Estimation, Costing and Quantity Surveying
What this domain tests
You must measure quantities from drawings, apply the long wall–short wall or centre line method, deduct openings, use correct units, and build a bill of quantities with rates.
Core rules and concepts
- Units: earthwork and concrete in m³, brickwork in m³, plaster and painting in m², steel in kg, doors and windows in numbers, water supply and sanitary lines in running metres.
- Long wall–short wall method: long wall length = centre-to-centre length + half width at each end (i.e. + one full width); short wall length = centre-to-centre length − half width at each end.
- Deductions: openings above 0.1 m² are deducted from masonry and plaster; no deduction for small holes.
- Costing: quantity × rate = amount; add contingencies, work-charged establishment and centage; abstract gives the total; rates come from the schedule of rates plus non-schedule items.
Worked example
Room 4 m × 3 m internal, 230 mm walls, height 3 m, one door 1.0 × 2.1 m. Centre line long = 4 + 0.23 = 4.23 m; long wall = 4.23 + 0.23 = 4.46 m. Centre line short = 3 + 0.23 = 3.23 m; short wall = 3.23 − 0.23 = 3.00 m. Long walls: 2 × 4.46 × 0.23 × 3 = 6.155 m³. Short walls: 2 × 3.00 × 0.23 × 3 = 4.140 m³. Total 10.295 m³. Less door 0.483 m³ → 9.812 m³. At ₹6,500/m³ the brickwork costs about ₹63,780.
Traps that cost marks
Using the inside length as the long wall; forgetting door and window deductions; mixing m² and m³ units; deducting small holes that need no deduction; quoting a rate without the schedule reference.