Loose volume and compacted volume are not the same number
Here is something that catches people out job after job, and almost nobody explains it at quote time.
When you order road base, you order loose material. It arrives loose, it gets spread loose, and it looks like plenty. Then you roll it. Once it is compacted, that same material takes up noticeably less space than it did loose.
So the volume you paid for and the volume you end up with in the ground are two different numbers. Not because you were short-loaded, but because compaction is physics. Air gets squeezed out and the material tightens up. If you planned your order around the finished, compacted volume and did not add anything for compaction, you will come up short. Every time.
How much does road base compact
It depends on the material, the moisture and how hard it is rolled, so treat these as working figures and confirm with your supplier or engineer for a critical job.
That means to end up with a given compacted volume, you need to order more loose material than the hole appears to need.
A worked example
Say you need a compacted pad 20 metres long, 10 metres wide and 150mm thick.
| Step | Working | Result |
|---|---|---|
| Finished compacted volume | 20 × 10 × 0.15 | 30 m³ |
| Loose volume needed (20% loss) | 30 ÷ 0.8 | 37.5 m³ |
Order 30 and you finish 20 percent short, back on the phone for another load, holding up the crew. Order around 37 to 38 and you finish on the money.
Why this matters for your budget, not just your day
A shortfall is not just an annoyance. It is a second delivery fee, a crew standing around, and a program that slips. On a tight site those cost more than the material.
It is also why some jobs seem to eat more road base than the plan allowed. It is not always waste or theft. Often it is compaction that was never factored in at quote time.
The right way to quote it
A supplier who knows the job should ask whether your volume is loose or compacted before they quote, and should tell you the compaction allowance for the product they are supplying. If nobody mentions it, ask. It is the single easiest way to stop a job coming up short.
At NXT Quarry we quote on the finished result you need, compaction included, so the last load lands close to exactly what the job called for. NXT Control forecasts your order’s final delivered volume as it runs, so you are not guessing at the end. See our road base and crushed rock range.