On the horizon are changes to design and build, and possibly the end of later-stage engagement. To understand this design and build dilemma, we need to make clear what we mean by design and build.
Under the design and build procurement route, a single contractor is appointed to take responsibility for both the design and construction of a project. While an initial concept or developed design (often to RIBA Stage 2 or 3) may be prepared by the client’s design team, the contractor typically assumes control of the detailed design through their own consultants and specialist subcontractors.
This is where structural engineers are often introduced or re-engaged at later stages — either novated to the contractor or appointed within the supply chain — to complete detailed calculations, optimise structural systems, or adapt earlier designs to suit buildability and cost constraints.
This later-stage involvement has historically allowed structural engineers to contribute value engineering and innovation; however, it has also meant that key design decisions are sometimes deferred until after procurement, a practice now being challenged by increased regulatory scrutiny.
For decades, the appeal of Design and Build has been clear: speed, efficiency, and above all, cost certainty. In a market where clients are increasingly looking to lower costs, the Design and Build model has naturally risen in preference across the UK construction sector. But a new regulatory reality, driven by the Building Safety Act and the introduction of the “Golden Thread” of information, is beginning to challenge the way Design and Build projects are delivered.
The question now facing the industry is ‘can a procurement model built around cost efficiency adapt to a regulatory framework built around accountability and traceability?’
The Cost-Driven Rise of Design & Build
Clients want buildings delivered faster, with reduced risk exposure and predictable pricing. By appointing a contractor to take responsibility for both design and construction, projects often appear more streamlined and commercially attractive.
In many sectors, Design and Build has become the default procurement route. Consultants frequently produce a Stage 3 design package before a contractor is appointed, after which the contractor’s supply chain completes the design under their control.
From a commercial standpoint, it works. Contractors can innovate, supply chains can optimise systems, and clients can drive competitive pricing. But this method has always relied on a certain degree of design flexibility after the contractor takes control, which is why the Building Safety Act threatens to bring an end to this way of working.
The Golden Thread Changes the Rules
The Building Safety Act contains a new expectation: a fully traceable, accountable and verifiable record of decisions throughout the lifecycle of a building. This ‘Golden Thread’ of information requires that design intent, product specification, compliance decisions and construction details are all documented and maintained. This removes any tolerance for later-stage design changes through value engineering.
Currently, once a project moves into Design and Build, significant parts of the design could be changed to suit the contractor, supply chain relationships, or add-value to the project. Substitutions, value engineering and system redesign are common.
Under the Golden Thread framework, however, every design change must be justified, documented and traceable back to compliance requirements. This increases the administration required and the risk associated with post-Stage 3 alterations.
The golden thread of information means that the earlier design decisions are made and properly recorded, the easier compliance becomes. Late changes will cause compliance issues and possible delays to the project.
The Shrinking Window for Stage 3 Involvement
For structural engineers, like SWJ Consulting, this creates a potential shift for when meaningful project involvement can occur.
Stage 3 has been the key point of engagement: developed design packages are issued, projects are tendered, and consultants often remain involved while contractors develop the technical detail. This is where SWJ can add value to the project with more efficient solutions to the programme and build schedules.
However, if the Golden Thread requires a locked-down final design earlier in the process, clients and project teams may increasingly seek more design information before procurement begins.
The result could be a gradual decline in opportunities to join projects in later stages.
Instead, the industry will see a greater need for early-stage involvement, with structural engineers contributing at concept and developed design stages to ensure compliance strategies are embedded from the outset.
Innovation Will Still Happen — But Differently
This is not to assume that the Building Safety Act will stifle innovation entirely. Construction has always evolved in response to regulation. What is more likely is that innovation will be required earlier in the process.
Rather than redesigning systems during construction, project teams will need to test ideas earlier through coordinated design development, digital modelling and clearer compliance strategies. Supply chains will still bring expertise and product innovation, but within a more structured framework.
SWJ Consulting has always encouraged clients to engage as early as possible to ensure that the best and most efficient solutions are considered, tested and modelled using digital construction technology. Our success in design engineering comes from assessing the realities of a project and not working on worst-case assumptions. This approach doesn’t change whatever stage the project is at when we get involved.
A Procurement Model Under Pressure
The commercial reasons behind the popularity of Design and Build will ensure it does not disappear; however, the procurement model will need to evolve to include greater early collaboration, clearer design responsibility, and stronger information management.
It will be up to clients, contractors, and consultants, like structural and civil engineers, to adapt so Design and Build can support the ‘Golden Thread’ requirements whilst ensuring the innovation and efficiency of the traditional design and build environment is not lost.
A Turning Point for the Industry
The Building Safety Act represents a significant change in UK construction; it is set to reshape how the design team works with contractors, procurement strategies and project timelines.
For SWJ Consulting we have always encouraged early engagement and are ready and willing to work with clients and contractors much earlier in the process. We have the technology to find, test and model the most efficient solutions in the early design stages to negate the need for later-stage value engineering.
Our cooperative approach, clear design leadership with better information management, will ultimately result in a more efficient design and build process that retains the golden thread of information and is more beneficial for clients and contractors alike.
If you have any questions or a project you’d like to discuss with our structural or civil engineering teams, please do get in touch on 01993 225085 (Witney) or 02381 920656 (Southampton) 02381 920656 or email mail@swjconsulting.co.uk.
