JCT Contracts Explained: The Key Clauses Every Contractor Should Actually Understand
JCT Contracts Explained: The Key Clauses Every Contractor Should Actually Understand
If you’ve worked in construction for more than a week, you’ve probably had a JCT contract slide across your desk. Sometimes it’s in a smart binder. Sometimes it’s a PDF someone’s “tidied up” with their own amendments. And sometimes it’s printed in a hurry on a site printer that’s been out of toner since 2019.
However it arrives, most contractors do the same thing: they glance at the front page… flick to the price… skim for the programme dates… and hope the rest never becomes their problem.
But of course, it always becomes your problem. Usually at the worst possible moment.
So, in the spirit of keeping things simple, straight‑talking, and grounded in the real day‑to‑day of construction — much like Manchester’s own story of growth and graft — here’s a Plain English guide to the JCT clauses that actually matter. No jargon. No legal lectures. Just the stuff that keeps projects running, payments flowing, and relationships intact.
Why JCT Still Matters in 2026
The Joint Contracts Tribunal (JCT) produces the most widely used standard forms of building contract in the UK. That isn’t marketing — it’s simply how the industry runs today.
Over the last two years, JCT has rolled out its 2024 Edition, modernising the suite with changes like clearer drafting, email notices, updated building safety obligations, and new grounds for delay such as epidemics and certain ground‑condition risks.
In other words, the JCT you’re working under now isn’t quite the JCT you learned as an apprentice.
It’s evolved — largely because construction itself has been through a turbulent decade. Supply chain squeezes, new safety laws, inflation, and a sharp uptick in disputes have all left their mark. JCT’s updates reflect this reality.
So let’s break down what contractors actually need to understand.
1. Payment Clauses: The Beating Heart of Cashflow
Ask any contractor what keeps them up at night and it’s rarely design philosophy or the nuances of subcontracting. It’s getting paid — properly and on time.
JCT payment clauses sit on top of the Housing Grants, Construction and Regeneration Act 1996, which lays down strict rules for fair payment:
- clear due dates
- clear final dates for payment
- a payment notice within 5 days
- and rules around pay less notices.
If the contract doesn’t meet these standards, the Scheme for Construction Contracts steps in automatically.
In practice, this means:
If a payment notice is late or missing, your application can become the “notified sum.”
Contractors are often surprised at how strict courts have become on this point. Recent commentary explains that even small errors in notice timing can swing an adjudication.
**And if there’s no valid pay less notice?
The full notified sum must be paid — even if the number is wrong.**
This creates the classic “smash‑and‑grab” scenario. It’s not about fairness; it’s about the rules. Knowing these rules keeps cashflow moving — and keeps your business alive.
2. Variations: Where 90% of Arguments Begin
Every construction project changes. Sometimes it’s because the client tweaks their idea. Sometimes it’s because something unexpected appears behind a wall. Sometimes it’s because the original drawings came straight from the land of make‑believe.
Under JCT, variations (or “Changes” in the DB form) need to be:
- clearly instructed
- properly valued
- properly evidenced
The contract gives a structured process: written instructions, valuation rules, and — importantly — the right to confirm verbal instructions in writing if the employer fails to do so.
But here’s the modern twist:
Courts are increasingly treating written‑instruction requirements as conditions precedent.
Meaning:
If it’s not instructed properly, you might not get paid for it.
Recent analysis shows courts leaning towards enforcing these formality rules strictly, following the logic from the Supreme Court’s Rock Advertising case on “no oral variations.”
Moral of the story:
Put it in writing. Then put it in writing again.
3. Extensions of Time: The Rules Have Tightened
The 2024 updates didn’t just modernise language; they changed timelines too.
Employers now often have 8 weeks instead of 12 to assess extension‑of‑time (EoT) claims.
That’s good news for contractors because it speeds up clarity. But it also means your notices must be:
- early
- detailed
- evidenced
- and regularly updated
The list of Relevant Events has also expanded. Things like:
All now fall within the JCT’s delay mechanism — provided the issue wasn’t already flagged in the documents.
This is a big deal, contractors now have clearer contractual routes for real‑world problems that have caused expensive disputes over the last decade.
Well at least on unamended forms!
4. Loss and Expense: The Rules Are Stricter Than You Think
Loss and Expense (L&E) covers the actual financial impact of employer risk delays — extra prelims, labour inefficiencies, longer supervision, plant, financing costs, and more.
But contractors often fall into the trap of thinking L&E will be sorted out at the final account.
Unfortunately, JCT doesn’t work that way.
Under most amended 2016 and 2024 forms, recent Scottish and English cases suggest the L&E notification clause may operate as a condition precedent — meaning if you don’t notify early and properly, you could lose entitlement entirely.
And even if you notify on time:
You must usually provide serious evidence — not a spreadsheet of guesses.
Full labour records, timesheets, allocation sheets, plant logs, delay narratives — all essential. As one detailed practitioner guide notes: a simple summary is “not adequate.”
It’s painful admin. But it’s cheaper than losing a £150,000 claim because you “planned to pull it together later.”
5. Design Responsibility: Read This Twice If You’re Under a D&B Contract
Design responsibility is one of the most misunderstood areas in construction — and the one that lands contractors in court most often.
Under unamended JCT Design & Build:
- The contractor must exercise reasonable skill and care
- Fitness‑for‑purpose is expressly excluded in the 2024 edition
That sounds reassuring… until you see your client’s 48 pages of bespoke amendments.
In the real world, many employers rewrite the risk allocation to push:
- full design responsibility
- responsibility for verifying the adequacy of the Employer’s Requirements
- and liability for any design gaps, however early in the process
Case law and commentary show this is becoming increasingly common — and courts will enforce these amendments if you’ve signed them.
And then there’s the Contractor’s Design Portion (CDP) on traditional forms. Think of CDP as a mini D&B package inside a larger traditional contract.
CDP works brilliantly when well‑defined.
But when it isn’t?
It becomes, as one expert put it, a “dumping ground for unresolved risk.”
6. Liquidated Damages: Not the Scary Beast They Used to Be
Liquidated damages (LDs) have been through a dramatic evolution thanks to the Supreme Court’s decision in Cavendish v Makdessi.
Here’s the modern rule:
LDs are enforceable as long as they protect a legitimate commercial interest and aren’t wildly excessive.
It’s no longer about whether they represent a “genuine pre‑estimate of loss.”
For contractors, this means:
- Most LD clauses will stick
- Employers don’t need to prove actual loss
- Your best protection is a realistic programme and early delay notices
On the bright side, the Supreme Court’s Triple Point ruling now firmly establishes that LDs run up to termination, and after that point, general damages take over — which JCT 2024 guidance reflects.
7. Termination Clauses: The 2026 Supreme Court Case Every Contractor Should Know
A landmark 2026 decision — Providence Building Services v Hexagon Housing Association — has settled a long‑running debate around termination for repeated default under JCT DB.
To put it simply:
You cannot terminate immediately for a repeated late payment unless the first late payment lasted long enough to create a termination right.
The Supreme Court held that clause 8.9.4 is “parasitic” on clause 8.9.3 — meaning the first breach must mature into a termination right before a second breach can trigger immediate termination.
This overturns a worrying Court of Appeal interpretation and restores the traditional stepped structure contractors have relied on.
It’s a win for clarity — but it also reminds contractors:
Termination is a technical minefield.
One wrong step can flip you from aggrieved party to guilty of repudiatory breach.
8. Adjudication: The 28‑Day Process
When a dispute breaks out, adjudication is usually the first stop, most times the only stop. JCT incorporates the statutory right to adjudicate under the Construction Act, and the process is designed to be fast and practical.
Key features include:
JCT (and RICS) publish simplified adjudication rules for homeowner contracts, which echo the same principles contractors see under commercial forms.
Adjudication is quick, rough‑and‑ready, and reliant on documentation more than drama. If your notices and records are tight, you stand a fighting chance.
9. Building Safety Act: JCT Now Acknowledges the New World
The 2024 edition now requires parties to identify the Principal Designer and Principal Contractor, recognising the dutyholder roles created by the Building Safety Act 2022.
But don’t be fooled:
For higher‑risk buildings (HRBs), you will still need project‑specific amendments covering Gateways and the Golden Thread.
JCT hasn’t done that work for you.
10. Collaboration, Sustainability, and “Good Faith”: Now Core Contract Duties
The 2024 update elevates previously optional provisions on:
- collaborative working
- sustainability
- early dispute notification
These are no longer fringe ideas — they’re core articles and conditions. Commentators note the industry welcomes the shift even if the practical impact remains to be seen.
In a world increasingly shaped by net‑zero commitments and tighter regulatory oversight, these clauses set expectations for behaviour, not just outcomes.
If you’re dealing with a construction issue and need expert input — or just want to understand your options — we’d love to hear from you.
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