How much does a concrete slab cost ?

[Spada]

Any concreters out there ?

At the moment, around my shed I have pine sleepers as retaining walls, and gravel around the shed. That was fine 10 years ago, but time has taken it's toll and the sleepers are rotten.

I'm planning to replace the retaining walls with interlocking blocks, but I'm contemplating going the whole hog and concreting around the shed where I have stone at the moment. There is roughly 90 Sq.M that I'd like to do, but I can't seem to find a guestimate as to what it would cost, and I don't like to waste tradies time getting a quote when I'm just tyre kicking at this stage.

Anyone on here have any knowledge with the cost of concreting ? Would it need to be 100mm thick, or would I get away with 75mm ( wont be driven on) ?

[kizza1]

Roughly $65 square meter is a rough guide for a shed slab

[Rumpig]

You'd have to give more info to get a proper cost amount from anyone ...
plain concrete or something different like exposed or a colour added? It makes a big price differance
any ground prep needed or are you doing all that?...will it need boxing or does the retaining wall act as all the boxing? Will a machine be needed for ground work (I'm guessing no?)
can you get a truck close up or is a pump needed?
I'm no concretor so no idea on price they'd charge, but to get a better cost idea those details would help.

[Moggy]

Roughly $65 square meter is a rough guide for a shed slab

FMD I hope thats not supplying everything. If it is can you come & do some for me. Up here you'd be lucky to get under  $130sqmtr 🤐

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[stabicraft]

My driveway cost 10K

That's prep and finishing.

But is is a double driveway with a thick slab.

[SEADOO]

I paid $2700 (cash job) for a 6x6m x 150mm thick slab for a carport.

I think it all depends on who does it.

[kizza1]

I'm not a concrete either I'm just going off what I have paid for a couple of slabs and what we pay for them at work.

As others have said it will depend on what extra work is involved.

$130 must be the mining tax at work again.

[Johnnos3003]

My Brother in law is a concreter here in Canberra and he charges $85 square meter for plain.

That includes form work for a 100mm slab, reo, hats and finishing. Providing the site has been preped/ leveled etc.   

[Rumpig]

I paid $2700 (cash job) for a 6x6m x 150mm thick slab for a carport.

I think it all depends on who does it.

every job is different...plain concrete you've got roughly $1100 we'll call it in your slab and 3 sheets of mesh at about $80 a sheet, so maybe $1400 in materials for arguments sake...that leaves $1300 to prep and pour it. 2 guys at say $400 a day is $800, just depends on ground prep time as to be one or 2 days they were there, and if a machine was needed as to how much they made themself on such a job.

[GBC]

$85 m2 should cover that sort of job unless you need a pump. If you need a bloke send me a pm mate.

[fergy]

Just paid 255 a cubic metre for conc
And 11 a square metre for prep, plastic, pour and finishing
I supplied the mesh f62?  Was 38 a sheet
So 9x8.5m. 110 mm thick $3360

[prodigyrf]

My Brother in law is a concreter here in Canberra and he charges $85 square meter for plain.

That includes form work for a 100mm slab, reo, hats and finishing. Providing the site has been preped/ leveled etc.

That would be common for a metro drive on slab and in a garage situation you'd be using Fortecon, F82 mesh on chairs (very important the mesh is near the top of the slab)and 25mpa concrete but for better wear characteristics I'd pay extra for 32mpa conc.

You asked about walk on paths then yes 75mm, no plastic film and F62 mesh and 25mpa concrete and the price should come down a bit from $85/sm but that depends on area and how fiddly the paving gets (cf say 6Mx6M double garage slab costing around $3000)

Again base preparation and conc pump can add to those figures and noone uses picks and shovels and wheelbarrows much anymore.

[Streetkid]

There is a local bloke in greenbank, he does heaps of work round the place and charged around the $50 a square met mark for basic work like paths an drive ways. He did our 100 square metre driveway for $5400 around six years ago and he did the bob cat work to prep it too as he has his own machine.

[Spada]

Thanks everyone for the feedback

You'd have to give more info to get a proper cost amount from anyone ...
plain concrete or something different like exposed or a colour added? It makes a big price differance
any ground prep needed or are you doing all that?...will it need boxing or does the retaining wall act as all the boxing? Will a machine be needed for ground work (I'm guessing no?)
can you get a truck close up or is a pump needed?
I'm no concretor so no idea on price they'd charge, but to get a better cost idea those details would help.

Plain concrete, nothing fancy.
Site prep will be done by me.
Only need to box a 4m edge, the shed slab and retaining wall will do the rest.
Will need to barrow into about 1/4 of the job (I'll provide 4 blokes with barrows), the truck will reach the rest.

I'll need someone with the skills to do the mesh and the pour.

I was thinking MP25 at 75mm thick, as it wont be driven on ? or should I go 100mm ? Theer will be a 20,000lt water tank on one area, maybe 100mm under that and 75mm everywhere else ?

There is a local bloke in greenbank, he does heaps of work round the place and charged around the $50 a square met mark for basic work like paths an drive ways. He did our 100 square metre driveway for $5400 around six years ago and he did the bob cat work to prep it too as he has his own machine.

Is that Les  from Equestrian Drive ?  I'm just trying to work out a guestimate for the cost. At $100 a metre, that'll work out to near 9k, so gravel it will be    (thats about double what I can afford)

[Streetkid]

Yep, les is a good old bloke, he won't mind coming round to give you a quote.

[Moggy]

Go a min 100mm, unless you like cracked concrete. Fot the tank area i would be upping it to 150mm to 1.0m outside of tank line, thats 20t on your slab. Put plastic underneath & then cure it for 7 days by covering with plastic and keeping wet, that should limit the cracking.
If your like me and hate cracked concrete, I'd go 32mpa

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[prodigyrf]

Go a min 100mm, unless you like cracked concrete. Fot the tank area i would be upping it to 150mm to 1.0m outside of tank line, thats 20t on your slab. Put plastic underneath & then cure it for 7 days by covering with plastic and keeping wet, that should limit the cracking.
If your like me and hate cracked concrete, I'd go 32mpa

Whoa there Neddy. All concrete cracks due to expansion and contraction which is why we put control joints in it and the mesh will minimise the cracking but more importantly prevent a shift in level when it does crack. Large slabs have diamond saw cuts whereas your 75mm paths come off the grooving trowel.

Yes thicker slabs are stronger but good concrete comes down to solid base preparation and appropriate expansion provision (ie allow an expansion joint between your path work and the garage slab) Thick slabs with high mpa concrete are useful say with heavy trandsport and forklifts etc, simply because the slab strength will bridge weak or soft spots in the base preparation, whereas a thinner slab could be just as effective on excellent base material. The evidence of that is many old style bathrooms and verandahs in my home town of Adelaide where we have extremely reactive clay soils. However with strip footings the old builders would fill in between with fine sand and then lay thin unreinforced terrazzo or coloured oxide concrete over it no problems. Why? Because fine sand is the perfect base for concrete PROVIDED it can't be eroded away, which of course it couldn't between the strip footings.

[prodigyrf]

Gee really strong concrete 
http://www.abc.net.au/news/2016-06-06/nsw-weather-large-waves-hit-collaroy-coast/7479846

[Pete79]

Not a concretor, but did just do my shed slab at home recently.
It's around 90m2. I did the prep work some weeks before we where ready to start with the shed. I paid for all the in slab items (mesh, bar, chairs, plastic, tape, etc) as well as the 15 cubes of concrete and the line pump for 4.5hrs. I called in a favor with our concretor from work and he did all of the work at mates rates.

All up it cost me $5,660.00
That put my per meter rate at around $63-$65.

But I asked my concretor if I didn't know him and was just someone off the street who asked him to do everything (prep, supply materials and pour) what would it cost.
He said for the same job he would have charged around $100 and for an average driveway (100mm thick and minimal prep) he usually charges around $80.




Then removed the form work halfway though and finished the pour.

[GBC]

If you only got one crack out of that you should be happy. Not a lot of engineering going on there. If you did actually manage to lose 15 cu in 90m2 I would expect to see more than double the amount of steel. That's an average thickness of just under 200mm which we use for heavy vehicle aprons on factories. Double mesh and 45 degree bar at every corner and offset is pretty standard at that depth. As are starter bars in that existing slab and rock surrounds along with a splash of Abelflex.

[GGV8Cruza]

And the funny thing with concrete is that you can plan where its going to crack, try and control where you want it to crack. Then the bloody slab does what it wants when it wants no matter how much reo, thickness of MPA of strength you put in the thing. After 25 years of playing with the stuff I still have no idea, well maybe a little.

The only way to stop the crack is a well designed fibre slab, they are the ducks nuts for holding up to anything you can throw at it.

GG

[Rumpig]

And the funny thing with concrete is that you can plan where its going to crack, try and control where you want it to crack. Then the bloody slab does what it wants when it wants no matter how much reo, thickness of MPA of strength you put in the thing. After 25 years of playing with the stuff I still have no idea, well maybe a little.

The only way to stop the crack is a well designed fibre slab, they are the ducks nuts for holding up to anything you can throw at it.

GG

i remember years ago our concretor at work attending a weekend seminar on how to stop concrete cracking....at the end of the weekend they basically told him, no matter what you do it'll still crack...lol...he was spewing he gave up a weekend basically for nothing

[Pete79]

If you only got one crack out of that you should be happy. Not a lot of engineering going on there. If you did actually manage to lose 15 cu in 90m2 I would expect to see more than double the amount of steel. That's an average thickness of just under 200mm which we use for heavy vehicle aprons on factories. Double mesh and 45 degree bar at every corner and offset is pretty standard at that depth. As are starter bars in that existing slab and rock surrounds along with a splash of Abelflex.

Hi mate, can you just expand on this for me?

As this is only a domestic shed slab, would you say double mesh would have really gained me anything?

Also, are you saying there is a lot of (or too much) concrete in this sized slab?

Not that I'm planning on doing this again any time soon, but always interested to hear from those with more experience on ways to improve things.
I do reserve the right to choose if I want to follow any such advice though.



We did pin into the existing slab with 16mm rods every 400mm. We didn't pin the rocks.
I went up to SL82 in the mesh from the SL62 that was called up on the engineering specs.

I was a bit rough with the m2 calcs I used in my first post. It's a bit over 90m2.
The thickening beam along one side ate up a lot of material and my beams under the shed walls are closer to being 400x400 then the 200x200 on the engineering plans.
Plus the overall thickness was a little stuff up on my side. I had worked on having a step around 200mm up from the slab to the house, but after I had done all of my prep work I realized I only wanted a 145mm step. So we just thickened the whole lot to match the step.
Also the concretor did the fall along the rocks a bit different to how I expected when I built the wall, so there is a good 250mm in front of the bottom corse.

[GBC]

It's all good, it's 'only a domestic shed slab'. In my world you have either not sanded up enough for the amount of reo, or haven't put in enough steel for a slab that was drawn at 200 nom plus thickening beams. I'm guessing it was drawn as a small (100-125 nom) slab and grew in depth but the drawings didn't change? The perimeter slab would have gone into tension where the shed slab was weighing on it, hence the cracking. A step like that with a cold join would be a Darnley with bond breaker bars or similar if an engineer was doing the steel inspections and certification. It's not necessarily better, just that it will give a guaranteed uniform outcome where you can guarantee the concreatures generally won't once the engineer has walked off site. Commercial concreting is a world apart. That's not to say yours won't be fine, just that if it was a commercial job with 15 cu at 200 the money I saved on steel would buy the boys a steak and a beer at the pub.

[Pete79]

Thanks mate.
Your assumptions are correct, it was designed to be a bit thinner and I didn't use enough sand to raise it up for the step.

The perimeter slab would have gone into tension where the shed slab was weighing on it, hence the cracking.

And I think that explains it.

Cheers.