1.4 Ordering the right amount
Work out the compacted volume, add what the layer loses when it is compacted, convert to weight if the supplier sells by weight, and add a little for waste.
At a glance
- Volume
- Area × compacted thickness
- Compaction
- × 1.4 for crushed with fines, × 1.2 for sand, × 1.15 for washed stone
- Weight
- Loose m³ × loose density, about 1.5–1.6 t/m³
- Waste
- Add a little extra
Calculator
Uses the typical values below. Your supplier's own density figure is better if they have one.
Typical densities t/m³, dry
| Material | Loose | Compacted | Loose ÷ compacted |
|---|---|---|---|
| Sand 0–4 | ≈ 1.5 | ≈ 1.9 | ≈ 1.2 |
| Washed stone 8–16, 16–32 | ≈ 1.6 | ≈ 1.85 | ≈ 1.15 |
| Crushed with fines 0–16, 0–32 | 1.5–1.65 | 2.1–2.25 | 1.35–1.5 |
Step by step: a patio base
-
1
Work out the compacted volume.
A 20 m² patio on 150 mm of compacted 0–32: 20 m² × 0.15 m = 3.0 m³.
Measuring the area with a tape -
2
Add the compaction allowance.
Crushed with fines shrinks when compacted: 3.0 m³ × 1.4 = 4.2 m³ loose.
Loose heap and compacted layer -
3
Convert to weight.
If the material is sold by weight: 4.2 m³ × 1.6 t/m³ = 6.7 t.
A load on the weighbridge -
4
Round up and add a little for waste.
6.7 t rounds up to 7 t. Order a little more to cover waste.
The delivered heap
Specifications
Why loose and compacted differ
A loose heap is full of air gaps. Compaction pushes the small grains into the gaps between the big ones. A well-graded material with fines has the most to fill, so it shrinks most. Washed single-size stone has least to fill, so it shrinks least.
Compacted density
Highway agencies estimate compacted dense-graded crushed base at about 2.1–2.25 t/m³. The value in a real layer depends on the rock, the moisture and the compactor.
Rock type
Most normal aggregates have a specific gravity of 2.4–2.9, meaning a solid m³ of the stone weighs 2.4–2.9 t. Dense rock such as basalt is at the heavy end, so its heaps weigh more for the same volume. Ask the supplier.
Sources
- FHWA Federal Lands, earthwork design, Exhibit 6.1 A: dry sand 1535 kg/m³ loose, 1920 compacted; uniformly graded gravel 1600 loose, 1870 compacted; well-graded gravel 1645 loose; basalt 2935 in place
- WisDOT research report 0092-22-05, Table E2: dense-graded base 1.80–1.86 tons/yd³ compacted, expansion compacted to loose 34–52 %
- Iowa DOT design manual 1B-4: crushed stone base 140 lb/ft³ (2.24 t/m³) for estimating quantities
- WSDOT Geotechnical Design Manual, Table 10-1: sand 109 lb/ft³ loose, 129 compacted
- ACI Education Bulletin E1-16: specific gravity of most normal aggregates 2.4–2.9
- CEC (Government of India) glossary: at 5–8 % moisture, sand volume increases by up to 20–40 %
- Virtual Labs, bulking of fine aggregate: maximum bulking at 4–6 % moisture
Densities and loose-to-compacted factors are rounded from the sources above for planning, not design. Imperial figures use short tons (2,000 lb): 1 t/m³ = 0.843 tons/yd³.
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