A quotation is the output of a process, not a guess dressed up in a letterhead. Someone has taken the drawings and specification, measured or estimated quantities, priced labour and materials against those quantities, and added the costs of running a site safely and cleanly.
Understanding that sequence explains why two builders pricing the identical job can land on very different totals, and why the cheapest figure is not automatically the most complete one.
Taking off quantities
The first stage is a take-off: converting drawings and a written specification into measured quantities — square metres of plasterboard, linear metres of skirting, cubic metres of concrete, numbers of doors and sockets. Where drawings are vague, the estimator has to make an assumption, and a careful one will flag that assumption in the quote rather than bury it.
A take-off done properly takes real time, which is one reason a detailed quote for a substantial job rarely arrives within a day of the site visit. A same-day figure for a full renovation is more likely to be a rough allowance than a costed take-off.
Pricing labour by trade and duration
Once quantities exist, each trade's labour is priced against how long that quantity of work actually takes a competent operative — a bricklayer's output per day, a plasterer's coverage rate, an electrician's time per circuit. This is where experience on similar buildings matters, because output rates on an awkward period cottage are nothing like output rates on a straightforward new-build shell.
Subcontracted trades are priced by getting their own quotes against the same specification, so the main contractor's figure is really an assembly of several specialist prices rather than one person's estimate of everything.
Preliminaries: the costs of running the site
Preliminaries cover everything that supports the work without being part of the finished building: scaffolding, skips and waste removal, welfare facilities, protection of existing finishes, site insurance, supervision time and cleaning. These are real costs that scale with the length and complexity of the job.
A quote that has stripped preliminaries down to almost nothing is not necessarily better value — it may simply mean the cost turns up later as an extra, or that corners will be cut on protection and site management.
Provisional sums and where they belong
Some items genuinely cannot be fixed at quotation stage — an underground drain run of unknown condition, or a decorative allowance the client hasn't chosen yet. These are priced as provisional sums: a stated allowance clearly marked as subject to final measurement or client choice, rather than folded silently into the fixed price.
A quote with provisional sums is not automatically less reliable than one with none. What matters is whether every provisional item is clearly labelled, so the client knows exactly which figures might move and which are fixed.
Margin, risk and the final figure
On top of the measured cost sits a margin covering overheads and profit, and an allowance for risk on anything uncertain about the site or the client's brief. A contractor pricing a job with poor drawings, unclear access or a history of scope creep will price more risk into the figure than one pricing a well-documented, straightforward job.
This is why the same builder can quote very differently for two jobs of similar size — the risk sitting behind the number is doing as much work as the measured cost.
Common questions
Why do quotes for the same job vary so much between builders?+
Different builders may take off quantities from the same drawings differently, price labour at different output rates, include different levels of preliminaries, and carry different amounts of risk allowance. The totals reflect genuinely different assumptions, not just different profit margins.
Is a fixed price always better than an estimate?+
A fixed price gives certainty but only if it is built on a complete specification; a fixed price against a vague brief simply moves the uncertainty into variations later. An estimate against a clear scope, with provisional sums clearly marked, can be just as reliable.
Should preliminaries be shown separately on the quote?+
Ideally yes. Seeing scaffolding, skips, welfare and supervision as their own lines lets you compare like with like across quotes, rather than guessing whether they are included in the trade prices at all.
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We break the price down by trade, preliminaries and any provisional sums, so you can see exactly what you're paying for.