Estimation, Costing and Quantity Take-off
This domain tests estimate types, measurement units, deduction rules and simple quantity calculations.
Types of estimate
Approximate (plinth area, cubical content, unit rate) for early budgets; detailed estimate from drawings measured to IS 1200; revised and supplementary estimates when scope or rates change.
Measurement units
Earthwork, PCC, RCC and brickwork in m³; plastering, painting and formwork in m²; steel in kg or quintal; doors and windows in numbers or m². For brickwork, no deduction is made for openings up to 0.1 m²; plastering follows its own IS 1200 opening limits.
Rate analysis and methods
Rate analysis = materials + labour + plant + overheads + profit, with contingency and work-charged establishment added. Long wall–short wall and centre-line methods quantify load-bearing walls; the centre-line method avoids double counting at junctions.
Worked example
A wall 3 m long, 3 m high and 230 mm thick has one door 1.0 × 2.1 m. Gross volume = 3 × 3 × 0.23 = 2.07 m³. The door area is 2.1 m², above 0.1 m², so deduct its volume: 2.1 × 0.23 = 0.483 m³, leaving 1.587 m³. At about 500 bricks per m³ this is roughly 794 bricks, with about 0.25–0.30 m³ of mortar per m³ of brickwork.
Traps
Forgetting door and window deductions, lintels and sills; mixing m² with m³; billing a design mix at nominal-mix rates; omitting reinforcement from RCC items; ignoring GST and the 1% BOCW labour cess.