Estimation, Costing and Work Measurement
What this domain tests
Estimation questions test types of estimates, units of measurement, deduction rules, centre-line and long-wall short-wall methods, bar bending schedule, and rate analysis build-up.
Core rules and concepts
- Types: approximate (plinth area or cubic content), detailed, revised, and supplementary estimates; a detailed estimate needs drawings, specifications and a report.
- Units (IS 1200 practice): earthwork, concrete and brickwork in m³; plaster, painting, flooring and waterproofing in m²; doors and windows in m² or numbers; reinforcement in kg or quintals; pipes and cornices in running metres.
- Deductions for brickwork are made for openings exceeding 0.1 m²; in plaster no deduction is made for openings up to 0.5 m².
- Centre-line method suits walls meeting at junctions; long-wall short-wall method suits regular rectangular plans.
- Rate analysis adds material, labour, sundries, and contractors' profit of about 10%, with contingencies of 3-5% in the estimate.
- Bar bending schedule lists bar mark, diameter, shape, cutting length, number and total weight at 0.00618 d² kg per metre for steel.
Worked example
Materials for 10 m³ of brickwork in cement mortar 1:6. Bricks = 5000, plus 5% = 5250. Mortar at about 0.3 m³ per m³ of brickwork = 3 m³ wet, dry = 3 × 1.30 = 3.9 m³. Cement = 3.9 ÷ 7 = 0.557 m³ = about 16 bags; sand = 3.9 × 6 ÷ 7 = 3.34 m³. Multiply each quantity by its current rate and add labour to get the cost.
Traps that cost marks
Measuring painting in m³; deducting every small opening; forgetting the dry-volume factor; quoting steel weight without the 0.00618 d² factor; omitting contractor profit and contingencies from the abstract.