What Does a Quantity Surveyor Do? A South African Guide

On a building project, the quantity surveyor is the person who keeps the money honest. The architect designs the building. The engineer makes sure it stands up. The contractor builds it. The quantity surveyor (QS) measures it, prices it and controls its cost, from the first rough estimate to the final account. When the role is done well, you keep your margin. When it is left to chance, cost overruns arrive as a surprise.

This guide explains what a quantity surveyor does day to day, where they sit on a project, how a monthly valuation works, how the role differs from an estimator or an architect, and how to tell when you need one. It is written for developers, contractors and clients who keep hearing “ask the QS” and want to know what that means.

What a Quantity Surveyor Does

A quantity surveyor runs the cost and commercial side of a project across its whole life. In practice, the work comes down to a set of jobs that repeat on every project:

Estimating and feasibility. Give an early, defensible number for what the project will cost, before anyone commits.
Bills of quantities (BOQ). Measure the works from the drawings and turn them into an itemised bill that contractors price for the tender.
Procurement and contracts. Advise on the contract form, compare tenders and price the risks.
Measurement and valuation. Measure the work done on site and value it for the monthly payment.
Variations and claims. Price changes and assess claims, so the commercial position stays fair.
Cost control and reporting. Track committed and actual cost against budget, and forecast the final cost.
Final account. Agree the final value of the contract once the work is finished.

Put simply, the QS is the person a director calls to ask, “Are we still going to make our margin?”

Where the QS Sits: Contractor, Consultant or Developer

One job title covers three different seats, so it matters which one you mean. They share the same skills but work for different people.

The seat	Who they serve	What they focus on
Contractor’s QS	The building contractor	Getting paid: pricing tenders, measuring work, submitting payment claims with solid backup
Professional QS (PQS)	The client or developer	Independent cost advice: feasibility, BOQ, fair valuations, contract administration, reports to the funder
Developer’s in-house QS	The development business	The cash position: cost to complete per unit, budget versus actual, feasibility across projects

Most projects have two QSs facing each other every month. The contractor’s QS presents what has been built. The client’s PQS checks it and recommends what should be paid. That tension is useful. It keeps the numbers straight on both sides.

The QS Across a Project

The easiest way to understand the role is to follow the money from idea to handover. The QS has a task at every stage:

Feasibility. Before land is bought, the QS gives an early cost estimate so the developer can test whether the numbers work.
Design and BOQ. As the drawings develop, the QS measures the works and writes the bill of quantities.
Tender and award. The QS compares tenders on a like-for-like basis and advises on the contract form, such as JBCC, NEC or GCC.
Construction. Each month, the QS measures completed work, prices variations and prepares the payment valuation. The contract decides how much retention is held back.
Cost control. Throughout the build, the QS tracks cost against budget and forecasts the cost to complete. An overrun shows up as an early warning, not a shock at the end. Our guide on preventing construction cost overruns covers the usual causes.
Final account. When the work is done, the QS agrees the final contract value with the other party.

A quick test. If you cannot answer “What has this cost so far, what is left to spend, and are we still on margin?” in any given week, you have the gap a quantity surveyor fills.

How a Monthly Valuation Works

The monthly valuation is where the QS turns site progress into a payment amount. Here is a simplified example for a housing project with 10% retention and VAT at 15%:

Line	Amount
Work completed to date (measured on site)	R4,200,000
Materials on site	R150,000
Gross value to date	R4,350,000
Less retention (10%)	R435,000
Net value to date	R3,915,000
Less amounts certified before	R2,970,000
Amount due this month (excl. VAT)	R945,000
VAT at 15%	R141,750
Total due this month	R1,086,750

Each line needs evidence. The QS keeps measurements, site photos, approved variations and delivery notes behind the numbers. Without that backup, the other side will cut the claim. The retention percentage and release dates come from the contract, so always check the contract data rather than assuming a figure. Our guide to progress payment certificates in South Africa explains the full certificate cycle.

QS, Estimator or Architect: Who Does What

These three roles are often confused, so here is the plain version. An estimator prices work, often for a contractor, to win the tender. A quantity surveyor does that too. Then the QS carries the cost through the whole build: measurement, variations, valuations and the final account. An architect designs the building. On many JBCC projects, the architect also acts as the principal agent who administers the contract. The principal agent can also be a QS or a project manager.

Role	Main job	When they are most active
Estimator	Price the work to win the tender	Before the contract is signed
Quantity surveyor	Control cost from estimate to final account	From feasibility to final account
Architect	Design the building and often administer the contract	From concept to completion

The architect owns the design. The estimator owns the tender price. The QS owns the money from start to finish.

The South African Context

Quantity surveying in South Africa follows local contracts, standards and rules. A good SA quantity surveyor knows:

Contract forms. JBCC is common for building work. NEC and GCC are common for civil and infrastructure work. Each has its own rules for valuations, retention and variations. Our guide comparing JBCC, NEC and GCC contracts sets out the differences.
Measurement standards. Building bills are usually prepared to the ASAQS Standard System of Measuring Building Work, so a quantity means the same thing to every tenderer.
The professional body. The Quantity Surveying Profession Act 49 of 2000 set up the South African Council for the Quantity Surveying Profession (SACQSP), which registers quantity surveyors. The Association of South African Quantity Surveyors (ASAQS) is the voluntary professional association.
The wider rules. CIDB grading applies to public sector work. NHBRC rules apply to new homes. VAT and retention also affect the numbers the QS controls.

This is why a cost professional trained elsewhere needs time to learn the local contracts and standards before taking on a South African project.

How to Know You Need One

What decides whether you need a QS is not project size. It is how many moving parts your money has. You almost certainly need one when:

You borrow against the project, and the funder wants independent cost sign-off before it releases drawdowns.
Client or design changes are frequent, and you are not sure every one is priced, approved and recovered.
You run more than one project and cannot compare cost across them on the same basis.
Your certified amounts keep falling below your estimate, and you cannot say why.

On a small private job with a fixed price and few changes, a contractor may manage cost without a full-time QS. Even then, many use a QS for the BOQ and the final account.

Working Well With Your Quantity Surveyor

A QS is only as good as the information they receive. Developers and contractors can make the role far more effective with a few habits:

Bring the QS in early. Cost advice at feasibility saves more money than cost control during the build.
Approve changes in writing. A variation with no written instruction is hard to price and harder to recover.
Share site records every week. The QS needs the diary, progress photos and delivery notes to value work fairly.
Agree one cost report format. Use the same layout every month, so trends are easy to spot.
Keep one source of truth. Budgets, variations and valuations should live in one system, not in five spreadsheets.

Many QS teams now use software to keep the BOQ, variations, valuations and cost to complete in one record. South African tools such as Wakha support JBCC, NEC and GCC payment certificates and budget versus actual in Rands. The software supports the QS. It does not replace their judgement. For the tooling detail, see our guide to quantity surveying software in South Africa.

The Bottom Line

A quantity surveyor keeps a project’s money honest, from the first feasibility estimate, through every monthly valuation and change, to the final account. On South African projects, with JBCC, NEC and GCC contracts, CIDB and NHBRC rules and tight funder margins, that role protects the margin you planned. The questions a QS answers never change: what has this cost, what is left, and are we still on plan?

Frequently Asked Questions

What is a quantity surveyor?

A quantity surveyor is the construction professional who manages a project’s cost from start to finish. They estimate the cost, prepare the bill of quantities, value work for payment, price changes and agree the final account. In South Africa, professional quantity surveyors register with the SACQSP.

Is a quantity surveyor the same as an estimator?

No, but the roles overlap. An estimator prices work to win a tender. A quantity surveyor also does that, then carries the cost through the whole build: measurement, variations, valuations and the final account. Every QS can estimate. Not every estimator does the full QS job.

Do I need a quantity surveyor for a small project?

If you borrow against the project, have frequent changes or need certified monthly valuations, the answer is usually yes. The trigger is how complex the money is, not the floor area. Even one house with monthly payments and changes can lose margin without proper cost control.

What qualifications does a QS have in South Africa?

Most South African quantity surveyors hold an accredited degree in quantity surveying. To practise as a professional, they register with the South African Council for the Quantity Surveying Profession (SACQSP). Many are also members of the ASAQS.

What is the difference between a contractor’s QS and a client’s QS?

The contractor’s QS works to recover the contractor’s cost and get paid. The client’s professional QS (PQS) gives independent advice and recommends fair value for the client. On most projects both are involved, and the tension between them keeps the valuation honest.

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