What Is a Bill of Quantities and Why Do You Need One?

Introduction

A bill of quantities, often referred to as a BoQ, is a detailed document used in the construction industry that itemises every material, labour element and cost component required to complete a building project. It is typically prepared by a Quantity Surveyor and is based on the architectural drawings and specifications for a project.

Think of a bill of quantities as a comprehensive shopping list for your entire build. Rather than guessing at costs or relying on a single lump-sum figure from a contractor, a BoQ breaks the project down into individual measurable items, each with a description, a quantity and a unit of measurement. This level of detail makes it possible to compare tenders on a like-for-like basis and manage costs throughout the construction process.

Whether you are a builder pricing a competitive tender, an architect advising a client on budget, or a homeowner trying to understand where your money is going, a bill of quantities is one of the most valuable documents you can have. In this guide, we explain what a BoQ contains, who uses one and how it can save you time, money and disputes on your next project.

What Does a Bill of Quantities Contain?

A well-prepared bill of quantities is organised by trade or work section, following a recognised method of measurement such as the New Rules of Measurement (NRM2) published by the RICS. Each section contains a list of measured items that together describe every piece of work needed to complete the project. Here is what you will typically find inside a BoQ:

• Preliminaries: These cover the contractor's general costs for running the project, including site setup, temporary facilities, site management, insurance, scaffolding hire and health and safety provisions. Preliminaries are not tied to a specific trade but apply to the project as a whole.
• Measured works by trade: This is the largest part of the document. Each trade section, such as substructure, superstructure, roofing, plumbing, electrical and finishes, contains individual items measured in the appropriate unit. For example, brickwork might be measured in square metres, concrete in cubic metres and drainage pipework in linear metres.
• Materials with quantities: Every item includes a clear description of the material or product to be used, along with the quantity required. This allows contractors to price each item individually and ensures that everyone is quoting for exactly the same specification.
• Labour allowances: While some BoQs include labour as a separate line item, it is more common for labour to be included within the rate for each measured item. The contractor includes their labour cost when pricing each line.
• Provisional sums: Where an element of the work cannot be fully defined at the time of tendering, a provisional sum is included. This is an estimated allowance for items such as unforeseen ground conditions, utility connections or specialist work that will be finalised during construction.
• Prime cost sums: These are allowances for items that will be supplied by a nominated supplier or subcontractor, such as a specific kitchen, sanitaryware or specialist cladding system. The contractor includes for fixing and any associated builder's work.

The level of detail in a BoQ means that nothing is left to assumption. Every element of the build is described, measured and priced, which provides a transparent and auditable record of costs from start to finish.

Who Uses a Bill of Quantities?

Bills of quantities are used by a wide range of people and organisations across the construction industry. While they are traditionally associated with larger commercial projects, they are increasingly used on domestic projects too, particularly where the client wants transparency and cost control.

Builders and contractors use bills of quantities to prepare accurate and competitive tenders. Because the BoQ defines exactly what is required, the contractor can focus on pricing the work rather than spending time measuring drawings and interpreting specifications. This speeds up the tendering process and reduces the risk of pricing errors or omissions.

Architects and designers often recommend that their clients commission a bill of quantities before going out to tender. It provides an independent cost benchmark that can be used to evaluate the quotations received and identify any items that have been over- or under-priced. Architects also find BoQs useful during the design stage for cost-checking different options and materials.

Property developers, housing associations and public-sector clients routinely require bills of quantities as part of their procurement process. For larger projects involving multiple tenderers, a BoQ ensures that all bids are based on the same scope of work, making the evaluation process fair and straightforward. Subcontractors also benefit from receiving a BoQ, as it clearly defines their scope and helps them price their element of the work accurately.

Benefits of Having a BoQ

Investing in a professionally prepared bill of quantities delivers a number of tangible benefits throughout the life of a construction project. Here are the key advantages:

• Fair tender comparison: When all contractors price the same BoQ, you can compare quotations on a genuine like-for-like basis. Without a BoQ, each contractor may interpret the drawings differently, include different items and present their prices in different formats, making meaningful comparison very difficult.
• Cost control: A BoQ provides a detailed cost baseline that can be tracked throughout the project. As work progresses, actual costs can be compared against the original priced items, giving early warning of any budget overruns.
• Change management: Construction projects frequently involve changes to the original design. When a BoQ is in place, the cost impact of any variation can be calculated quickly and accurately using the rates already agreed in the document. This avoids disputes and ensures that both parties have a clear basis for valuing changes.
• Dispute resolution: If a disagreement arises between the client and contractor about the scope of work or the value of completed elements, the BoQ provides a clear, agreed reference point. This can prevent minor disagreements from escalating into costly disputes.
• Payment milestones: The BoQ can be used to value work completed at each stage of the project, forming the basis for interim payment applications. This ensures that the contractor is paid fairly for work done, while the client only pays for work that has been completed.
• Future reference: A priced BoQ is an invaluable record for future maintenance, insurance valuations and any subsequent alteration work. It provides a detailed snapshot of what was built, how it was specified and what it cost.

In our experience, projects that use a bill of quantities from the outset run more smoothly, encounter fewer disputes and are more likely to finish on budget than those that rely on lump-sum quotations alone.

When Do You Need One?

While a bill of quantities is beneficial on almost any construction project, there are certain situations where it is particularly important or even essential. Understanding when to commission a BoQ will help you decide whether it is the right investment for your project.

Larger projects: For any project with a construction value above approximately £100,000, a BoQ is strongly recommended. The larger and more complex the project, the greater the potential for cost overruns and disputes, and the more valuable a detailed BoQ becomes as a control tool.

Competitive tenders: If you plan to invite multiple contractors to tender for your project, a BoQ is essential for ensuring a fair comparison. Without one, you may find it impossible to determine which quotation offers the best value, because each contractor will have priced a slightly different scope of work.

Publicly funded work: Public-sector projects, including those for local authorities, housing associations and government departments, almost always require a bill of quantities as part of the tender documentation. This is a governance requirement to ensure transparency and value for money.

Complex specifications: Projects with intricate design details, specialist materials or multiple services installations benefit greatly from the structured approach that a BoQ provides. It ensures that every element is captured and priced, reducing the risk of items being missed during tendering.

How We Produce Bills of Quantities

At First4Estimating, our qualified Quantity Surveyors prepare bills of quantities to a high professional standard, following the New Rules of Measurement (NRM2) published by the RICS. Our process is thorough, efficient and designed to give you a document that is ready to issue to tenderers with confidence.

The process begins when you send us your drawings and any supporting specification documents. Our QS team reviews the information, clarifies any queries with you or your design team, and then carries out a full take-off of quantities from the drawings. Every element of the build is measured, described and organised into the appropriate trade sections.

Once the measurement is complete, we compile the BoQ into a clear, professionally formatted document that contractors can price easily. We include all necessary preliminaries, provisional sums and prime cost items, along with notes and preambles that define the standard of workmanship and materials required.

We typically turn around a standard domestic bill of quantities within five to seven working days, and larger commercial projects within two to three weeks depending on complexity. If you need your BoQ on an expedited timescale, we can often accommodate this with advance notice.

To find out more about our BoQ and estimating services, visit our estimating services page or contact our team to discuss your project. We are happy to provide a fee quotation before you commit.