The gap a shovel actually saves you
Ready-mix delivered by the truck is the cheapest way to get concrete into a slab, full stop, the cost above is materials only, with no labour charge because the labour is you. For this slab that's a genuine saving of $500–$900 against calling a concreter, provided you (or a mate) can screed it level, float and edge the surface, and cut control joints before it goes off. Concrete gives you a working window measured in tens of minutes on a warm day, not hours, so that saving comes with a real skill and timing requirement attached: get the finish wrong and there's no redo once it cures.
What it actually costs
Same worked example as our concrete calculator: a 4 m × 3 m shed slab at 100 mm deep, 1.2 m³, 12 m².
| Option | What it includes | Cost |
|---|---|---|
| DIY, ready-mix delivered | Concrete only, you supply the labour: screeding, floating, edging, curing | $380–$480 |
| DIY, bagged (20kg premix) | Concrete only, hand-mixed, 130 bags for this slab | $1,170–$1,560 |
| Hire a concreter (supply & lay) | Concrete, formwork, labour, screeding and finishing, basic site prep | $900–$1,320 |
Hire figures are supply-and-lay quotes for a standard slab, not labour-only; DIY figures are materials only and exclude your own time, tools or any hire equipment.
Why bagged concrete is the expensive DIY option
The counterintuitive number in the table above is bagged premix. At 130 bags for this slab, buying by the bag costs more than just paying a concreter to supply and lay the whole job for you, and that's before counting your own labour, a hired mixer, or the extra day hand-mixing that many bags takes. Bags earn their keep on small pours: footings, post holes, a garden edge, anything under roughly half a cubic metre, where a ready-mix truck's short-load surcharge would otherwise eat the saving. Past that size, as our concrete calculator's own verdict already says, ready-mix wins on cost every time, and by this slab's size, it's cheaper than hiring a concreter too, not just cheaper than bags.
What the concreter's $900–$1,320 buys beyond the pour itself: correctly set formwork, any reinforcement mesh the slab's use calls for, falls graded for drainage, and a trowelled finish done inside concrete's short working window by someone who does it every week. For a shed base or garden slab with no load or drainage requirement, that's often money spent on insurance against a mistake rather than a necessity. For a driveway, a structural slab, or anywhere getting the fall or reinforcement wrong causes real problems later, it's the part of the job most worth paying for.
Common questions
Is it cheaper to DIY a concrete slab or hire a concreter?
DIY with delivered ready-mix is cheaper on materials alone, roughly $380–$480 for a 12 m² shed slab against $900–$1,320 to hire a concreter to supply and lay the same slab. That gap excludes your own labour, tools and the risk of a finish you can't redo once the concrete sets, which is what the concreter's price is largely paying for.
Is bagged concrete cheaper than hiring a concreter?
Not for a slab-sized job. 130 bags of 20kg premix for a 12 m² shed slab costs roughly $1,170–$1,560, more than the $900–$1,320 a concreter typically charges to supply and lay the same slab professionally. Bags only make sense on small pours under about half a cubic metre, footings, post holes, a garden edge, where a ready-mix truck's short-load surcharge would otherwise apply.
How much do concreters charge per square metre in Australia?
Around $75–$110 per square metre for a standard supply-and-lay residential slab, with a 2026 national average of about $92/m² (ServiceSeeking). Excavation, reinforcement mesh, difficult access or a decorative finish add to that base rate.
Does the same 'cheap-looking DIY option costs more than expected' pattern show up anywhere else on this site?
Yes, driveway surface choice runs into it too. Our gravel vs concrete vs pavers guide finds gravel is the cheapest driveway to install but the most expensive over a decade once its regular top-ups are counted, the same shape as bagged concrete costing more than hiring a concreter for a slab this size.
Sources
Hire-a-concreter pricing: ServiceSeeking, Concreter Prices in Australia for 2026 and ServiceTasker, How Much Does a Concrete Slab Cost. DIY materials cost and bag count: same Boral/hardware-retailer sourcing as our concrete calculator. All fetched July 2026.