Cracks in concrete base

garv123 · 23-06-2021 12:09pm

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 · 23-06-2021 12:24pm

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

kadman · 23-06-2021 12:28pm

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 · 23-06-2021 2:25pm

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 · 23-06-2021 2:59pm

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 · 23-06-2021 7:36pm

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 · 23-06-2021 8:04pm

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 · 24-06-2021 2:16pm

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 · 24-06-2021 7:01pm

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 · 24-06-2021 7:55pm

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 · 24-06-2021 8:36pm

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 · 24-06-2021 9:10pm

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 · 24-06-2021 9:14pm

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 · 24-06-2021 9:37pm

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 · 24-06-2021 9:57pm

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 · 24-06-2021 10:13pm

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 · 24-06-2021 10:27pm

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 · 25-06-2021 8:50am

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 · 25-06-2021 9:07am

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 · 25-06-2021 10:04am

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?

Stoner · 25-06-2021 10:34am

At the OPs request I'm closing this thread

It was a good read in parts, but generally if the person who opened the thread wants it closed, we'd close it.

Cracks in concrete base

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