A bill of quantities is the document that turns a design into priced work. It lists what will be built, in what quantity, in what unit, and it gives every contractor the same basis to price. Without one, every quote is an opinion about a different building.
Most small builders never write one. They price from a drawing and a conversation, and the gaps surface later as variations. That is survivable on a single house where you are the client, and expensive on any project with a second party involved. This guide explains how to build a bill of quantities for a small building, from the structure of the document to the measurement rules, with a worked example of the main lines.
A bill is organised by work section, and each section contains measured items. Each item has four parts:
The structure usually follows the order of construction: preliminaries, groundworks, concrete, masonry, roofing, waterproofing, finishes, joinery, services, external works. Within each section, items are grouped so a contractor can price a trade in one pass.
Two things make a bill useful rather than decorative: the descriptions are unambiguous enough that different contractors price the same thing, and the quantities are measured by a consistent rule so a shortfall can be identified and corrected rather than argued about.
Consistency matters more than sophistication. Before measuring anything, decide these rules and write them at the front of the bill:
A bill without these five statements will be priced five different ways and argued over five different ways.
Preliminaries are the costs of doing the work rather than the work itself: site set-up, welfare, insurance, supervision, temporary power and water, scaffolding, security, cleaning at handover. On domestic work they are often 5-10% of the total, and on constrained urban sites more.
If preliminaries are not in the bill, they are in the rates invisibly, which means nobody can see them and nobody can challenge them. Give them their own section and let contractors price them openly.
Here is a practical bill structure for a single-storey two-bedroom house of about 95 m², with typical measured items:
Groundworks
Concrete
Masonry
Roofing
Finishes
Services
External works
Each of those items is one line. A house bill typically has 120-200 lines. That is not a bureaucratic artefact; it is the difference between a price that can be checked and a price that has to be trusted.
Take the external wall line, 12 m × 2.7 m with two windows and a door, in 215 mm blockwork:
Description: "Blockwork to external walls, 215 mm dense concrete blocks in cement mortar, including cutting, bonding, ties and all labours complete."
That description answers every question a contractor would otherwise ask: block type, thickness, mortar, and whether ties are included. A bill full of descriptions like "blockwork to walls" will be priced on assumptions that surface later.
Once the lines are measured, the bill supports three separate exercises:
A cost estimate using your own rates or local rates, which tells you whether the design fits the budget before you tender.
A tender, where contractors price the same lines and you compare like with like rather than comparing totals.
A payment schedule, where each line can be certified as it is completed, which is how a project avoids paying for work that has not happened.
The third use is the one small clients undervalue. A bill with 150 lines is also a progress checklist, and progress measured against quantities is far harder to dispute than progress measured against a percentage.
Each of these is arithmetic, not judgement. A second reviewer with a calculator catches most of them in an hour.
A spreadsheet is sufficient for a small building and better than most software, because the formulas are visible and can be checked. The structure that works:
The last point matters most. If the bill says 27.63 m² and nobody can see where 27.63 came from, the bill cannot be checked. Keep the measurement sheet, even after the project is finished; it is the record that answers a dispute two years later.
Some work cannot be measured before it starts: an unknown ground condition, a connection to an existing service, a repair that only becomes visible once a wall is opened. A bill handles these with three mechanisms, and using them correctly is what separates a professional document from a guess.
Provisional sums are allowances for defined work that is not yet measurable. The description must state what the sum covers, so a contractor does not add their own allowance on top.
Dayworks are for work that cannot be measured even in principle, priced by the hour at agreed rates with materials at cost plus a stated percentage. Keep daywork rates in the bill from the start; negotiating them mid-project gives away your position.
Contingency is the client's own reserve, not a contractor's line. Express it as a percentage of the measured total and keep it visible. On domestic work, 10% is a normal reserve for a straightforward build and 15-20% for renovation where existing conditions are unknown.
The estimating error that causes the most damage is using a provisional sum as if it were a price. A provisional sum of 5,000 for drainage is not a quote; it is a placeholder that will be replaced by a measured account.
A rate is not a price. It has five components, and a bill that separates them is easier to check than one that does not:
When you compare two rates for the same item, ask which of the five are included. A rate that looks 15% cheaper usually excludes plant or wastage, and that difference reappears as a variation or a slower programme.
Labour is the component that varies most between markets, which is why the same building costs different amounts in different countries even when materials are imported at similar prices. The FRELUX regional cost index exists for exactly this reason: a quantity is portable between markets, a rate is not.
The bill outlives the tender. During construction it becomes the schedule of work, the basis for interim payments, the record of variations and, at the end, the reconciliation between what was measured and what was built.
That requires one discipline: every change is recorded against the line it affects, with a date. A variation that is agreed verbally and measured later is a dispute waiting for a reason.
At completion, compare the final measured quantities with the original bill. The differences are your calibration data: if blockwork is consistently 6% above your measured quantities, your block-per-square-metre figure is wrong, and the next bill will be better for knowing it.
Is a bill of quantities the same as an estimate? No. A bill measures the work; an estimate prices it. The bill can exist without any rates at all.
How detailed should a small house bill be? Detailed enough that two contractors would price the same scope. For a 95 m² house, 120-200 lines is normal.
Do I need a bill for a renovation? Yes, and more than for new build, because existing conditions create provisional items and variations.
Who measures the quantities? Traditionally a quantity surveyor. On small projects, the designer or the client can measure them if the rules are stated and the calculations are kept.
Should rates be included in the document sent to contractors? No. Send quantities and descriptions, and ask for rates. Publish your own estimate separately if you have one.
What if the drawings change? The bill is revised, and the revision is dated. A bill that is edited silently becomes unusable as a record.
The FRELUX blueprint takeoff and BOQ tools measure from calibrated drawings and carry the quantities into a priced bill, so the measurement sheet and the priced schedule stay in one place. Start with the takeoff, add rates from the local price book, and the bill is ready to send.
A bill that is right in structure but wrong in quantity is worse than no bill, because it carries authority. Measure twice, write the calculation down, and keep the measurement sheet with the priced document so that anyone who questions a number can follow it back to a dimension on a drawing.