If you’ve ever spent time on a construction site or in a design team meeting, you’ll know that progress isn’t just about technical know-how; it’s about trust, timely information, and people talking to one another. When someone drops the ball, everyone feels it. Sometimes, the consequences are not just costly, but they can also lead to legal wrangling.

In this industry, interdependence isn’t a buzzword; it’s the reality that underpins every project. From my experience as an expert witness, I’m usually brought in when that interdependence breaks down, and the fallout can be significant for everyone involved.

Interdependence in Practice

Complex projects are a system of systems. Architectural intent, structural design, building services, fire and life safety, façade, geotechnical, and digital engineering all interlock. Trade contractors and suppliers implement and prove performance. If interfaces are unclear, design maturity is uneven, or specialist inputs are engaged too late, risk escalates, leading to rework, delay, and disputes.

Industry evidence backs this up. The CRUX 2025 dataset, covering more than 2,200 projects worldwide, reveals that sums in dispute average 33% of the contract value and claimed extensions of time at 66% of planned schedules, with design and coordination failures prominent, especially when teams attempt to “speed the build.” These aren’t abstract numbers; they reflect the real cost of under-managing interdependence.

“If interfaces are unclear, design maturity uneven, or specialist inputs engaged too late, risk escalates, leading to rework, delay, and disputes.”

What the Courts Expect

Recent legal decisions increasingly recognise the realities of how interdependent our projects have become. Recent cases highlight the importance of clarity, responsibility, and proactive management. Key lessons include:

Workman Properties Ltd v ADI Building & Refurbishment Ltd [2024] EWHC 2627 (TCC)

Lesson: If you undertake to complete and verify design under an amended JCT DB contract, a single sentence in the Employer’s Requirements won’t shield you from responsibility. Consistency across the contract suite is essential. Interdependent teams must check the design before proceeding.

BNP Paribas Depositary Services Ltd v Briggs & Forrester Engineering Services Ltd [2024] EWHC 2903 (TCC)

Lesson: Accepting full design responsibility can include existing site conditions. Suspending or terminating work without properly owning those risks may amount to a repudiatory breach. Safety-critical upgrades necessitate a comprehensive, whole-system approach across all interfaces.

Building Safety Act 2022 (and Willmott Dixon Construction Ltd v Prater & Ors [2024] EWHC 1190)

Lesson: With the introduction of the Building Safety Act (BSA) and recent case law, we’re seeing broader duties and longer periods during which claims can arise decades after completion. Building Liability Orders can extend responsibility to related companies. This shift means that it is more important than ever to maintain thorough records (from design decisions to compliance checks), as these documents may be called upon long after the project handover.

The Interdependence Framework

Lessons from disputes and industry data demonstrate that a clear, deliberate, structured approach is needed if we want to avoid repeating the same mistakes. Below are practical steps to help teams manage interdependence effectively and reduce the risk of disputes at every stage of a project.

A) Contract & Responsibility Mapping (before design)
Start by ensuring roles and responsibilities are clearly defined and aligned across all project documents.

• Define “design completion” explicitly. Align responsibilities across Employer’s Requirements, schedules, and bespoke amendments.
• Set a document hierarchy. Clarify how performance obligations (e.g., design life, standards) interact with general duties.
• Establish reliance pathways. Confirm who may rely on which reports; obtain assignments/consents for third-party data.
• Plan the compliance trail. Under the BSA, keep decisions, calculations, test evidence, and change logs accessible and complete.

B) Collaboration & Programme Management (before you procure)
Early and ongoing collaboration is crucial to managing risk and ensuring the smooth delivery of projects.

• Engage specialists early. Fire, façade, controls/BMS, smoke modelling, acoustics, and geotechnical should be brought in before design freeze.
• Run an interface register with RACI (Responsible, Accountable, Consulted, Informed). A living matrix that names owners, inputs/outputs, acceptance criteria, and dates.
• Govern the model. BIM change control, traceable RFIs, no “shadow drawings,” and interface signoffs before IFC release.
• Gate the programme. Hold cross-discipline reviews at 30%, 60%, and 90% design; use hold points before ordering long-lead items.

C) Assurance & Commissioning (before handover)
As projects near completion, the importance of robust assurance and commissioning processes cannot be overstated. This stage is where the effectiveness of earlier collaboration and coordination is truly put to the test. Ensuring that systems work together as intended and that all interfaces are closed and documented protects all parties from future disputes and operational failures.

• Scenario testing. Cause & Effect and failure scenario testing (e.g., power loss, smoke control); witness tests with photo/video records.
• Evidence packs. Assemble certificates, calibration sheets, and compliance documents that are fit for audit and legal scrutiny.
• Interface closure. Confirm physical and digital interfaces are locked, documented, and accepted by all affected parties.

“… the issues that lead to claims and litigation could have been avoided with better consideration and coordination early in the process.”

Role‑Specific Action Points

Everyone involved in a construction project, whether client, designer, or contractor, has a distinct part to play in making collaboration work. Time and again, CRUX data and my own experience have shown that many disputes could have been avoided with clearer coordination and responsibilities agreed from the outset. When each party takes ownership of their role and makes the effort to engage early, the whole team stands a much better chance of steering clear of unnecessary risk and delivering a successful project.

Employers/Clients
The foundation for successful interdependence is laid at the outset. This means structuring contracts, project management, programme management, and design processes to actively foster collaboration and recognise the interconnectedness of all contributors. Learning from the patterns highlighted in CRUX data, clients should require early specialist engagement, mandate the use of a formal interface register, and insist on BIM governance as part of the deliverables. Incentivising design maturity before starting on site by setting hold points and quality gates tied to payment milestones can help embed collaboration into the project’s DNA, reducing the likelihood of disputes later.

“The reality, as CRUX data highlights, is that many disputes stem from late or incomplete design information.”

Designers (Lead and Specialists)
From my own time working as a designer, I know that managing interfaces is about far more than producing drawings. It means keeping an eye on what’s happening both upstream and downstream, double-checking the information you’re given, and speaking up early when you spot gaps or inconsistencies. The reality, as CRUX data highlights, is that many disputes stem from late or incomplete design information. Good designers don’t just focus on their own discrete disciplines; they make sure their work fits the bigger picture, stays within budget and performance targets, and they’re not afraid to raise the alarm if something doesn’t add up.

Regular cross-disciplinary design reviews are invaluable, not only for ensuring that all interfaces are covered and requirements properly understood, but also to demonstrate how much each discipline depends on others. Scenario testing and keeping a clear record of decisions and assumptions are also essential. This approach doesn’t just support your own discipline; it enhances the overall design, strengthening the entire project team and helping prevent misunderstandings that can escalate into disputes.

Contractors
Contractors turn coordinated designs into reality on site, and that’s no small feat. It’s not just about following drawings; it’s about staying on top of all the moving parts, ensuring packages are properly coordinated, and challenging unresolved interfaces or late changes before they become real problems.

The best contractors tie their programme to design maturity and information flow, rather than just pushing ahead for the sake of progress.

It’s also crucial for contractors to understand what design responsibility they assume at handover, whether completing, developing, or verifying it. This means they need to carefully review what has been handed over, identify any gaps or ambiguities, and ensure those are addressed before moving forward. Leading the commissioning process, planning scenario tests, and ensuring clear evidence of acceptance across all parties makes a huge difference.

CRUX data and past disputes have shown consistently that anticipating common pitfalls and addressing them early is what helps keep projects on track, rather than hoping issues will resolve themselves at a later date.

Conclusion

Successful delivery really does come down to recognising and managing interdependence right from the start. That means thinking carefully about how contracts are structured, how project and programme management are organised, and how design processes are structured to foster genuine collaboration. Responsibilities must be clearly defined, and everyone should know who is responsible for closing out which interfaces between packages. When these aspects are addressed early, the team can prevent the kinds of pitfalls that so often escalate into costly disputes. Disputes that drain valuable management time, disrupt business operations, cut into profits, and sap the enjoyment and satisfaction that should come from delivering a successful project. The payoff is a project that not only meets the client’s needs but also stands as a shared success everyone can genuinely be proud of.

Employers/Clients: Are your contract conditions, management structures, and programme gates designed to enable collaboration and close interfaces early, or to push risk downstream?

Designers: Are you engaging other disciplines and specialists early, managing interfaces transparently, and designing to budget and performance so others can rely on your work?

Contractors: Are you proactively coordinating packages, linking programme logic to design maturity, and identifying interface risks before they escalate?

All parties: Are you treating interdependence as a core project value (evidenced in plans, behaviours, and records) or leaving it to chance?

Key Insight	What This Means for Your Project
Interdependence is Essential	The success of every discipline relies on collaboration across all teams.
Multi-Disciplinary Coordination Saves Money	Unclear interfaces and late engagement between disciplines drive costly disputes, delays, and overruns.
Legal expectations are rising	Case law and the Building Safety Act require clear roles, robust documentation, and proactive management of interfaces.
Success is shared	Employers, designers, and contractors each have a unique role in fostering collaboration and managing risk, no one builds alone.
Act Early to Avoid Disputes	Building interdependence into contracts, design processes, and project management from the outset is key to safe, efficient, and dispute-free delivery.

References & Links

• CRUX Insight Eighth Annual Report (2025), From Insight to Foresight (global claims/dispute analysis).
  HKA: https://www.hka.com/news/crux-insight-eighth-annual-report-from-insight-to-foresight/

• Workman Properties Ltd v ADI Building & Refurbishment Ltd [2024] EWHC 2627 (TCC), design completion responsibility under amended JCT DB.
  Atkin Chambers: Case summary and analysis
  DWF: Defining design duties in amended JCT contracts

• BNP Paribas Depositary Services Ltd v Briggs & Forrester Engineering Services Ltd [2024] EWHC 2903 (TCC), full design responsibility including site conditions; wrongful termination.
  DAC Beachcroft: Contractual agreements: It’s the words that count, whether fair or not
  HFW: Scope of works: when does it end? A cautionary tale in knowing your contractual responsibilities

• Building Safety Act 2022, 2024 case developments (incl. BLOs)
  DLA Piper overview: https://www.dlapiper.com/en/insights/publications/2025/01/significant-developments-in-uk-construction-law-in-2024
  White & Case analysis: https://www.whitecase.com/insight-our-thinking/constructing-low-carbon-economy-recent-developments-english-construction-law

About the author

Gerry Brannigan is a Chartered Engineer with over 25 years of experience. Since 2012, he has been appointed as a technical expert witness or expert advisor on more than 50 occasions.

Gerry is an expert witness in building services engineering (MEP) and multi-disciplinary design management, and has acted as the lead expert in complex multi-disciplinary construction disputes. He has given oral evidence at arbitrations, adjudications, and dispute adjudication boards. In addition, he has assisted at mediations and provided a deposition in the USA.

Gerry has opined on liability, design responsibility, client scope, performance issues, risk, professional responsibility, design duties, contractor duties, systems failures and contributed to the assessment of delay factors and events.  Gerry is listed by Lexology as a Thought Leader in Construction and Firm Management, and is Highly Recommended in Lexology’s Arbitration Expert Witnesses guide.

Gerry speaks regularly on the impact of disputes on buildings and construction, with a particular emphasis on design responsibility and implementation of design.

Gerry Brannigan | Forensic Technical Expert | HKA