How to Read a Bill of Quantities Without a QS Background

Most clients see a Bill of Quantities for the first time when a contractor hands over a tender return, and most clients skim past it because it reads like an inventory list rather than a financial document. That's a mistake. The BoQ is the single document that tells you, line by line, what you are actually paying for and at what rate, which means it's also the document where a tender can quietly go wrong.

A standard BoQ is split into preliminaries, measured works, and provisional sums. Preliminaries cover the contractor's site costs that aren't tied to a specific building element: site office, insurance, security, temporary services. Measured works are the items you'd expect: concrete, blockwork, roofing, finishes, each quantified against drawings and priced per unit. Provisional sums are placeholders for work that hasn't been fully designed yet, such as a kitchen fit-out where the client hasn't chosen fittings.

The split matters because each section carries different risk. Preliminaries and measured works are firm prices once the contract is signed. Provisional sums are estimates that get adjusted, sometimes significantly, once the actual work is defined. A BoQ with an unusually high proportion of provisional sums is a BoQ where the final account is still largely undetermined.

Compare quantities against the drawings, not just the rates. A low rate against an inflated quantity produces the same total as a fair rate against the correct quantity, but only one of those is honest pricing. Round-number rates across many line items (every rate ending in 00 or 50) are worth a second look; real costing produces irregular numbers because materials, labour, and waste factors don't divide evenly.

Ask your quantity surveyor to walk you through the BoQ before you sign anything, not after. A twenty-minute conversation at tender stage is far cheaper than a dispute at final account stage over an item nobody understood when they signed off on it.