Bill of quantities: pricing the same job the same way twice

A bill of quantities is an itemised schedule of the materials, labour and works needed to build something, measured from the drawings and specification, with a quantity and a unit against every item and a space for the contractor to insert a rate. It is issued with the tender documents so that every bidder prices the same scope in the same order.

That comparability is the point. Without a bill, each tenderer measures the job themselves, and the client receives lump sums that cannot be compared — the cheapest may simply have missed something. With a bill, the client compares rate against rate and can see exactly where a bidder is expensive and where they are suspiciously cheap.

What a bill of quantities contains

• Preliminaries: site setup, management, insurances, temporary works — costs that belong to the project rather than to any measured item.
• Measured works, grouped by trade or element, each with a description, unit and quantity.
• Provisional sums for work that is known to be needed but not yet defined.
• Prime cost sums for items to be supplied by a nominated party.
• Dayworks rates, for work that has to be valued on time and materials.
• Contingency, where the contract provides for one.

Descriptions have to be precise enough to price: the unit of measurement, the material, the finish, the constraint. "Blockwork, m²" is not pricable; the same item with thickness, block type, mortar and whether it is above or below ground is. Vague descriptions do not save time — they produce qualified bids and arguments later.

Measurement rules are not optional

Quantities are measured under a standard method — NRM in the UK, CESMM for civil engineering, POMI or a local equivalent elsewhere — and the bill states which. The method decides what is measured net and what includes waste, what is deemed included in a rate, and how items are grouped. A bill that does not name its method leaves every rate open to a different reading.

A bill of quantities does not usually override the drawings and specification: those define the work, and the bill measures it. Where the contract makes the bill part of the contract documents, an error in quantity becomes a valuation matter rather than the contractor’s risk — which is exactly why the priority of documents clause is worth reading before tendering.

Where the bill earns its keep

1. Tender comparison: rates line up against each other, so an outlier is visible instead of buried in a lump sum.
2. Interim valuation: work done is measured against bill items, so payment applications have a basis both sides accept.
3. Variations: when the scope changes, the contract usually values it using rates already in the bill — which means the rates agreed at tender govern work nobody had thought of yet.
4. Final account: the measured bill is the starting point for agreeing what was actually built.
5. Cost planning on the next project, because a priced bill is a record of what things actually cost here.

The third item is where money is won and lost. A rate that looked generous at tender becomes the price of every similar variation for the life of the job, and an unbalanced bill — high rates on early items, low on late ones — changes the contractor’s cash flow long before anyone notices.

Keeping the bill workable

A bill is a spreadsheet with a contractual life: it is priced by several people, revised during tender, then referenced for two years while the job runs. Ettex Sheets keeps the priced version, the addenda issued during tender and the measured quantities in one place with their history, so the rate someone quotes in a variation dispute can be traced to the version it came from. The same discipline that a bill of materials needs on the manufacturing side applies here — one schedule, versioned, not a folder of near-identical files.

Where the tender is run properly, the bill also sits at the centre of the procurement process: issued to all bidders at once, amended only by formal addendum, and returned priced in the same structure it went out.