Estimation, Measurement and Costing
Estimation, Measurement and Costing tests quantity take-off, measurement units, deduction rules, rate analysis and preparation of a simple bill of quantities. Expect brickwork in m3, plaster in m2, concrete in m3, reinforcement in kg and finishes in m2.
Core rules
- Measure brickwork and concrete in cubic metres, plaster and tiling in square metres, steel in kilograms, and linear items in running metres.
- Deduct openings according to the measurement rule; a common convention is no deduction for small openings below the specified threshold, but always state the rule used.
- Add wastage and shrinkage allowances separately; do not hide them inside the measured net quantity.
- Rate analysis separates material, labour, plant, overheads and profit.
- Keep measurements in a standard format so another person can check them.
Worked example
A wall is 4 m long × 3 m high with a door 1 m × 2.1 m. Gross area = 12 m2; door area = 2.1 m2; net plaster area = 9.9 m2. At Rs 250/m2, plaster cost = 9.9 × 250 = Rs 2,475. Add 10% overhead and profit = Rs 2,722.50. For brickwork, the same wall at 230 mm thick has net volume 9.9 × 0.23 = 2.277 m3; do not price it as 12 × 0.23 because the opening is excluded under the stated rule.
Traps that cost marks
Mixing units, forgetting wastage, deducting openings twice, or omitting labour from a rate are common. A low material rate can still give a high final cost if wastage and overheads are ignored.
Key points
- Brickwork and concrete: m3; plaster and tiling: m2; steel: kg.