Estimation happens before the job starts and answers one question: how much money will this building need? Quantity surveying is what happens after — measuring what was really built, certifying what gets paid, and keeping the spend inside the estimate.
Every downstream decision on a project — procurement, subcontract packages, material ordering, interim payment certificates, the final account — is built on the quantities. If the take-off is wrong, nothing after it can be right.
The working sequence is always the same: read the drawing set, register the revisions, measure element by element, record the assumptions next to the measurement, and only then price it. Measuring from a superseded drawing is the single most expensive mistake in the trade.
Remember on site
- Estimation plans the cost; quantity surveying controls it.
- Never take quantities off an unapproved or superseded drawing.
- Write the assumption beside every measurement — you will be asked to defend it.
Check yourself
What is the primary output of a quantity surveyor's take-off work?
Which activity is squarely within a QS's role?
A QS does NOT decide which of the following?
What does 'cost control' mean in a QS's daily work?
Which document records day-to-day measurement of work done on site?
In a variation (extra item), what must the QS establish first?
Rate analysis primarily builds up a rate from which components?
Who typically decides the reinforcement design of a footing?
What is an 'abstract of cost'?
Why is accurate quantity take-off important before tendering?
A QS reviewing a contractor's claim for extra earthwork should first check what?
Which of these is outside a QS's control but affects the BOQ quantities?