Measuring earthwork excavation for RA bills

Unit of measurement

Earthwork in excavation for foundations is measured in cum. Excavation is measured as the net volume of the pit or trench, taken from the drawing dimensions and the levels recorded before and after digging.

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 and breadth of each pit or trench at the bottom, as shown on the foundation drawing, plus any working space the contract allows.
• Depth from the ground level recorded before excavation (the original ground level, taken jointly) to the bottom of the excavation.
• Depth in lifts where the BOQ pays separately by lift, for example up to 1.5 m and each further 1.5 m.
• Soil class for each part of the depth (soft soil, hard soil, soft rock, hard rock), where the BOQ prices them separately.

Standard deductions

• No deduction for the volume of small roots, boulders or pipes found in the excavation unless the contract says otherwise, as per the contract's mode of measurement and the relevant part of IS 1200.
• Slope or extra width cut for the contractor's convenience is not paid unless the drawing or the contract allows it.
• Rock is measured separately, usually by stacking or by cross-sections, and is taken out of the soil quantity so the same volume is not paid twice.

Worked example

Ward office building, foundation excavation in all soils, lift up to 1.5 m. Pit sizes include the working space shown on the drawing.

Row by row: Footings F1, 6 x 2.4 x 2.4 x 1.5 = 51.84; Footings F2, 4 x 2 x 2 x 1.5 = 24.00; Wall trench, grid A, 1 x 18.5 x 0.8 x 0.75 = 11.10.

Total: 51.84 plus 24.00 plus 11.10 = 86.94 cum. Deductions are entered with negative nos, so they reduce the total in the same column.

Common disputes

• Original ground levels were not recorded jointly before digging, so the depth cannot be proved after backfilling.
• Working space is claimed wider than the drawing or the contract allows.
• Soft rock is claimed where the client's engineer classified the strata as hard soil.
• Excavation below the founding level, dug by mistake, is claimed as extra depth.

Recording it in Tatha Vastu

Record the original ground level as a dated, photographed entry before excavation starts, signed off in the site app by both sides. Each pit is then an entry with nos, L, B and D, split by lift and soil class, and the quantity rolls into item 1.1 of the abstract.

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.