The quantity surveyor turns a project into figures: they read the drawings, quantify each element of work — cubic metres of excavation, square metres of wall, kilograms of steel, numbers of doors —, apply prices, and produce the document that will allow a decision to be taken, contractors to be compared, the site to be followed and accounts to be settled at the end. They work for clients who want to know how much, for contractors who want to answer a tender, for architects who want to check that the design fits the budget, sometimes for a court that wants to know what was really done. Their work has an order — from documents to quantities, from quantities to prices, from prices to the site — and it is the only one that makes it intelligible.
From documents to quantities: taking off
Everything starts with what the surveyor receives: drawings, sections, details, specification, calculation notes, soil report. The more complete these documents, the more accurate the take-off; the more summary they are, the more assumptions the surveyor must make — and write down. The take-off breaks the work down into items, element by element, in a logical construction order, and measures each item with a method that can be checked: where each quantity comes from, on which drawing, at what scale, by what calculation. A take-off that cannot be checked is an opinion with numbers.
The surveyor also flags what the documents do not say: a connection missing from the drawings, a foundation whose depth depends on an unstudied soil, a finish not described. These silences become assumptions or provisional sums, never omissions.
From quantities to prices: estimating
To each quantity, the surveyor applies a unit price. Where does that price come from? From consultations with suppliers and contractors, from prices observed on recent comparable sites, from price databases where they exist, from the client when they impose negotiated prices. The surveyor says which was used, on what date, and for what place: the price of cement, sand, labour and transport varies from one city to another and from one quarter to the next, and an estimate without a date or a place is worth nothing. They add site overheads, general overheads, the margin when working for a contractor, taxes, and a contingency whose rate they justify rather than round off.
They do not present a price “per built square metre” as a universal truth: it is a first-approach order of magnitude, replaced by the take-off as soon as the drawings allow.
The estimate and the bill: what the client reads
The deliverable is a bill of quantities and estimate or a schedule of rates, organised by trade and by item, with quantities, units, unit prices, amounts, and — this is what distinguishes a serious practice — the list of assumptions and exclusions: what was assumed, what is not included, what depends on missing information. RICS, the professional body for property and construction, bases its standards on the ethics, conduct and competence of its members; at the scale of an estimate, ethics consists of not hiding an assumption inside a total.
The estimate says what it is for: deciding on a project, launching a tender, contracting. It is not the same document in the three cases, and the surveyor says so.
Who the surveyor counts for: three clients, three estimates
The same work is not priced the same way depending on who commissions the estimate. For the client — a private individual, a developer, an administration —, the surveyor estimates what the project should cost and prepares the document that will be used to consult contractors; they work on the side of the one who pays. For the contractor answering a tender, they calculate a cost price — materials, labour, plant, overheads — and leave management to decide the margin; they work on the side of the one who executes. For the architect or the engineer, they check that the designed project fits within the announced budget, and flag early what exceeds it. A practice may serve all three, but never on the same site: counting for the client and for the contractor at the same time is a conflict of interest, and the surveyor says so from the first conversation.
Comparing bids: reading what others counted
When the client consults several contractors, the surveyor compares their bids item by item — not only their totals. A low bid that forgot an item, underestimated a quantity or excluded an element of work is not the cheapest: it is the most dangerous. The surveyor spots the gaps, asks for explanations, and hands the client an analysis that says what each bid really contains. FIDIC’s standard contracts, widely used in international construction, rely on that clarity of quantities and prices to allocate risks between the parties.
During the site: valuations, variations, claims
The take-off does not end at signature. During the works, the surveyor checks the contractor’s monthly valuations — what has actually been executed, measured on site, against what is invoiced —, prices the changes requested by the client or imposed by the ground as written variations before execution, and tracks the gap between planned and actual. At the end, they prepare or check the final account. A site followed by a quantity surveyor ends with accounts both parties understand; a site without one often ends before a third party. The surveyor keeps a quantities log there: what was measured, when, with whom, and what was disputed — because a quantity argued over three months later, once the wall is rendered, can no longer be measured.
The limits of the surveyor’s guarantee
They guarantee the consistency of their take-off with the documents received, the calculation method, the traceability of prices and the explicit statement of assumptions. They do not guarantee the final cost of a site whose drawings change, whose ground holds surprises or whose material prices soar between estimate and purchase; they guarantee that these risks are named in their document. Nor do they replace the engineer who sizes, the architect who designs or the contractor who executes: a surveyor’s estimate on an unstudied structure is an estimate on an assumption, and they say so.
The site, safety, hidden quantities
A surveyor goes to the site: to measure the existing before works, to check a valuation, to record an unforeseen event. There they respect the site rules — helmet, footwear, escort — which the ILO code of practice on safety in construction recalls for anyone present, even for a one-hour survey. And they know that some quantities cannot be seen on the drawings: scaffolding, collective protection, site facilities, cleaning, waste removal. An estimate that forgets them forces the contractor to take them out of safety or quality.
In the African context
On the continent, the quantity surveyor often works with incomplete drawings, no specification, no soil survey, for clients who want a figure before they have a project. Their first skill then becomes that of assumptions: saying clearly what the estimate rests on, what is missing, and by how much the figure may move when the information arrives. The “per square metre” estimate circulates everywhere; the practice that explains why it is not enough, and that offers a take-off as soon as drawings exist, renders a service the client understands at the first site that goes off the rails.
Price volatility is the second variable: cement, steel, fuel and transport see rapid variations, sometimes from one month to the next, with imports, exchange rates and taxes. A dated estimate, with a validity period and an explained revision clause, protects both parties; an undated estimate becomes, within months, a source of conflict. The surveyor who follows the prices of their region — and keeps a register of them — is the one whose estimates remain useful.
The profession itself, moreover, is unevenly recognised: taught in some engineering and technical schools, absent from other curricula, without a professional body in many countries. RICS and other professional bodies offer standards that practitioners on the continent adopt; the practice that displays its method, its price sources and its assumptions builds a credibility the market does not yet guarantee through a title.
The estimate that explains its assumptions
A client who receives an estimate should be able to read, before the total: the documents it rests on and their date; the take-off method; the origin and date of the prices; the assumptions made where the documents are silent; what is excluded; the contingency and why; the validity period and the revision rule.
The total is only the last line. It is everything before it that says whether it can be trusted — and that, exactly, is what a quantity surveying and estimating practice sells.