Quantity surveying (QS) is the discipline that manages the financial and contractual aspects of a construction project — from early cost planning through procurement and contract administration to final account. A quantity surveyor’s work starts with the drawings and specifications and translates them into numbers: how much material, how much labour, how much it will cost, and what the contract should say about who is responsible for what.

What a QS Does Across the Project Stages

At the feasibility stage, a QS produces an order-of-magnitude cost estimate based on the building type, size, and location — typically using published cost-per-square-metre rates from current market data. This tells the client whether the project is financially viable before significant design fees are committed.

At design development, cost plans are progressively refined as the design becomes more detailed. Each cost plan identifies the cost of each building element (substructure, frame, upper floors, roof, external walls, internal finishes, M&E services) and tracks whether the project is within budget as design decisions are made.

At procurement, the QS prepares the bill of quantities (BQ) — a detailed schedule of every item of work, measured from the drawings and described per the standard method of measurement (SMM7 in the UK, IS 1200 in India). Contractors price each item to produce their tender submission. The BQ creates a common basis for comparing tenders and forms part of the contract.

During construction, the QS values monthly progress payments, assesses and agrees variations (changes to the scope), and manages the contract programme. At completion, the QS prepares the final account — the agreed final sum taking into account all variations, claims, and price adjustments.

Taking Off Quantities from Drawings

Taking off (measuring quantities from drawings) follows strict rules. Concrete is measured in cubic metres; reinforcement in tonnes (calculated from the bar bending schedule); formwork in square metres of contact area; brickwork in square metres; structural steelwork in tonnes; painting and floor finishes in square metres. Dimensions are always taken in the order: length, width, height (or depth).

Quantities are measured net (the theoretical quantity in place, with no allowance for waste) — waste factors are for the contractor to assess and allow for in their rates. The standard method of measurement defines precisely how each item is measured, what is included in the item description, and what is measured separately.

Cost per Square Metre Rates

Cost-per-GFA (gross floor area) rates are the fastest tool for early feasibility. Current rates vary widely by building type, specification, and location, but indicative ranges (UK, 2024-2025 basis): residential apartments £2,000–3,500/m², commercial offices £2,500–4,500/m², hospitals £4,000–8,000/m², industrial sheds £500–900/m². These are construction costs only — professional fees, land, finance costs, and VAT are additional.

Estimating and Cost Control Software

QS practitioners use specialist software for taking off and cost planning: CostX (on-screen takeoff from PDF drawings), Causeway, Procore (cost management), and Cubit are widely used. BIM models allow quantities to be extracted directly from Revit schedules and imported into cost management platforms, reducing manual takeoff time for straightforward items while leaving the QS to focus on complex or unique elements.

The Relationship Between QS and the Drawing Set

A quantity surveyor reads drawings differently from a contractor or designer. Their focus is on completeness (can every element be measured?), consistency (do the drawings agree with the specification?), and buildability (is the sequence of construction logical?). Discrepancies between drawings — a wall shown on the architectural plan but missing from the structural drawing, or a ceiling finish specified in the room schedule but not shown on the reflected ceiling plan — create pricing ambiguity that inflates tender prices or generates disputes during construction.

Conclusion

Quantity surveying sits at the intersection of design, construction, and finance. It is the discipline that keeps projects honest — translating design ambitions into realistic costs before commitments are made and tracking value through every decision during construction. For anyone producing drawings, understanding how a QS reads and measures from them is a valuable perspective that improves drawing completeness and reduces tender queries.