as there is no rebar in it & it should be easy do. However sometimes you have to explore other avenues in difficult situations.

I cant tell the surrounding environs from the photos so the option of putting another slab over is still out there. Only the OP could comment further. Yes you would have ton ramp up but if you have the space & rotating your shed to have entrance face a different side to suit the environs it may work.

Holding onto the cash is key for now & wait for Paddys suggestions:rolleyes:

funkey_monkey

James 007 wrote: »

In an ideal world yes lifting it up is probably best course of action as there is no rebar in it & it should be easy do. However sometimes you have to explore other avenues in difficult situations.

I cant tell the surrounding environs from the photos so the option of putting another slab over is still out there. Only the OP could comment further. Yes you would have ton ramp up but if you have the space & rotating your shed to have entrance face a different side to suit the environs it may work.

Holding onto the cash is key for now & wait for Paddys suggestions:rolleyes:

That why I suggested going out at least 6" on all sides to encapsulate the cracked screed.
If there was just one issue then you could compromise a solution. However, just too many issues: cracking, no rebar, need for ramp with additional pour.

Definitely keep the hands in the pockets until a solution is offered from builder.

kadman

Playing devils advocate here,

If the op engaged the bob the builder guys, knowing their experience, or lack of.

And they carried out the work, under OP direction.

Then pockets may have to be open a tad.

I think we are all assuming, me included, that bob the builder was out of his depth.

What if the OP knew this, and said...sure go ahead it will be grand.;)

Wildly Boaring

Did the OP direct Bob to leave site on a sorching day after pouring concrete and do nothing to cure it?

Bob knew enough to try to blame the weather.
Pity he didn't know enough to Google what yo do about it.

Even without hessian he could have watered it with a garden hose.

James 007

kadman wrote: »

Playing devils advocate here,

If the op engaged the bob the builder guys, knowing their experience, or lack of.

And they carried out the work, under OP direction.

Then pockets may have to be open a tad.

I think we are all assuming, me included, that bob the builder was out of his depth.

What if the OP knew this, and said...sure go ahead it will be grand.;)

In normal circumstances you would have to assume that the client the OP does not have the knowledge or knowhow or experience with regards to construction. The previous OP posts tell me this is the case.

My guess is Paddy could be a smallish contractor cutting corners & running off to the next job, making hay while the sun shines. I'd be having the wife or partner playing the bad cop on this one for now & holding onto purse strings. Paddy will have to come back with a proposal & work it from there

kadman

Like I said, devils advocate.:D

We are all making assumptions on what took place, where as in reality the only one who knows
is the OP.

What we know is that it will need fixing.

Anything else, as Perry Mason says, is pure speculation;)

MeSeeksAnswers

1: The guys that laid a slab for anything larger than a small patio without steel reinforcement are idiots.

2: The guys that laid a slab for anything larger than a small patio without making sure it stayed wet for a few days are idiots

3.a: 1 & 2 are irrelevant to the OP. Cash is king here— if the OP is holding it and the idiots want it more than they want to avoid making good their ****ty work then he's sorted. If the idiots are already holding the cash and abandoning their ****ty work won't significantly inhibit the flow of more cash in their direction, he's basically screwed.

3.b: If the idiots most of their business off word of mouth etc, simply threatening to tell everyone he meets that they're incompetent might get a result for the OP. Relatively rare way for a company to get most of their cash flow these days, but still has potential.

4: If you paid the guy in cash, report him to Revenue & Social Welfare on general principal for trying to screw you.

kadman

I forsee this floating off into a whole other thread with endless assumptions.

To keep it on track I would be interested to know if roadstone engineer mentioned
has managed to come up with a solution to the op's issue.

garv123

Just an update. bob the builder does foundations for houses and other buildings on a regular basis. not out of his depth for a slab this size at all.

lots of people throwing assumptions around, getting a bit out of hand really.

I've contacted 3 other professionals working with concrete every day, and the guy who made the shed, and they have all said they would not be concerned about the cracks.

and they all said steel isn't needed for 100-120mm concrete base for a shed that size.

Now the fun bit starts for me, deciding who to believe and what to do..

Wildly Boaring

garv123 wrote: »

I've contacted 3 other professionals working with concrete every day, and the guy who made the shed, and they have all said they would not be concerned about the cracks.

and they all said steel isn't needed for 100-120mm concrete base for a shed that size.

When you say professionals you mean concrete guys or engineers.

I'm a chartered structural engineer and I would be concerned about those cracks.

Your photo with the tape shows cracks in excess of 2mm. Unacceptable without further investigation.

As a rule of thumb 1mm max on a ground bearing slab.
That 1mm would need to be shown to be surface shrinkage cracking. Any crack going completely through or tending toward completely through the slab is unacceptable.

As to the "steel". I'm assuming you mean rebar.
If the shed is designed to be self supporting then I agree rebar not required. Concrete is very strong in compression. To take self weight of a structure none is required.

But
1. If the concrete is acting as part of shed structure I would expect to see a design for required rebar.
2. On both cases the weight of your usage and planned usage is far more important. Any heavy usage would require a design.
3. The compaction of the fill under and the condition on the formation is very important. If you expect concrete to work in compression the formation layers must be adequately compacted. This cracking may worsen if the stone was not compacted

MeSeeksAnswers

garv123 wrote: »

Just an update. bob the builder does foundations for houses and other buildings on a regular basis. not out of his depth for a slab this size at all.

........

I've contacted 3 other professionals working with concrete every day, and the guy who made the shed, and they have all said they would not be concerned about the cracks.

and they all said steel isn't needed for 100-120mm concrete base for a shed that size.

.....

A few points here.

The first is that regular news items for more than a decade about tens of thousands of properties with severe defects related to pyrite, mica, and fire safety should be sufficient evidence for anyone that the mere fact that someone has done a lot of work in the construction industry (or any particular part of it) should not be taken as irrefutable evidence that they are competent in what they do, and don't cut important corners to save time & effort.

I'm reasonably confident that any construction professional reading this could think of highly qualified & long experienced incompetent idiots who cut important corners all the time because they couldn't be bothered... (for the record, I'm not a professional- just a nerd with an interest)

Secondly, the shed guy presumably wants you to pay him (a balance, or possibly up full), and as soon as possible. A dispute on the slab poured, and the delay caused by necessary remedial works, will mean he has to hold on to an otherwise worthless load of steel which he has already paid for (or perhaps is in debt for) for longer without getting the cash for it. At the very least I'm guessing it's occupying limited storage space somewhere. His advice (correct or otherwise) supports you following a course of action which directly benefits him: he can't be considered impartial.

Pretty sure none of the people here giving their opinions are expecting it to have any impact on their finances.

Thirdly, maybe the soil/hardcore etc under the slab will never shrink & leave voids under the slab, and maybe the shed and anything in it will never have to rely only on the tensile strength of 4 inches of concrete for support. Tensile strength which is normally only about 10% of compressive strength. And the cured compressive strength will likely have been greatly reduced by around 1/3 because it wasn't cured properly. And maybe the fact that the deep cracks which have already further weakened the tensile strength of the slab will therefore never be an issue.

How much money are you spending on the shed altogether? How much extra would it cost to fix it in a few years time instead of now? Are you willing to bet the difference on a whole bunch of maybes?

Finally, steel reinforcement is cheap. Like 12 square metres of 6mm mesh for under €50 and €7.50 for 6m of half inch bar cheap— you would have only needed to spend an extra €250 or so in materials to reinforce the perimeter with half inch bar and the rest with quarter inch mesh.

You've probably already dropped a grand on the slab and are planning to drop several more on getting the shed in place. Would the extra €250 make or break this project?