Construction and infrastructure economics
Domain 1: Construction and infrastructure economics
This domain tests how a registered quantity surveyor turns design information, programme, market conditions and risk into defensible cost and value advice for buildings and infrastructure. Questions mix calculation with judgment: which cost basis, discount rate, contingency and appraisal rule to use.
Core rules and concepts
- Cost planning and estimating. Build estimates bottom-up from measured quantities and rates, or top-down from elemental or benchmark data. Keep base cost, escalation and contingency as separate lines; contingency is not a substitute for identified risk.
- Whole-life costing. Discount future maintenance, renewal and residual value to present value. Use real cash flows with a real discount rate, or nominal cash flows with a nominal rate - never mix them.
- Investment appraisal. For a single project, accept positive NPV. IRR is a screening measure; it can mislead for mutually exclusive projects, unusual cash-flow timing or scale differences. Use incremental NPV/IRR and benefit-cost ratio carefully.
- Infrastructure economics. Public infrastructure often involves externalities, affordability constraints and value-for-money tests. PPPs transfer specified risks, not all risk; VfM compares whole-of-life cost and outcomes against a public-sector comparator.
- Risk and optimism bias. Use reference class forecasting, risk registers and probabilistic ranges (P50/P80) rather than a single deterministic number. State the confidence level attached to a cost estimate.
Worked example
A road upgrade has a capital cost of 40m now, maintenance of 1.5m per year from year 1 to 30, a renewal cost of 8m at year 15, and a residual value of 5m at year 30. At a 5% discount rate, PV of maintenance is about 23.1m (1.5 × 15.37 annuity factor); renewal PV is about 3.9m (8 ÷ 1.05^15); residual PV is about 1.2m (5 ÷ 1.05^30). Whole-life PV cost ≈ 40 + 23.1 + 3.9 − 1.2 = 65.8m. If a rival option has a PV cost of 68m, choose the lower PV, provided risk and non-cost factors are comparable.
Traps that cost marks
Mixing nominal and real values; double-counting risk inside both contingency and discount rate; ranking mutually exclusive schemes by IRR; ignoring renewal or residual value; using payback for long-life assets; presenting a single cost without a stated basis, date or confidence level.