A Bill of Quantities, usually called a BOQ, is a structured document that describes and measures the work required for a construction project. It breaks the project into identifiable items, such as excavation, concrete, brickwork, roofing, windows, finishes and services, so contractors can price the same scope on a like-for-like basis.
A BOQ is normally prepared from the drawings, specifications and other project information. In the UK, the RICS New Rules of Measurement provide recognised measurement guidance for construction cost management. The suite includes NRM 1 for order of cost estimating and cost planning, NRM 2 for detailed measurement for building works, and NRM 3 for maintenance works. Read the RICS NRM information.
What does a BOQ normally contain?
The exact format depends on the project and procurement route, but a useful BOQ commonly includes:
- Preliminaries: project-wide items such as site set-up, management, temporary works, welfare, protection and general obligations.
- Measured work sections: descriptions of the work, quantities and units of measurement, arranged in a logical order.
- Materials and workmanship requirements: references to drawings, specifications, performance requirements or stated standards where these affect the price.
- Provisional or undefined items: allowances for work that cannot yet be fully described or measured, where these are appropriate.
- Contractor pricing columns: spaces for unit rates, item totals, adjustments and the overall tender total.
- Preliminaries, overheads and other pricing information: depending on the document and the contract arrangements.
The purpose is not simply to list materials. A proper BOQ measures the work needed to complete the defined scope. It should also make clear what is included, what is excluded and which assumptions have been made.
How is a BOQ different from an early cost estimate?
An early cost estimate is a forecast made while the project is still being developed. It may use approximate areas, historical data, benchmarks, rates or outline assumptions. It helps answer questions such as: “Can we afford this scheme?” or “Should we proceed with this option?”
Cost estimates should not be treated as permanently fixed figures. Government cost-estimating guidance explains that an estimate develops as the project scope and programme mature, and that it should reflect risk and uncertainty rather than presenting false precision. See the GOV.UK Cost Estimating Guidance.
A BOQ is generally more detailed and is normally prepared later, when the design and specification contain enough information to measure the work properly. It can support tendering, but it does not remove the need for an earlier budget estimate. In practice, the estimate helps establish the budget; the BOQ helps define and compare the priced work.
How is a BOQ different from a material take-off?
A material take-off is a list or calculation of materials and quantities needed for construction. For example, it might identify the number of bricks, metres of timber, sheets of plasterboard or cubic metres of concrete.
A BOQ is broader. It normally describes the work activity, not just the material. A brickwork item may need to allow for labour, mortar, access, cutting, waste, plant and the specified construction method, depending on the measurement and pricing rules being used. A material take-off can therefore be useful for purchasing and internal planning, while a BOQ is more suited to obtaining and comparing complete construction prices.
When is a BOQ useful?
For tendering a defined design
A BOQ is most useful when you have a reasonably complete set of drawings and specifications and want several contractors to price the same scope. Each tenderer receives the same measured items, which reduces the risk that one contractor has allowed for work another has missed.
This is particularly helpful for extensions, refurbishments, new-build homes and small developments where the work is substantial enough for differences in scope to have a material effect on the final price.
For comparing tenders
With a consistent BOQ, you can compare unit rates and item totals rather than looking only at the final lump sum. Large differences can then be investigated. A contractor may have misunderstood a specification, omitted an item, made a different allowance or identified a genuine construction risk.
Comparison should still be carried out carefully. A low tender is not automatically the best tender. Check qualifications, exclusions, programme assumptions, provisional sums, VAT treatment, design responsibility and whether the contractor has priced every item.
For cost control during the works
A BOQ can provide a baseline for assessing progress payments, variations and the financial effect of design changes. If the scope changes, the relevant measured item can often be adjusted or replaced more transparently than an unexplained change to a single lump sum.
It can also help the project team track which parts of the budget are committed, which are still to be procured and where quantities or design decisions need attention.
What can a BOQ not guarantee?
A BOQ does not guarantee a final project cost, a fixed completion date or a trouble-free build. It is only as reliable as the information used to prepare it and the assumptions recorded within it.
Costs may change because of design development, client changes, unforeseen ground or existing-building conditions, statutory requirements, supply issues, access restrictions, inflation, contractor methodology or omissions in the underlying information. A BOQ can make these matters easier to identify and value, but it cannot eliminate them.
It is also not a substitute for a suitable building contract, properly coordinated design, site investigation, technical advice or competent project administration. Government guidance stresses the importance of documenting assumptions, exclusions, evidence and risk, and of reviewing estimates as the project develops. Those principles are relevant when using a BOQ as part of cost control. Review the guidance on assumptions, risk and estimate maturity.
What information is needed before preparing one?
The more complete the project information, the more useful the BOQ is likely to be. Depending on the work, this may include:
- Architectural, structural and engineering drawings.
- Written specifications and schedules of finishes.
- Site measurements, surveys and information about the existing building.
- Ground investigation or drainage information where relevant.
- Planning conditions, building control requirements and client standards.
- Information about access, working hours, neighbour constraints and phasing.
- A clear description of client-supplied items, contractor-designed elements and exclusions.
- The proposed procurement route and form of contract, if already selected.
If important information is missing, the right response may be an early cost plan, an approximate estimate or a list of information gaps rather than a detailed BOQ. An experienced quantity surveyor or estimator can advise on the appropriate level of detail for the project stage.
Do you need a BOQ?
A BOQ may be worthwhile if you are inviting several contractors to tender, managing a substantial alteration or development, or need a clear basis for valuing changes and payments. It may be unnecessary for a small, straightforward job where the scope is fully understood and a reputable contractor is providing a detailed quotation.
For complex or uncertain work, do not wait until tendering to think about cost. Early budgeting, scope definition and risk review can prevent the design from progressing beyond what the available budget can support. The government guidance describes estimating as an evolving process linked to scope and programme, while RICS identifies separate measurement and estimating approaches for different stages of construction cost management. See how the RICS NRM suite separates estimating and detailed measurement.
If you would like help choosing the right estimating approach, tell us about your project and we can point you towards a practical next step.
Short decision checklist
- Is the design sufficiently developed? If not, start with an estimate or cost plan and record the assumptions.
- Will several contractors price the work? A BOQ can make tender comparisons more consistent.
- Is the project large or complex enough to justify detailed measurement? Consider the value of clearer scope and change control against the preparation cost.
- Are existing conditions or design responsibilities unclear? Resolve these where possible, or clearly identify allowances and exclusions.
- Do you need structured valuation of progress and variations? A BOQ may provide a useful contract administration baseline.
- Would specialist advice reduce risk? For substantial, unusual or high-risk work, obtain advice from a suitably experienced quantity surveyor, estimator or design professional.
The best document is not necessarily the longest one. A BOQ should match the quality of the design information, explain its assumptions and provide a practical basis for pricing and cost control.
