Roads · measured in cum
Measuring granular sub-base for RA bills
GSB is measured as the compacted volume laid, worked out chainage by chainage from the design width and the compacted thickness checked by levels.
Unit of measurement
Granular sub-base (GSB) is measured in cum. GSB is measured as the compacted volume laid, worked out chainage by chainage from the design width and the compacted thickness checked by levels.
The BOQ item description decides the unit and what the rate includes. Where the BOQ and this guide differ, the BOQ and the contract's mode of measurement win.
What is measured
- Length of each stretch between chainages.
- Width at the design cross-section, including any widening at curves or junctions shown on the drawing.
- Compacted thickness from levels taken before and after laying, at the grid the contract specifies.
- Layer number, where the sub-base is laid in more than one layer.
Standard deductions
- Thickness above the design is not paid unless ordered.
- Areas of culverts, chambers and structures within the stretch are taken out.
- Loose volume is not measured; only the compacted volume to drawing lines, as per the contract's specification.
Worked example
MIDC internal road, GSB 200 mm compacted thickness, carriageway width 7.50 m widening to 8.10 m at the junction.
| Location | Nos | L | B | D | Qty (cum) |
|---|---|---|---|---|---|
| Ch 0+000 to 0+250 | 1 | 250.00 | 7.50 | 0.200 | 375.00 |
| Ch 0+250 to 0+500 | 1 | 250.00 | 7.50 | 0.200 | 375.00 |
| Ch 0+500 to 0+620 | 1 | 120.00 | 8.10 | 0.200 | 194.40 |
| Total | 944.40 |
Row by row: Ch 0+000 to 0+250, 1 x 250 x 7.5 x 0.2 = 375.00; Ch 0+250 to 0+500, 1 x 250 x 7.5 x 0.2 = 375.00; Ch 0+500 to 0+620, 1 x 120 x 8.1 x 0.2 = 194.40.
Total: 375.00 plus 375.00 plus 194.40 = 944.40 cum. Deductions are entered with negative nos, so they reduce the total in the same column.
Common disputes
- Levels before laying were not taken jointly, so the compacted thickness is disputed.
- Width is claimed to the edge of the spill rather than the design width.
- Material is measured in trucks (loose) instead of compacted volume.
Recording it in Tatha Vastu
Entries carry the chainage from and to, so the strip chart shows which stretches are measured, billed and certified. Level sheets are attached to each stretch as the evidence for thickness.
Approved entries are locked, and a correction becomes a new version with its reason. See the measurement book, or use the measurement sheet template if you still keep the register in Excel.
Loose or compacted volume?
Compacted volume to drawing lines, unless your contract says otherwise.
How is thickness proved?
By levels taken before and after laying at the grid in the specification, preferably jointly.
Can a stretch be billed before the layer above is laid?
Yes, once it is complete and accepted. Record the acceptance with the entry.