If you are planning a construction project in the UK, you will almost certainly encounter a JCT contract. The Joint Contracts Tribunal produces the most widely used standard form building contracts in the country — but with dozens of different forms available, choosing the right one can feel bewildering.

This guide cuts through the complexity and explains the most commonly used JCT forms in plain English.

Why Use a Standard Form Contract at All?

Before we get to the specific forms, it is worth understanding why standard contracts exist and why you should use one.

A building contract defines the legal relationship between you and your contractor. It sets out what is to be built, for how much, by when, and what happens if things go wrong. Without a contract — or with a poorly drafted one — you have very limited protection if the contractor fails to perform, goes over budget, or disputes arise.

Standard JCT forms have been developed and refined over decades. They are familiar to contractors, consultants, and the courts. Using a standard form means that the risk allocation, payment mechanisms, and dispute resolution procedures are well understood by all parties — which reduces the scope for disagreement and makes disputes easier to resolve when they do arise.

Never sign a contractor's own terms and conditions without having them reviewed by a professional. They will almost invariably favour the contractor.

The Main JCT Forms

JCT Minor Works Building Contract (MW)

Best for: Straightforward projects up to approximately £250,000

The Minor Works contract is the simplest JCT form and the most commonly used on smaller residential projects. It is appropriate where:

• The works are straightforward and well-defined
• The design is complete before the contractor starts on site
• A Contract Administrator (architect or QS) is appointed
• The programme is relatively short

Minor Works uses a simple payment mechanism — interim valuations at agreed intervals — and has a streamlined variation and claims process. It is not suitable for complex projects, phased works, or where the contractor has any design responsibility.

JCT Intermediate Building Contract (IC)

Best for: Projects from approximately £250,000 to £2m

The Intermediate contract sits between Minor Works and the full Standard form. It is appropriate for more complex projects where:

• The works involve multiple trades and a more detailed specification
• A more robust payment and variation mechanism is required
• The programme is longer and requires more active management
• There may be named subcontractors

The IC form includes more detailed provisions for extensions of time, loss and expense claims, and practical completion — making it better suited to projects where these issues are more likely to arise.

JCT Standard Building Contract (SBC)

Best for: Larger or more complex projects above £2m

The Standard Building Contract is the most comprehensive JCT form and is used on larger, more complex projects. It comes in several variants:

• SBC/Q — with quantities (a bill of quantities forms part of the contract)
• SBC/XQ — without quantities (a schedule of works or specification is used instead)
• SBC/AQ — with approximate quantities (used where the scope is not fully defined at tender)

The SBC includes detailed provisions for all aspects of the contractual relationship and is appropriate where the financial and programme risks are significant enough to warrant the additional administrative overhead.

JCT Design and Build Contract (DB)

Best for: Projects where the contractor takes responsibility for design

The Design and Build contract is fundamentally different from the other forms. Under a D&B contract, the contractor is responsible for both the design and the construction of the works. The client provides an Employer's Requirements document setting out what they want, and the contractor responds with a Contractor's Proposals.

D&B contracts are popular with developers and commercial clients because they provide a single point of responsibility and greater cost certainty. However, they require careful management — the client appoints an Employer's Agent rather than a Contract Administrator, and the design quality can suffer if the Employer's Requirements are not sufficiently detailed.

JCT Homeowner Contracts

Best for: Domestic clients without professional advisers

JCT produces two contracts specifically for homeowners: the Homeowner Contract (for use with a consultant) and the Building Contract for a Home Owner/Occupier (for direct use without a consultant). These are simpler documents designed to be used without professional support, though we would always recommend appointing a QS or CA even on smaller projects.

Key Contract Terms to Understand

Whichever form you use, there are several key terms that every client should understand:

Practical Completion — the point at which the works are substantially complete and the building can be occupied. This triggers the release of half the retention and starts the defects liability period.

Defects Liability Period — typically six to twelve months after practical completion, during which the contractor is obliged to return and remedy any defects that emerge. The remaining retention is released at the end of this period.

Retention — a percentage of each interim payment (typically 3–5%) withheld by the client as security against defects. Half is released at practical completion; the remainder at the end of the defects liability period.

Liquidated Damages — a pre-agreed sum per week that the contractor pays if they fail to complete by the contract completion date. These must be a genuine pre-estimate of the client's loss to be enforceable.

Extensions of Time — provisions allowing the contractor to claim additional time (but not necessarily money) where delays are caused by events outside their control, such as exceptionally adverse weather or client-instructed variations.

Getting the Contract Right

Choosing the right contract form is important, but it is only the starting point. The contract also needs to be properly completed — with realistic dates, appropriate retention and liquidated damages figures, and any necessary amendments to the standard terms.

A QS or Contract Administrator should review the contract before it is executed, ensuring that the commercial terms are appropriate for your project and that you understand your obligations as a client.

If you would like advice on the right contract form for your project, we are happy to help.