There's a point where "just grab some bags" stops being the sensible choice — not because bagged concrete is bad, but because the labour and cost curve flips against it once a pour gets big enough.
| Job | Volume needed | Bags (25kg) | Better option |
|---|---|---|---|
| 6 fence post holes | 0.254 m³ | 28 | Bagged mix |
| 2.4m × 1.8m shed base | 0.432 m³ | 40 | Borderline, bagged still workable |
Both of these sit under the 0.5 m³ line, so bagged mix is the sensible call for either. Push past it — a larger base, a driveway section, a bigger footing — and 40+ bags becomes 60, 80, 100+: hours of mixing by hand or wheelbarrow-loads through a mixer, versus one ready-mix lorry showing up and pouring it in minutes.
Ready-mix sometimes costs more per m³ than the equivalent bags on paper — the real case for it above 0.5 m³ is time and physical effort. Mixing 60+ bags by hand across a single day is a genuinely demanding job; a lorry delivery isn't.
Rectangular slabs or round post holes — get the exact volume and bags needed, with the ready-mix flag built in.
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