How do you approach producing a cost estimate at early feasibility stage?

At feasibility stage the information is always incomplete, so I am transparent with the client about the assumptions underlying the estimate and the contingency applied to reflect that uncertainty. My starting point is elemental cost planning based on known floor areas and building type, using published cost data such as BCIS as a benchmark, adjusted for location factor, procurement route, and site conditions. I break the estimate into clear elements: substructure, frame, envelope, internal finishes, mechanical and electrical, and external works, because that structure makes it easier to track cost movement as the design develops. I apply a design development allowance at RIBA Stage 2, typically 10 to 15%, and a separate construction contingency. I am explicit about what is excluded: planning fees, professional fees, VAT, and abnormals. A cost plan that hides uncertainty in rounded numbers creates problems later when the client thinks they had a fixed figure.

What is the difference between a JCT and an NEC contract, and when would you use each?

JCT contracts are generally considered more contractor-friendly and are widely used in building work, particularly in the private sector. They tend to be more prescriptive and rely on traditional roles for the architect and contract administrator. NEC contracts are designed around collaborative working and early warning mechanisms. The NEC3 and NEC4 suite use plain language, require both parties to act in a spirit of mutual trust, and place a strong emphasis on proactive programme management through the early warning register and compensation event process. I would tend to recommend JCT for straightforward, well-defined building projects where the client has an experienced contract administrator. I would lean toward NEC for complex, long-duration infrastructure or fit-out projects where early identification of programme risk matters as much as cost control. The procurement route also influences the choice: design and build suits JCT DB; target cost contracts suit NEC Option C.

How do you manage subcontractor procurement on a design and build project?

On a design and build project, my first step is producing a detailed procurement schedule aligned to the programme, identifying long-lead items and the dates by which each package needs to be let to avoid delaying the works. I prepare tender documents for each package: scope of works, employer's requirements, preliminaries, and pricing document. I manage a competitive tender process with a minimum of three tenderers per package, assess returns on a like-for-like basis using a tender analysis, and present a recommendation to the client or contractor with a clear basis of award. For specialist packages I often carry out a mid-tender query session to resolve ambiguities before returns come in, which reduces the risk of qualifications in the submissions. Post-award, I set up a structured scope review process at each design stage to check that subcontractor packages still align with the current design, because scope gaps on D&B are the most common source of disputes.

How do you handle a contractor who is consistently submitting inflated applications for payment?

I deal with inflated applications through rigorous assessment rather than confrontation. My payment assessment is always evidence-based: I compare the application against the contract programme, the agreed activity schedule or bill of quantities, and any substantiation the contractor has provided. Where items are assessed at a lower value than claimed, I document my reasoning clearly in the payment notice so the contractor has a transparent basis to challenge if they disagree. I also have a direct commercial conversation with the contractor's QS early in the project to align on the assessment process, so there are fewer surprises at payment stage. If a pattern of inflation persists, I escalate to a commercial meeting with the contractor's commercial director and document the agreed position. Disputes that reach adjudication are expensive and damaging to the project programme, so early resolution is always preferable.

Tell me about a time you identified a significant cost overrun risk and what you did about it.

On a £12m commercial fit-out I was reviewing the contractor's programme in month three and noticed that the mechanical and electrical package was running four weeks behind the baseline programme, with the contractor attributing it to late design information. I ran a cost impact analysis and calculated that if the delay continued at the same rate, prolongation costs would add approximately £180,000 to the final account. I called an early warning meeting under the NEC contract, bringing together the client, contractor, and the M&E designer. We agreed a recovery programme that included additional design resource and a revised sequencing of the installation works. The delay was contained to two weeks in total, reducing the prolongation cost to around £60,000. The key was acting on the data six weeks before the delay would have become unrecoverable, not waiting for the contractor to raise it.

Describe a situation where you had to negotiate a final account with a difficult contractor.

On a public sector refurbishment project, the contractor submitted a final account that was £340,000 above the contract sum, predominantly made up of compensation events and loss and expense claims for disruption. I carried out a detailed review of each claim against the contract records: site instructions, early warning notices, contractor's notices, and programme comparison between baseline and as-built. I found that approximately £180,000 of the claims lacked the contractual notice required under the JCT conditions, and a further £90,000 related to events that were clearly contractor-risk items under the contract. I presented my assessment with a clear audit trail at a commercial meeting. After two rounds of negotiation, the final account settled at £68,000 above the contract sum. The lesson was that disciplined record-keeping throughout the project is the single most important factor in final account resolution.

Give an example of a time you had to advise a client to spend more money than they wanted to.

A developer client wanted to reduce the specification on the building envelope to cut costs by £250,000 on a residential scheme. The proposal was to reduce the cladding U-value from 0.18 to 0.28 W/m²K, which would have met minimum Building Regulations but fallen short of the EPC Band B target in the planning consent. I modelled the financial impact: the immediate saving of £250,000 was offset by an estimated £80,000 to £110,000 reduction in sale values across the units, plus the risk that the development would not comply with planning and require a retrospective application costing time and fees. I presented this as a net cost rather than a saving. The client agreed to retain the original specification for the two street-facing blocks and accept a reduced spec on the rear block only, which gave them a cost reduction of £95,000 while protecting the planning compliance and headline sale values.

How do you value a variation under a JCT Design and Build contract?

Under JCT Design and Build, variations are instructions issued by the employer to change the employer's requirements. The valuation rules are set out in Section 5 of the contract. Where the work is of a similar character to work already in the contract bills or activity schedule and executed under similar conditions, it is valued at bill rates. Where conditions differ substantially, rates are adjusted pro rata. Work that cannot reasonably be valued by reference to bill rates is valued at fair rates and prices, which in practice means a cost-plus approach with reasonable contractor margin. I always try to agree the value of a variation before the work is instructed if possible, issuing a change request and asking the contractor for a quotation to review. Pre-agreed variations reduce disputes on final account significantly. For variations that cannot be pre-agreed, I require the contractor to keep detailed records of labour hours, plant, and materials, and I validate those records against my own site observations.

Walk me through how you would prepare a cost plan for a new office building.

I structure a cost plan at RIBA Stage 3 around the BCIS elemental structure: preliminaries, substructure, frame, upper floors, roof, external walls, windows, internal walls, internal doors, wall finishes, floor finishes, ceiling finishes, fittings, sanitary, mechanical services, electrical services, lifts, and external works. I populate each element using a combination of benchmarked rates per square metre and measured quantities where the design is developed enough to measure. For mechanical and electrical I work closely with the M&E engineer to get early budget confirmation of the services strategy, because M&E typically represents 20 to 30% of a commercial office cost plan and is the element with the highest variability. I hold contingency centrally in the cost plan rather than embedding it in individual elements, because embedded contingency is invisible to the client and creates a false sense of certainty. I present the cost plan with a clear statement of assumptions, exclusions, and the confidence level of each element.

How do you assess and certify a contractor's interim application for payment?

My assessment process follows the contract: I have a fixed period from the due date to issue a payment notice under the Housing Grants Act, and missing that date means the contractor's application becomes the payable amount by default. I start by checking the application against the activity schedule or contract sum analysis, verifying the percentage complete claimed for each work section against my own site visit records. I deduct any retention at the contractual rate, any previous overpayments, and any sums in dispute that have been formally contested. For variations, I include only those that have been instructed in writing and valued. I produce a detailed payment assessment that shows my calculation transparently, not just the net figure. I issue the payment notice before the final date for payment and, where I am withholding any sum, issue a pay less notice within the required period with specific reasons for each deduction. Procedural compliance on payment is not optional: it is the foundation of the commercial relationship.

Quantity Surveyor Interview Questions

Quantity Surveyor

Quantity surveyor interviews test your ability to control costs, manage contracts, and keep projects financially on track from feasibility through to final account. Interviewers want to see technical knowledge of standard forms of contract, practical experience of change management, and sound commercial judgment. This guide covers the questions most likely to come up and the answers that demonstrate you can protect a client's budget without damaging contractor relationships.

Common Quantity Surveyor Interview Questions

What Hiring Managers Look for in Quantity Surveyor Interviews

What hiring managers really look for in Quantity Surveyor candidates:

Contract literacy. You should be able to discuss JCT and NEC contract mechanisms in detail, not just name them. Interviewers will probe your knowledge of valuation rules, payment notices, and compensation events.
Commercial judgment. Strong QS candidates understand that cost control is not about being the cheapest: it is about protecting the client's financial position across the whole project lifecycle.
Record-keeping discipline. The ability to resolve final accounts and defend payment assessments depends on having contemporaneous records. Show that you treat documentation as a professional obligation, not an afterthought.
Stakeholder management. QS work involves managing difficult conversations with contractors, clients, and project teams. Give examples that show you can hold a commercial position under pressure while maintaining working relationships.
Proactive risk identification. Hiring managers want QS professionals who raise cost and programme risks early, not those who report overruns after they have happened.

Questions to Ask Your Interviewer

→What contract forms does the practice use most frequently and are there standard templates in place?

→How is the QS team structured across projects and what level of autonomy do surveyors typically have on cost management decisions?

→What software does the team use for cost planning, estimating, and contract administration?

→How does the practice handle disputes with contractors when they arise and what support is available?

→What does the CPD programme look like and is there support for RICS APC if I am not yet chartered?

Quantity Surveyor

Common Quantity Surveyor Interview Questions

Behavioural Interview Questions for Quantity Surveyor Roles

Technical Questions for Quantity Surveyor Candidates

What Hiring Managers Look for in Quantity Surveyor Interviews

Questions to Ask Your Interviewer

Practise These Questions Before Your Interview

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