How to read a bill of quantities
A BOQ is a priced list of the work, written so that two people can compete on the same job. Reading one well is mostly knowing what it deliberately leaves out.
A bill of quantities is a list of every item of work on a project, each with a described scope, a unit, a quantity, a rate and an amount.
Its purpose is comparison. If two contractors are given the same list of items with the same quantities in the same units, then their totals mean something when set side by side, because they are pricing the same thing. Without it, every quotation is a different shape and comparing them is guesswork dressed up as procurement.
That is the whole idea. Everything difficult about a BOQ comes from the gap between that idea and a real site.
The anatomy of a line#
A single BOQ line has five parts, and people usually read two of them.
The item code. Boring, and the most useful thing on the page. It is what lets you follow one item from the estimate through the bill through the measurement sheet to the payment certificate. If your codes change between documents you have no thread to pull, and the same requirement on the accounts side is cost heads that survive a project.
The description. The actual contract. This is where the argument will happen. "Providing and laying" is a different scope from "laying". A description that names what is included and does not name what is excluded has told you very little.
The unit. Cubic metre, square metre, running metre, tonne, number, kilogram, quintal, lump sum. Read this before the rate, every time. A rate is meaningless without it, and mixed units within a bill are one of the most reliable sources of dispute there is — enough that we wrote about the unit of measure and where it leaks money on its own.
The quantity. Estimated, not guaranteed. More on this below, because it is the single biggest misunderstanding.
The rate. What the contractor is willing to do one unit of that item for, including everything the description says is included.
The quantity is an estimate#
This is the thing to internalise.
In most forms of measured contract, the quantities in a BOQ are the designer's best estimate of what the drawings imply. They are there so that tenders can be compared. They are not an order for that much work, and the contractor is not entitled to be paid for them if less work happens.
What gets paid is what gets measured, at the agreed rate, when the work is done. The bill provides the rate; the site provides the quantity.
This is why the difference between the quantity on paper and the quantity on the ground is a normal condition rather than a scandal — and also why it must be recorded rather than argued about later. That difference has its own piece: why measured and docketed quantities disagree.
Reading for what is missing#
An experienced reader spends most of their attention on absence.
- Is the preliminaries section priced, or spread? Site establishment, supervision, temporary works and insurance have to be paid for somehow. A contractor who prices them at nearly nothing has loaded them into the rates, which is fine as long as you know, and expensive to discover later if the quantities move.
- Which items have suspiciously high rates against small quantities? This is front-loading, and it is entirely rational behaviour. If a contractor expects a quantity to grow, they price that item high. Look at the items where the design is least settled.
- What has no line at all? The most costly omissions are the ones with no row to notice. Dewatering, shoring, disposal of excavated material, cutting and making good, testing. If it is not an item and not explicitly in a description, somebody will claim it as extra, and they will usually be right.
- Is there a provisional sum or a prime cost sum? These are placeholders for work that is not yet designed or priced. They are honest devices, but they are not commitments, and a total that leans heavily on them is a total that has not been fixed.
The rate is not the price#
A low rate on the biggest item wins tenders. Whether it survives contact with the site is a different question.
The useful discipline when comparing two bills is to ignore the totals for the first pass and compare rates item by item on the ten or fifteen lines that carry most of the money. Construction bills are extraordinarily top-heavy — concrete, steel, blockwork, finishes. If two bidders differ wildly on one of those lines, either one of them has misread the description or one of them knows something.
From the bill to the money#
The BOQ does not stop being useful once the contract is signed. It becomes the skeleton of every payment.
A running account bill is almost always the same list of items with a new column: quantity executed this period, cumulative quantity, cumulative value, less what was already certified. The clean version of that arithmetic depends entirely on the item codes staying constant. When somebody renumbers the bill halfway through a project, every cumulative figure in the file loses its meaning and has to be rebuilt by hand.
Retention, deductions, advances and set-offs all sit below that same structure. So the discipline of a well-formed BOQ pays out for the whole life of the job, and a sloppy one is paid for monthly, for years.
Three checks worth doing on any bill you are handed#
- Add it up yourself. Not to catch fraud. To catch a wrong formula in a spreadsheet, which is far more common and just as expensive.
- Pick five random lines and read the description out loud. If you cannot say what is included and what is not, neither can the person who will build it, and the gap between those two readings is the claim.
- Check that each unit matches its item. Reinforcement by weight, concrete by volume, formwork by contact area, painting by area, piling by length. A unit that does not match the physical nature of the work is usually a copy-paste error, and it will be found at measurement time by whichever party it favours.
The short version#
A bill of quantities is a fair way of asking several people the same question. It is not a forecast, not an order, and not a promise about how much work there will be.
Read the descriptions like a contract, the units like an engineer and the quantities like an estimate, and most of the surprises stop being surprises.