Roads · measured in cum
Measuring wet mix macadam for RA bills
WMM is measured as the compacted volume of each layer, from chainage length, design width and the compacted thickness proved by levels.
Unit of measurement
Wet mix macadam (WMM) is measured in cum. WMM is measured as the compacted volume of each layer, from chainage length, design width and the compacted thickness proved 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 between chainages for each stretch and layer.
- Design width of the base course from the cross-section.
- Compacted thickness of each layer, from levels before and after.
- Any extra width at curves, junctions and bus bays shown on the drawing.
Standard deductions
- Thickness laid above the design is not paid unless ordered.
- Areas over culverts and structures are taken out.
- Loose volume and wastage are not measured, as per the contract's specification.
Worked example
MIDC internal road, WMM 250 mm compacted in two layers, base width 7.00 m widening to 7.60 m at the junction.
| Location | Nos | L | B | D | Qty (cum) |
|---|---|---|---|---|---|
| Ch 0+000 to 0+250 | 1 | 250.00 | 7.00 | 0.250 | 437.50 |
| Ch 0+250 to 0+500 | 1 | 250.00 | 7.00 | 0.250 | 437.50 |
| Ch 0+500 to 0+620 | 1 | 120.00 | 7.60 | 0.250 | 228.00 |
| Total | 1,103.00 |
Row by row: Ch 0+000 to 0+250, 1 x 250 x 7 x 0.25 = 437.50; Ch 0+250 to 0+500, 1 x 250 x 7 x 0.25 = 437.50; Ch 0+500 to 0+620, 1 x 120 x 7.6 x 0.25 = 228.00.
Total: 437.50 plus 437.50 plus 228.00 = 1,103.00 cum. Deductions are entered with negative nos, so they reduce the total in the same column.
Common disputes
- Both layers are billed before the top layer is laid.
- WMM thickness is taken from GSB top levels that were never recorded.
- Width at junctions is claimed beyond the drawing.
Recording it in Tatha Vastu
Each layer is its own entry per stretch, so a stretch can show layer one billed and layer two pending. The levels of the GSB top are carried forward as the bottom levels of the WMM.
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.
Are layers billed separately?
They can be. Bill what is complete and accepted, and keep the layer number on the entry.
Which levels prove WMM thickness?
The top levels of the layer below and the top levels of the WMM, taken at the same grid points.
Is extra width at curves paid?
Where the drawing shows it, yes.