Reasons concrete runs short
- Forms are deeper or wider than the plan.
- The base has low pockets that were not filled and compacted.
- Round holes bell out below grade.
- Some material remains in wheelbarrows, mixer drums, chutes, or tools.
Ordering buffer
Concrete Waste Buffer Guide
A waste buffer protects you from imperfect forms, uneven excavation, spillage, and finishing interruptions. The calculator lets you choose the percentage before it calculates the recommended order.
Typical buffer ranges
| Buffer | When it fits | Watch-outs |
|---|---|---|
| 5% | Simple formed slab, careful grade, professional crew, easy truck access. | Little room for measurement mistakes. |
| 10% | Common starting point for DIY patios, sidewalks, and small footings. | Still confirm supplier minimums and rounded load sizes. |
| 15% | Irregular excavation, post holes, slopes, hand-dug trenches, or uncertain base. | May over-order on very large clean pours. |
Reasons not to overdo it
Extra concrete still has to be placed, cleaned up, or disposed of. On larger jobs, a careful takeoff and supplier conversation may beat a large blanket buffer.
For ready-mix, ask how they round order sizes and what happens if you need a small balance load.