A quantity surveyor (QS) manages the cost of a construction project from the first sketch to the final account. Engineers make sure a building stands up, and architects make sure it works and looks right. The QS makes sure it can be built for the money available, and that everyone is paid fairly for what they actually did.
This article combines our earlier guides on what a quantity surveyor does and on QS duties in Australia. It sets out the role stage by stage, with notes on how it works in Western Australia.
What does a quantity surveyor do?
In short, a QS measures, prices, forecasts and controls construction cost. That covers:
- early cost advice and feasibility budgets;
- cost plans as the design develops;
- quantity take-offs and bills of quantities;
- tender documents, tender analysis and recommendations;
- progress claim assessments and payment recommendations;
- variation and claim valuations;
- cost reports, forecasts and the final account.
QS duties at each stage of a project
1. Feasibility and early cost advice
Before land is bought or a design is fixed, a QS gives an order-of-cost estimate based on floor area, building type and site conditions. In Perth that means allowing for things like double-brick versus framed construction, site classification and earthworks on sand or clay, and current trade availability. See our early cost advice and feasibility service.
2. Cost planning
As the design develops, the QS prepares elemental cost plans (substructure, frame, envelope, finishes, services and so on) and tracks the design against budget. When the design drifts over budget, the QS offers alternatives through value engineering.
3. Measurement and bills of quantities
The QS measures quantities from the drawings to a recognised method of measurement and writes them up as a bill of quantities or trade take-off. This gives every tenderer the same quantities to price. Read methods of measurement in quantity surveying.
4. Procurement and tendering
- Advising on the procurement route and contract form (AS 4000, AS 4902, AS 4905, or housing contracts).
- Preparing pricing schedules and tender documents.
- Comparing tenders like for like, checking arithmetic and qualifications, and recommending a tenderer.
- Preparing a pre-tender estimate so the bids can be judged against an independent benchmark.
5. Construction phase (post-contract)
- Assessing monthly progress claims against the work done on site.
- Valuing variations and assessing EOT-related costs.
- Monthly cost reports with forecast final cost and contingency tracking.
- Advising on payment timeframes under the WA Building and Construction Industry (Security of Payment) Act 2021.
For more detail, see pre-contract and post-contract quantity surveying.
6. Completion and final account
The QS agrees the final account, which brings together the contract sum, variations, provisional sum adjustments and claims. The QS may also support defects, retention release and any dispute process. Read how quantity surveyors manage final accounts.
Client-side vs contractor-side quantity surveyors
| Client-side (consultant) QS | Contractor-side QS | |
|---|---|---|
| Works for | Owners, developers, government, financiers | Builders, civil contractors and subcontractors |
| Main focus | Budget, cost plans, tender analysis, claim assessment | Estimating, buying, claims, variations, margin |
| Typical outputs | Cost plans, cost reports, payment recommendations | Tender estimates, progress claims, variation submissions |
Key skills of a quantity surveyor
- Accurate measurement from drawings and models, using tools such as Bluebeam Revu and Kubla Cubed.
- Construction technology: knowing how things are built, so nothing is missed.
- Cost knowledge: current labour, plant and material rates for the local market.
- Contract knowledge: Australian Standard contracts and WA legislation.
- Communication and negotiation with designers, builders and clients.
See also the top 10 qualities of an effective quantity surveyor.
Qualifications and professional bodies in Australia
Most quantity surveyors hold a degree in quantity surveying, construction economics or construction management. Many go on to membership of the Australian Institute of Quantity Surveyors (AIQS) or the Royal Institution of Chartered Surveyors (RICS). Membership shows the QS works to recognised professional and ethical standards. Measure Manage is RICS & AIQS Accredited. If you are thinking about the career, read how to become a quantity surveyor.
Quantity surveyor vs estimator
An estimator prices work to win it. A QS manages cost across the whole project. The roles overlap, especially on the contractor side. We explain the differences in quantity surveying vs estimation.
When should you engage a quantity surveyor?
- Before buying land or committing to a design, to test feasibility.
- During design, to keep the design on budget.
- Before tender, to prepare quantities and a benchmark estimate.
- During construction, to check claims and value variations.
- When something goes wrong: disputed variations, delays or an unresolved final account.
Frequently asked questions
Do I need a quantity surveyor for a house?
Not always. For custom homes, large renovations, multi-residential projects or owner-builder projects, an independent take-off and cost check often pays for itself in avoided overruns and well-checked progress claims.
What is the difference between a QS and a building surveyor?
In WA, a building surveyor checks that the design meets the building codes and issues the Certificate of Design Compliance used for a building permit. A quantity surveyor deals with cost, quantities and contracts.
How are QS fees charged?
Usually as a fixed fee for a defined scope, such as a cost plan or BoQ, or at hourly or monthly rates for ongoing post-contract services. Ask for a fee proposal based on your drawings.
Need a quantity surveyor in Perth or regional WA? Call Measure Manage on 0498 202 445 or see our quantity surveying services.