How to read a concreting quote - and where the real differences hide

If you've ever collected three quotes for a driveway, you'll have seen the range. Someone quotes $X, the next person quotes 30% more, the third comes in 20% under. The natural reaction is to take the lowest. The right reaction is to figure out why they differ, because in concreting, the differences are almost never in the truck of concrete.

The things customers compare (but shouldn't, alone)

• Square metre rate. Useful as a sanity check, but every quote will use a different rate depending on what is included. Comparing rates between quotes is like comparing per-litre fuel prices between trucks of different size.
• Concrete cost. Roughly the same for every concreter - they buy from the same plants and pay similar rates. This is almost never the source of a quote difference.
• Pour day labour. Two or three workers for half a day. Similar across quotes.

Where the real differences hide

1. Base preparation

This is the single biggest variable. A cheap quote often says "prepare base" as a single line. A careful quote breaks it out:

• Strip topsoil to depth (and removal of that soil)
• Sub-base material (typically road base or crusher dust) - quantity in tonnes
• Compaction (plate compactor or roller)
• Levelling for falls (water needs somewhere to go)
• Form-up (timber or steel formwork)

A quote that skips most of this is cheaper because the work was skipped, not because the contractor is more efficient. Driveways poured on uncompacted base are how you get sunken corners in five years.

2. Reinforcement spec

Look for the exact reinforcement specified. Common terms:

• F62 / F72 / F82 mesh - sheets of welded steel grid. Higher number = thicker bars. A residential driveway should be at least SL72.
• Y10 / Y12 / Y16 rebar - reinforcement bar, sized by diameter in mm. Used for heavier-duty slabs or where mesh isn't suitable.
• Bar chairs - the little plastic stands that hold mesh off the base. Often missing from cheap quotes. If mesh isn't elevated, the slab isn't really reinforced.

"Includes reinforcement" with no spec is a yellow flag. Ask what mesh, and ask how it'll be elevated.

3. Concrete strength

Quotes should specify MPa. Driveways: 25 MPa standard. Commercial floors: 32 MPa or higher. A quote that doesn't specify, or specifies 20 MPa for a driveway, is using cheaper concrete - which costs the contractor 10-15% less and saves the customer nothing in the long run.

4. Joints, edges and finish

• Saw-cut crack-control joints at correct spacing (typically every 3-4 m)
• Edge tooling (a smooth radius edge that resists chipping)
• Finish type (broom, trowel, exposed aggregate, etc.) - explicitly stated
• Sealer if specified (decorative finishes usually need it)

5. Demolition, removal and tipping

If you're replacing existing concrete, the removal cost is significant. A quote that doesn't say whether demo is included is a quote that may bill you extra on the day.

What to ask before signing

If your quote is light on detail, three questions will reveal whether the contractor is cutting corners:

1. "What concrete strength are you specifying?"
2. "What reinforcement are you using, and how is it elevated?"
3. "How are you preparing the base, and what compaction equipment?"

A concreter who answers these clearly is one you can probably trust. A concreter who waves them off or gives vague answers is one whose slab might not be there in ten years.