Estimating, Costing and Documentation
This domain tests quantity take-off, rate analysis, and the paperwork a contractor must produce.
Core rules and concepts
- Measure in the correct unit: pipe runs in metres, fittings in numbers, excavation and concrete in cubic metres, painting and waterproofing in square metres, fixtures in numbers. State the measurement rule you used.
- A bill of quantities lists description, unit, quantity and rate. Rate analysis builds the rate from material, labour, tools, wastage, overhead and profit.
- Allow about 5% wastage on pipes and 2–5% on fittings; include lead and lift, scaffolding, cutting and making good.
- Documents: measurement book, BOQ, quotation, work order, running bill, invoice, completion certificate. A quotation is an offer; an invoice is a demand for payment after supply.
- Rates follow the prevailing PWD schedule of rates with a percentage above or below, plus GST as applicable to the contract.
Worked example
30 m of 25 mm GI medium pipe at ₹180/m, 18 fittings at ₹60 each, labour 15% of material, overheads and profit 15%. Pipe = 5,400. Wastage 5% = 270, giving 5,670. Fittings = 1,080. Material total = 6,750. Labour = 1,012. Sub-total = 7,762. Overhead and profit = 1,164. Total ≈ ₹8,927. GST is then added on the total. Reasoning: wastage applies to material, labour applies to material value, and profit applies last.
Traps that cost marks
- Forgetting wastage, lead or lift.
- Mixing units - pricing fittings by the metre.
- Quoting without a site visit.
- Omitting GST or the terms of payment.