Estimation and Quantity Surveying
Domain overview
This section tests measurement, quantity take-off, rate analysis and BOQ preparation. The exam expects consistent units, correct deductions and a clear distinction between wet volume, dry volume and wastage.
Core rules
- Measure net quantities from drawings and deduct openings above the specified threshold; do not mix structural concrete and finishes.
- Rate analysis combines materials, labour, plant, overheads and profit; wastage and bulking are added where the code or specification requires.
- For nominal mixes, convert wet volume to dry volume using a factor such as 1.54 before applying the mix ratio.
- Keep contingency and price escalation separate from measured quantities; both are estimate allowances, not take-off items.
Worked example
A slab 5 m × 4 m × 0.15 m has wet volume 3.0 m³. For a 1:2:4 nominal mix, dry volume = 3.0×1.54 = 4.62 m³. Cement volume = 4.62/7 = 0.660 m³; at 0.035 m³ per 50 kg bag, bags = 0.660/0.035 = 18.9, so provide about 19 bags before wastage. Sand = 2/7×4.62 = 1.32 m³; coarse aggregate = 4/7×4.62 = 2.64 m³. Add wastage separately and state whether it is included in the rate.
Traps
Applying the mix ratio to wet volume, using 1 m³ per bag, double-counting wastage that is already in the rate, and mixing m² and m³ units in the BOQ.