One of our Chelsea Mews House projects where NGA acted as the QS in addition to our role as Architect and Contract Administrator ensuring the costs remained on track and the builder was held accountable throughout the build.

In any construction project, the spotlight tends to fall on design and delivery: The architect’s vision, the builder’s craftsmanship, the transformation of a space. But behind all of this sits a vital, often invisible function: the management of costs. Someone has to keep track of what has been agreed, what has changed, and how much it all really costs. That person is the Quantity Surveyor (QS).

The role of a QS is often misunderstood, especially in private residential work where design takes centre stage. Yet when it comes to delivering a well-run project, completed on budget and without unpleasant surprises, their contribution is essential.

This article sets out the QS’s responsibilities before and during construction, how the role interacts with others on the team, and what happens when no QS is appointed.

What Is a Quantity Surveyor?

A Quantity Surveyor is the professional responsible for the commercial and financial management of a construction project. They work on behalf of the client to ensure that:

The costs of the project are understood and controlled
Payments made to the contractor reflect actual progress on-site
Variations to the design or scope are assessed and recorded accurately
The client is protected from financial risk

The QS's involvement typically begins well before construction starts and continues through to completion.

What Does a Quantity Surveyor Do Before Construction?

The QS plays a key role in setting realistic expectations early in the design process and providing the financial structure that underpins the entire project. Their pre-construction responsibilities include:

1. Preparing Cost Estimates

Based on the architect’s initial concept and outline drawings, the Quantity Surveyor prepares an estimated construction cost — a crucial early-stage figure that helps clients understand the likely financial commitment involved in bringing the proposed design to life.

This process often begins with a broad benchmark, typically using cost per square metre data derived from similar, recent projects in the area. While this offers a useful starting point, the estimate becomes increasingly refined as more information becomes available — factoring in site-specific constraints, proposed materials, structural complexity, planning policy, and the quality of finishes the client is aiming for.

As the design develops, the QS draws on up-to-date market data and pricing intelligence to create a more detailed cost breakdown, covering elements such as demolition, excavation, structural work, fit-out, joinery, services, professional fees, and VAT. This helps ensure the project brief aligns with the client’s budget — and allows for adjustments early enough to avoid costly redesigns later.

Importantly, this kind of cost advice isn’t just valuable after a property has been purchased. For many clients, commissioning a QS as part of a pre-sale feasibility study can be incredibly worthwhile. When considering a property to buy — particularly if it's a period home in need of renovation, or a site with development potential — understanding the likely build costs before making an offer can make all the difference.

In these situations, a QS-led cost appraisal based on outline architectural ideas gives clients the insight they need to:

Assess whether a potential purchase fits within their overall project budget (including works, fees, VAT, and contingencies)
Inform their offer strategy — particularly useful if negotiations are competitive
Compare multiple sites or properties with greater confidence
Avoid surprises post-purchase that might compromise their original intentions

When included as part of an architect-led feasibility package, early cost planning creates a much more holistic picture. Clients aren’t just seeing what could be designed — they’re seeing what it might realistically cost to build, and whether it’s the right investment from the outset.

2. Writing Up the Schedule of Works

An essential task for the Quantity Surveyor is preparing the Schedule of Works — a detailed, itemised Excel document that sets out all the elements of the project. This schedule is based on the architect’s full set of drawings, specifications, and construction details. It breaks the build down into logical, clearly described work packages, covering everything from demolition and structural works to internal finishes, joinery, mechanical and electrical systems, and external landscaping.

The Schedule of Works forms the foundation for pricing, tendering, and monthly valuations during construction. It ensures every component is accounted for, and that the progress of the build can be assessed in a structured and measurable way.

When the architect is also acting as the QS, there are additional efficiencies. Because the same team is handling both design and cost control, the design intent can be embedded directly into the Schedule of Works. This means the architectural drawing set doesn't need to contain every possible detail — some of that information can instead be expressed in written form within the specification or schedule. The architect has the discretion to decide the most efficient way to communicate the design — whether graphically or textually — without duplicating effort.

In contrast, when the architect and QS are separate consultants, the drawings must stand alone as the definitive description of the design. The QS will rely solely on what is shown on the drawings to produce their schedule, meaning the architectural package must be highly detailed and fully coordinated to ensure nothing is omitted or misunderstood. This means a greater number of drawings have to be produced which in turn affects the architect’s fees.

This distinction affects how design information is produced and communicated. When architect and QS are integrated, the project benefits from a more fluid and flexible process. When separate, the boundaries are clearer, but the drawing set must do much more of the heavy lifting to convey the full design vision.

3. Analysing the Returned Schedule of Works from Tendering Contractors

Once the tender package has been issued and pricing is received back from contractors, the QS undertakes a thorough analysis of each builder’s completed Schedule of Works. This document usually at least 20 pages long, contains the contractor’s breakdown of how they propose to price every element of the project, line by line.

The QS’s role at this stage is to scrutinise the returned figures in detail, looking for:

Duplicated costs — where the same item may have been priced in multiple sections or unnecessarily repeated
Missing or underpriced items — which may have been overlooked or priced very low as a way to secure the job
Unrealistic assumptions — such as contingency allowances that are too low, or excessive overheads and profit margins
Inconsistencies between contractors — where one quote differs significantly from others for the same scope of work

This analysis helps ensure that the tender return is not just within budget, but genuinely robust and deliverable. It reduces the likelihood of cost surprises later, where a contractor might attempt to recoup missed costs through variations.

Armed with this insight, the QS is also in a position to negotiate intelligently with the preferred contractor. Instead of simply asking for an overall discount, the QS can target specific areas that appear inflated or vague and suggest adjustments — aligning the cost more closely with market expectations or benchmark data.

In some cases, the QS might request a revised tender based on these discussions. In others, value engineering suggestions may be put forward, alternative materials or construction methods that can reduce costs without compromising the design intent.

This tender review phase is a critical step in securing best value for the client, and in building a transparent and constructive relationship with the chosen contractor from the outset.

4. Cash Flow Forecasting

The QS can prepare a cash flow forecast showing when the client is likely to make payments over the life of the project. This is essential for financial planning — particularly useful when clients are drawing down funds, managing multiple sources of finance, or simply want to avoid unexpected peaks in expenditure.

What Does a Quantity Surveyor Do During Construction?

Once the project is underway, the QS continues to protect the client’s financial interests through regular monitoring, assessment, and documentation. Their responsibilities during the build phase include:

1. Valuations

Each month, the contractor submits a valuation — essentially, a statement outlining what work has been completed and how much money they believe is now due. This forms the basis of the monthly payment cycle.

The Quantity Surveyor visits the site to review the progress in person, comparing what has been built against the drawings, specifications, and any instructions issued to date. They then assess whether the claimed value accurately reflects the work that has genuinely been carried out. Following this review, the QS issues a recommendation (or interim certificate) for payment — advising the contract administrator or client on how much should be released that month.

This process is essential to prevent overpayment, which can put the client at risk if funds are released for incomplete or substandard work. It ensures the contractor is paid fairly and promptly, but only for what has actually been achieved and approved.

In addition to this, most standard building contracts include a retention clause — typically withholding 5% of each payment throughout the construction phase. This retention sum serves as a financial safeguard for the client, encouraging the contractor to complete the works to a high standard and return to rectify any defects. Half of the retention is usually released upon practical completion, with the remaining half released after the defects liability period (often 6 or 12 months), once all outstanding issues have been resolved.

Together, the monthly valuation process and retention mechanism provide a robust system of financial control, ensuring that payments remain proportionate, transparent, and aligned with actual progress on site.

2. Managing Variations

Projects rarely go exactly to plan. Whether changes are requested by the client or triggered by unforeseen conditions on site, variations are a normal part of any build.

The QS takes responsibility for:

An example of one of our Variation log documents - known as a Contract Administration Instruction document - Text scrambled so that confidential information is not legible.

Reviewing the cost implications of any proposed variation
Before any changes are made on site, we assess what they mean financially — so clients can make informed decisions with clarity and confidence.
Requesting a clear cost breakdown from the contractor
We don’t accept vague or lump-sum figures. Instead, we ask for a transparent, itemised breakdown of labour, materials, and overhead — which we can then review line by line.
Advising whether the proposed cost is reasonable
With our knowledge of current market rates and typical benchmarks, we can advise clients whether a cost is fair, high, or questionable — and negotiate if needed.
Recording and tracking each approved variation against the original contract
Every agreed change is formally documented, with costs recorded and logged. This creates a clear, auditable record that avoids confusion later.
Monitoring cumulative variations against the agreed budget
We keep a running total of all variations to ensure the overall cost stays within what’s been allowed — flagging if a series of small changes begins to have a bigger impact.
Ensuring that payments reflect real progress and signed-off work
We check each monthly valuation against what’s actually been built and what has been approved — so clients are never paying ahead of progress.
Providing clients with a clear audit trail of financial decisions
Every change, every cost, and every payment is tracked and presented clearly — giving clients peace of mind and full transparency throughout the project.

3. Cost Control and Forecasting

The QS continues to monitor how each variation or site issue affects the overall project budget. They may update the original forecast at regular intervals or provide reports at key stages.

This helps the client understand how decisions made during the build impact the financial trajectory of the project — allowing for timely adjustments.

4. Final Account

At the end of the project, the Quantity Surveyor prepares the final account — a comprehensive reconciliation of all project costs from start to finish. This document goes beyond simply listing the contract sum; it captures every approved variation, provisional sum adjustment, agreed omission, and any fluctuation in scope that occurred during the build.

The process of compiling the final account involves carefully cross-checking the contractor’s claims against site progress, issued instructions, and payment certificates. The QS reviews all documentation to ensure that nothing has been missed or duplicated, and that the contractor is paid fairly — but not beyond what was agreed.

This final review is essential for transparency and accountability, providing the client with a clear and accurate financial summary of the entire project. It also serves as the formal closure of the construction contract, giving both client and contractor a clean and agreed financial endpoint, with no lingering ambiguity or unresolved claims.

By completing this process thoroughly and professionally, the QS protects the client from post-completion disputes and ensures that the financial close of the project is as well considered as the design and construction stages.

How the QS Fits Within the Project Team

The Quantity Surveyor is a central figure in the wider consultant team, working alongside:

The Architect, who is focused on delivering design quality
The Contract Administrator, who manages instructions, certificates, and compliance
The Contractor, who delivers the build on site

Unlike the architect or builder, the QS provides a purely commercially focused perspective. Their goal is not aesthetic or practical execution, but financial control — ensuring that the client pays for what’s been agreed, and no more.

This is especially valuable when assessing variation claims or challenging costs that appear inflated or unclear.

What Happens If No QS Is Appointed?

Not every private residential project includes a dedicated QS. When one is not appointed, the key responsibilities still exist — they simply fall to others or, in some cases, remain unaddressed. At NGA all of the projects that we work on will use a QS, either in house provided by us or with a separate consultant.

Two common alternatives are:

1. Client Takes On Cost Assessment

The contractor submits variation costs directly to the client, who must decide whether the costs are reasonable. The architect or contract administrator then issues the instruction based on the client’s approval.

This approach relies on the client’s own judgement and willingness to challenge or question costs — which may be uncomfortable or risky for those unfamiliar with construction pricing.

2. Prime Cost Contract (Contractor Bills for Work as Needed)

In a cost-plus model, the contractor is authorised to proceed with changes as needed, then submit receipts and apply their agreed overhead and profit margin. The client pays actual costs, with no pre-approval.

While simple to administer, this approach provides the least financial control. Without someone reviewing receipts or costs against alternatives, there's little incentive for efficiency and budgets can quickly escalate.

Why Appoint a Dedicated QS?

Bringing a professional QS on board from the beginning and retaining them throughout the project gives the client:

Understanding the cost implications of the proposed design at preliminary design stage before proceeding to the more time consuming and expensive detail design stage, so that the proposed design is realistic for the budget the client has in mind.
Confidence that payments and costs are justified
Clarity about changes and their implications
Independent advice that balances value with quality
A structured, documented relationship with the builder with regards to cost and payment due
Protection from overpayment or poor financial management

While the QS’s fee is an additional cost, their value typically outweighs this — by preventing unnecessary spend and giving the client financial peace of mind.

A Note on Professional Titles

The term “Quantity Surveyor” is not a protected title in the UK. Unlike “Architect,” which is regulated by law, any professional offering cost management services — such as valuations, variation reviews, and final account preparation — can legally describe themselves as a Quantity Surveyor.

However, the title “Chartered Quantity Surveyor” is protected and may only be used by qualified members of the Royal Institution of Chartered Surveyors (RICS).

On smaller residential projects, it's common for experienced architects or project managers to take on QS responsibilities, provided the scope is clearly defined and the individual is competent and insured for the role. As with any consultant appointment, the key is transparency — about responsibilities, qualifications, and where the limits of the role lie.

Our Services

NGA can provide QS services in-house

At Nancy Gouldstone Architects, we recognise how important cost control is to the success of a high-end residential project. We on occasion work with excellent independent quantity surveyors and are always happy to collaborate as part of a wider professional team.

However, with over 12 years of experience undertaking Quantity Surveying services, we can also offer this role in-house, delivering Quantity Surveyor services alongside our architecture and contract administration work. This gives clients the benefit of a streamlined, fully coordinated service — often particularly effective on smaller or fast-moving projects.

We advise on a case-by-case basis when this approach is appropriate, and always ensure that the chosen structure supports the specific needs of the project, the client, and the team.

Why We Love Offering QS Services

There’s something deeply satisfying about understanding how a design lives and breathes not just in concept, but in cost. We take real pleasure in working through the numbers. We love Excel (truly) and the clarity it brings when translating our designs into the financial structure of a project.

Carrying out quantity surveying in-house gives us a tighter grip on quality. When we control valuations and variations, the contractor understands that we’re not just the creative lead, we hold the financial reins too. This naturally builds respect and helps maintain the standards we care so much about.

But more than that, it puts us right in the client’s shoes. We are constantly alive to the reality of cost, how even the smallest decision can shape the overall investment. That means we can design beautifully and confidently, with an instinctive sense of how to balance value and luxury. Over time, we’ve developed a deep understanding of what costs more, what’s worth it, and where to make smart savings without compromising the feel or finish.

In short, we design better when we know the numbers. And we believe our clients get better buildings as a result. If you are considering purchasing a new property and would like some initial advice, we would be pleased to speak with you. Please book a consultation using the button below.

Book a consultation

Who Manages the Money? The Role of the Quantity Surveyor in Residential Projects

What Is a Quantity Surveyor?