Quantity surveying is the profession responsible for managing the costs of construction projects — from the earliest cost estimates before a single brick is laid, through to the final account once the building is complete. A quantity surveyor (QS) is essentially the financial and contractual expert on a construction project, making sure the client gets value for money and the project stays within budget.
If you’re new to the subject, it helps to think of quantity surveying as sitting at the intersection of construction, law, and accounting — you need to understand how buildings are actually built, how contracts allocate risk, and how to track and control cost.
Table of Contents
ToggleWhat a Quantity Surveyor Actually Does
The role spans the entire lifecycle of a construction project:
- Pre-construction — estimating costs, preparing budgets, advising on procurement routes
- Tendering — preparing bills of quantities, evaluating contractor bids
- Construction — measuring completed work, valuing variations, managing cash flow
- Post-construction — agreeing the final account, resolving disputes over cost
Bills of Quantities: The Core Document
A Bill of Quantities (BoQ) is a document that lists, in detail, all the materials, labor, and work items needed for a construction project, along with their quantities. It’s used to get comparable, accurate tenders from contractors, since every bidder is pricing against exactly the same list of items.
A simplified example of what a BoQ line item looks like:
| Item | Description | Unit | Quantity | Rate | Total |
|---|---|---|---|---|---|
| 1 | Excavate foundation trench | m³ | 45 | $28 | $1,260 |
| 2 | Concrete foundation, grade 30 | m³ | 12 | $145 | $1,740 |
| 3 | Common brickwork, 225mm wall | m² | 210 | $62 | $13,020 |
Each row represents a “measured item” — a specific, quantifiable piece of work, priced per unit.
Methods of Measurement
Quantity surveyors don’t measure work arbitrarily — they follow standardized rules so that measurements are consistent and comparable across projects and companies. Common measurement standards include:
- NRM (New Rules of Measurement) — widely used in the UK
- SMM7 (Standard Method of Measurement, 7th edition) — an older UK standard, still referenced in some contracts
- POMI / CESMM — specialized standards for particular trades or civil engineering work
These standards define exactly how to measure and describe each type of construction work — for example, specifying whether brickwork should be measured by area (m²) net of window openings, or how excavation volume should account for working space around a foundation.
Cost Estimating vs Cost Planning
These two terms are often confused, but they serve different purposes at different project stages:
- Cost estimating — a rough calculation of likely project cost, often done very early, before detailed design exists (e.g., using a cost-per-square-meter benchmark from similar past projects)
- Cost planning — a more detailed, structured cost model built up as the design develops, broken down by building element (substructure, superstructure, finishes, services) to control cost throughout the design process
Cost planning becomes progressively more accurate as the design matures — an early “elemental cost plan” gets refined into a detailed cost plan once drawings are more developed.
Procurement Routes: How Contracts Get Awarded
Part of a quantity surveyor’s job is advising on how a project should be procured — meaning, how the contract between client and contractor is structured. Common routes include:
| Procurement route | Key feature |
|---|---|
| Traditional (lump sum) | Design completed first, then contractor prices and builds to that design |
| Design and Build | One contractor is responsible for both designing and constructing the project |
| Management contracting | A management contractor coordinates multiple trade contractors, for fee |
| Construction management | Client contracts directly with trade contractors, coordinated by a construction manager |
Each route allocates risk differently between client and contractor — a key part of a QS’s advisory role is helping a client choose the route that fits their priorities (cost certainty, speed, design control, and so on).
Variations and Valuations
During construction, changes to the original design are common — these are called variations. When a variation occurs (say, the client wants an extra room, or ground conditions turn out different from what was expected), the quantity surveyor is responsible for:
- Assessing the cost impact of the change
- Valuing the work using rates already established in the contract (where possible) or agreeing fair new rates
- Updating the overall project cost forecast accordingly
This ongoing cost tracking is often summarized in monthly interim valuations, which determine how much the contractor gets paid at each stage of construction.
The Final Account
Once construction is complete, the quantity surveyor prepares the final account — the definitive, agreed total cost of the project, reconciling the original contract sum with all variations, claims, and adjustments that occurred along the way. Getting to an agreed final account can itself be a lengthy negotiation, especially on complex projects with many variations.
Common Areas Students Find Difficult
- Confusing cost estimating with cost planning — as covered above, these serve different stages and levels of design detail
- Measurement rule inconsistency — applying general measurement logic without following the specific rules of the method being used (NRM vs SMM7, for instance) leads to incomparable figures
- Underestimating procurement route impact — students often focus purely on cost without considering how procurement route affects risk allocation and project timeline
- Treating variations as simple add-ons — a variation can affect other parts of the project too (knock-on costs, delay costs), not just the direct cost of the changed item itself
Frequently Asked Questions
Do quantity surveyors need to know how to build things? Not in a hands-on trade sense, but a strong understanding of construction methods and sequencing is essential — you can’t accurately measure or cost work you don’t understand technically.
What’s the difference between a Bill of Quantities and a cost plan? A Bill of Quantities is a detailed, itemized list used mainly for tendering and measuring actual work done. A cost plan is a budgeting tool used earlier in a project, organized by building element rather than detailed trade items.
Is quantity surveying more about construction or accounting? Both — it combines construction knowledge (to understand and measure work accurately) with financial and contractual skills (to manage budgets, valuations, and risk).
What software do quantity surveyors commonly use? Common tools include CostX, Bluebeam, and Cubit for measurement and takeoff, along with general cost management and BIM-integrated tools depending on the firm and project size.
