Running-bill measurement: an undeducted gate, brick counts and three extra claims
A boundary wall for a cold-storage compound in Hooghly is being measured for the running bill. The wall is 20.0 m long and 2.0 m high above the plinth beam, 250 mm thick, in brickwork with cement mortar 1:6, and has one gate opening 3.0 m wide × 1.8 m high. The contractor has billed 10.00 m³ of brickwork at his quoted ₹7,200 per m³. He has added separate claims of ₹6,000 for scaffolding, ₹1,500 for curing water and ₹8,400 for 'extra wastage of bricks 10%'. Your accepted constants are 500 bricks per m³ of finished brickwork, 0.30 m³ of wet mortar per m³ of brickwork, dry-volume factor 1.33, cement at 1440 kg/m³ in 50 kg bags, and 5% allowance for brick breakage. The measurement book records the gate opening, but the bill does not deduct it. The client has already paid 75% of the billed amount as an advance and wants a final settlement this week.
1. Work out the correct net quantity of brickwork and state the deduction rule you are applying.
Read the worked answer
Gross volume = length × height × thickness = 20.0 × 2.0 × 0.25 = 10.00 m³. This is what the contractor has billed.
Deduction rule used in Indian measurement practice (IS 1200 / PWD method of measurement): openings in masonry larger than 0.1 m² in area are deducted; smaller openings, such as a small vent or a pipe hole, are not deducted because their volume is treated as negligible.
The gate is 3.0 × 1.8 = 5.4 m², far above 0.1 m², so it must be deducted: 5.4 × 0.25 = 1.35 m³.
Net brickwork = 10.00 − 1.35 = 8.65 m³.
Effect on the bill: the contractor has over-measured by 1.35 m³, which is 13.5% of the true quantity. At ₹7,200 per m³ that is ₹9,720 that is not payable. Note that the deduction is for the full thickness of the wall through the opening; the lintel over the gate is a separate concrete item and must not be hidden inside the brickwork rate. Check that the plinth beam and the coping are likewise measured as separate items, not included here.
2. Compute the bricks, cement and sand required for the corrected quantity, showing the reasoning chain.
Read the worked answer
Bricks: 8.65 m³ × 500 bricks/m³ = 4,325 bricks. Add 5% for breakage and cutting: 4,325 × 1.05 = 4,541, so order 4,550 bricks (round up; you cannot buy a fraction).
Mortar, wet to dry: 8.65 × 0.30 = 2.595 m³ wet. Dry volume = 2.595 × 1.33 = 3.451 m³.
Cement, 1:6 (one part cement to six parts sand, seven parts total):
- Cement volume = 3.451 / 7 = 0.493 m³
- Mass = 0.493 × 1440 = 710 kg
- Bags = 710 / 50 = 14.2 bags, so order 15 bags
Sand = 3.451 × 6/7 = 2.96 m³, about 3.0 m³ or roughly 105 cft.
Credibility check: the cement works out at 710 / 8.65 ≈ 82 kg per m³ of brickwork, that is about 1.6 bags per m³. That agrees with the usual thumb rule for 1:6 mortar, so the arithmetic is sound.
Reasoning chain to remember: wet mortar → dry mortar (× 1.33) → share by ratio → volume to mass (× 1440) → mass to bags (÷ 50). Always carry the check figure per unit; if you get 3 bags or 8 bags per m³, you have slipped a step.
3. Which of the contractor's extra claims are payable, and what is the net amount to be certified?
Read the worked answer
Test each claim against what the item rate is deemed to include.
- Scaffolding ₹6,000 - not payable. For a wall only 2.0 m high, all scaffolding and staging is included in the brickwork item rate (generally the rate covers staging up to about 3.5 m). Scaffolding becomes a separate measurement only for higher or special work, and only if the bill of quantities says so.
- Curing water ₹1,500 - not payable. Curing is part of the masonry item; the contractor prices it into his rate.
- 'Extra wastage 10%' ₹8,400 - not payable. Wastage is a risk carried inside the item rate, and the 5% breakage allowance is already built into the material computation. Besides, on an over-measured bill the contractor is already ahead.
Certified amount: 8.65 m³ × ₹7,200 = ₹62,280, less retention or adjustment for the 75% advance already paid, as per the contract.
Comparison: the contractor claimed ₹72,000 of brickwork plus ₹15,900 of extras = ₹87,900, against ₹62,280 actually due. Some ₹25,620 must be deleted - subject to a re-check of the measurement book figures. Issue the corrected measurement sheet, get it jointly signed, and record the reasons for each disallowed claim so that the same claims do not reappear in the final bill.