Most construction disputes were decided before work started.
By the time a dispute surfaces on a UK construction project, the outcome is often already determined. Not by what happened on site, but by what the contract said, and more importantly, by what it did not say clearly enough.
A JCT contract is not a formality. It is the commercial framework that governs every payment, every variation, every delay and every final account negotiation on the project. Signing it without a clear commercial reading of its key provisions is one of the most expensive decisions a developer or investor can make.
This is not about legal advice. It is about understanding what you are agreeing to commercially before the contractor starts work.
What a JCT contract is and why it matters commercially.
JCT stands for the Joint Contracts Tribunal. It produces a suite of standard form construction contracts widely used across the UK, covering everything from minor works to large-scale design and build schemes. Most UK residential developers, investors and main contractors will encounter a JCT form at some point in their programme.
The JCT suite covers several different contract forms, each suited to a different procurement route. The Standard Building Contract allocates design responsibility to the employer. The Design and Build Contract transfers it to the contractor. The Management Building Contract structures the project through trade contractors. Each form carries a different commercial risk profile and requires a different approach to cost management, procurement and independent QS oversight.
Choosing the wrong form, or using the right form with poorly considered amendments, is one of the most common sources of commercial exposure on UK construction projects. We see the consequences directly in the projects we engage on at contract interpretation disputes and scope definition risk stage.
The clauses that carry the most commercial risk.
Not every clause in a JCT contract carries equal weight commercially. In our experience working across UK construction projects, the provisions that generate the most disputes are consistently the same ones.
The variations clause defines what constitutes a variation and how it is valued. On a Design and Build contract, this is particularly important because the contractor controls the design development. If the variations clause is not tightly drafted, almost any change the contractor makes to the design can be presented as a client instruction rather than a contractor obligation.
The loss and expense clause governs what the contractor can claim if they are disrupted or delayed by events that are the client’s responsibility. Poorly drafted preliminaries and an unclear programme baseline make loss and expense claims very difficult to challenge. This feeds directly into the acceleration pressure and programme sequencing risk scenarios we handle regularly.
The payment provisions set out when and how the contractor applies for payment, how long the client has to respond and what happens if neither party issues the required notices. The Construction Act requirements around payment notices and pay less notices are not optional. Missing them has immediate financial consequences.
The practical completion clause determines when the contractor’s main obligations end, when retention is released and when the defects liability period begins. Vague drafting around what constitutes practical completion is one of the most consistent sources of end-of-project disputes on UK schemes.
What to look for before you sign
Before executing a JCT contract on a UK construction project, a commercially focused review should cover at minimum the following areas.
The scope of works needs to match the tender documents precisely. Any discrepancy between what the contract says and what the contractor priced creates immediate ambiguity about what is and is not included in the contract sum. This is the foundation of most tender documentation gaps disputes.
The contract sum analysis needs to be structured so that variations can be valued clearly. A poorly structured contract sum analysis makes every variation a negotiation rather than a calculation.
The programme needs to be incorporated into the contract with sufficient detail to establish a baseline. Without a contractual programme, delay and disruption claims have no reference point.
The insurance and liability provisions need to reflect the actual risk profile of the project, particularly on high-end residential schemes and complex refurbishment projects where the consequences of defects or damage are significant.
Any bespoke amendments need to be read in the context of the standard form provisions they modify. Amendments that appear to protect the client can inadvertently create gaps or inconsistencies elsewhere in the contract.
Why independent commercial review matters here.
A solicitor reviews a JCT contract for legal risk. An independent QS reviews it for commercial risk. Both perspectives are necessary. Neither replaces the other.
Commercial review focuses on whether the contract creates a sound basis for cost management, variation assessment and final account negotiation. It asks whether the provisions support Construction Cost Control throughout the project or undermine it. It identifies where the drafting creates exposure that will cost money to resolve and recommends adjustments before the contract is signed rather than after the first dispute arises.
At Reltic, we provide this review as part of our broader commercial engagement across the project lifecycle, from early Digital Cost Planning and Strategic Procurement through to Final Account and Dispute Support. The contract is the framework within which all of that work happens. Getting it right at the start makes everything that follows more straightforward.
What to do next
If you are approaching contract execution on a UK construction project and have not had the JCT terms reviewed from a commercial perspective, the cost of doing so is a fraction of what a single disputed clause will cost to resolve.
You can read more about our approach to Strategic Procurement and Construction Cost Control, or see how contract structure connects to Variation and Change Control and Final Account and Dispute Support.
If you would like us to review a specific contract or advise on a procurement structure before you commit, get in touch with Reltic directly. We can identify the commercial risks in your current documentation and recommend a position that protects you throughout the project.
