What Is a Quantity Surveyor — and Do You Need One for Your Project?
A quantity surveyor (QS) is a construction cost and contract professional — sometimes described as the "financial manager" of a building project. They manage the commercial side of construction: estimating costs, preparing bills of quantities, administering contracts, valuing works in progress, managing variations, and agreeing final accounts. Here's what they do, when you need one on a domestic project, and what value they add.
What a QS Does
Cost planning and estimating. At the design stage, the QS produces estimates of likely project cost based on the design information available. These estimates are updated as the design develops — giving the client regular, reliable cost intelligence throughout the pre-construction period.
Procurement and tendering. The QS prepares tender documents (bills of quantities or schedules of works) that allow contractors to price the project on a consistent basis, and manages the tendering and contractor selection process.
Contract administration. During construction, the QS values the works in progress (for monthly payment certificates), agrees variations and their cost, manages claims, and prepares the final account at project completion.
Post-contract cost control. The QS tracks expenditure against the budget throughout the project, flagging overspend risks and helping the client make informed decisions about scope changes.
When You Need a QS on a Domestic Project
For smaller domestic projects (under £100,000), a QS is not typically employed separately — the contractor's estimate and a simple written contract usually suffice, with the client managing cost control directly. However, where cost certainty is important — particularly on larger or more complex projects — a QS adds genuine value:
Projects above £150,000–£200,000. At this scale, the QS's fee (typically 2–4% of project cost) is usually recovered in cost savings, better procurement, and more reliable cost control.
Projects with significant uncertainty. Where the scope is not fully defined, where conditions are unpredictable, or where the client has a tight budget that requires active management, QS involvement provides a discipline that prevents cost overrun.
Contentious projects or contract disputes. Where a contractor relationship has broken down or where a final account is disputed, an independent QS can assess the contractor's final account claim and provide an objective view of fair value.
QS Thinking in a Design-and-Build Context
RCB operates with a QS mindset throughout the pre-construction and delivery process. Our estimates are based on quantity takeoffs and current market rates, not rule-of-thumb guesses. We provide transparent cost breakdowns and manage variations through a structured process. This isn't a formal QS appointment — but it reflects the same commercial discipline.
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