PERI UK has revealed the engineering behind one of the Hinkley Point C project’s most demanding phases: the formation of the geometrically complex reactor domes. Faced with the challenge of pouring concrete for structures that curve in multiple directions – without the ability to use traditional through-ties – PERI UK engineers
Hertfordshire sits at the centre of some of the most active residential and commercial development in the South East. With housing targets rising and the AMP8 investment cycle bringing billions into water infrastructure over the next five years, demand for reliable water utility contractors across the county has never been
PERI UK has revealed the engineering behind one of the Hinkley Point C project’s most demanding phases: the formation of the geometrically complex reactor domes. Faced with the challenge of pouring concrete for structures that curve in multiple directions – without the ability to use traditional through-ties – PERI UK engineers developed a bespoke, non-standard solution. The system allowed for the successful completion of the Unit 1 inner dome in late 2025 and has significantly accelerated works on the Unit 2 outer dome, where the entire platform solution was installed in under 14 days. “Because of this project’s uniqueness, the design solution had to be created from scratch,” explains Gabriel Constantin, major projects lead at PERI UK Infrastructure. “From the onset and throughout the development of the solution, we calculated where the challenges may arise later. These initial stages were marked by, and successful because of, close collaboration and support which continued throughout implementation.” Curves in multiple directions PERI UK VARIO formwork was selected for its adaptability, with 199 bespoke panels fabricated specifically for the dome works. Earlier transition sections from the vertical reactor walls up to level 13 incorporated RUNDFLEX circular wall formwork panels before progressing fully into the dome curvature. Building without ties The challenge extended well beyond geometry. The formwork had to operate approximately 45 m above ground level and support significant construction loads without relying on conventional tie systems. The reactor structure did not allow implementation of traditional through-ties, due to the interior airtight 6mm steel shell. To overcome this, PERI UK engineers developed, from scratch, a unique, non-standard solution that combined several systems. The design incorporated SCS Starter Brace with 550 Strongbacks and load-bearing SB platforms suspended horizontally around the perimeter of the reactor building combined with a single special component – 45-degree anchor adapters – for transferring the concrete loads back into the structure in the absence of ties. While SB platforms are typically used vertically for single-sided wall construction, at Hinkley Point C they were reconfigured to create platforms approximately 5 m wide to facilitate the curved concrete pour, around 5 m in height, with the special design of the platforms able to support the complex formwork, fresh concrete pressure, and heavy equipment and live loads of the operatives on site. Designing the solution digitally From an engineering perspective, the design required extensive modelling. Initial proposals began as 2D engineering drawings before progressing into 3D CAD and digital models to better visualise the interaction between the formwork, platforms, reinforcement, and surrounding structures. In addition, the PERI digital system was able to quickly produce kit lists for procurement on site. Because the configuration fell outside standard system parameters, the PERI UK engineering team developed a full structural model to verify loads, connections, and anchor forces. Load paths were carefully designed so that forces transferred through steel RCS rails rather than through the timber deck, ensuring the system could safely resist the pressure of large concrete pours. Learning, adapting, and accelerating The dense reinforcement within the reactor walls presented further constraints. Anchor positions had to be carefully coordinated around tightly spaced rebar grids and embedded components. During construction, slight deviations in anchor positioning required sections of the system to be redesigned on site. To avoid any issues when the formwork installation was mirrored on the reactor dome for Unit 2, the PERI UK engineering team supported the site team with precise anchor placement and simplifying platform installation. “PERI’s digital engineering approach not only played a key role in planning and risk reduction, particularly through rapid generation of procurement-ready kit lists, but it enabled the effective transfer of lessons learned from Unit 1 to Unit 2, directly supporting our target of achieving a 20% improvement in both time and cost,” explains a project engineer involved in the delivery of the reactor building. Prefabrication also played a key role in efficiencies and speed of the installation. Many elements were assembled before delivery, reducing work at height and allowing platforms to be installed rapidly once on site. Throughout the project, close collaboration between PERI UK engineers and the construction team at Hinkley Point C ensured challenges could be addressed quickly. “We believe early involvement of the supply chain will be vital in meeting future UK energy and infrastructure demands,” says the project engineer. “Refining and building on proven methods from the outset, projects can achieve substantial improvements in both cost efficiency and delivery timelines. “Working alongside a highly experienced reactor construction team, PERI UK’s solutions are a clear benchmark. It makes complete sense to integrate these systems into future nuclear projects from the earliest planning stages.” The result has seen unique formwork solution that demonstrates the adaptability of PERI UK systems when applied through detailed engineering and strong project integration, on a scheme that is critical to the UK’s future infrastructure. 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Hertfordshire sits at the centre of some of the most active residential and commercial development in the South East. With housing targets rising and the AMP8 investment cycle bringing billions into water infrastructure over the next five years, demand for reliable water utility contractors across the county has never been higher. Whether you are a developer appointing a self-lay provider for a new build scheme, a Tier 1 contractor sourcing a subcontractor for mains laying, or a water company looking for framework partners, choosing the right contractor matters. Accreditations such as WIRS (the Water Industry Registration Scheme, operated by LRQA on behalf of all UK water companies) are essential for any contractor installing water mains and services. Beyond that, factors like geographic coverage, breadth of services, and track record on similar projects all play a role. The following contractors are among the most established and capable water utility specialists operating in Hertfordshire. McFadden Utilities McFadden Utilities is a family-run water utility and civil engineering contractor based in Welwyn Garden City, Hertfordshire. Established in the early 1980s, the company has been operating in the water infrastructure sector for over 40 years, making it one of the longest-standing utility contractors in the county. McFadden holds WIRS accreditation for self-lay water services, covering both onsite and offsite installations. The company is also WIAPS accredited (Water Industry Approved Plumbers Scheme) and carries ISO triple certification across quality (ISO 9001), environmental (ISO 14001), and occupational health and safety (ISO 45001). Additional credentials include Constructionline Gold and Achilles UVDB Audited status. The company’s service range is broader than most water-only specialists. Alongside self-lay and main laying, McFadden covers reinstatement works, tarmac and road surfacing, new water connections, leak detection and repair, metering, and under-pressure drilling. This end to end capability means developers and main contractors can work with a single provider from excavation through to final reinstatement, rather than coordinating multiple trades. McFadden operates across Hertfordshire, London, and the wider South East, working with clients including Affinity Water, Thames Water, and Tier 1 contractors such as Balfour Beatty and Skanska. The company has also delivered infrastructure work on HS2. SB Civil Engineering SB Civil Engineering is based in Hatfield Broad Oak, Hertfordshire, and has been operating as a regional civil engineering contractor since 2005. The company holds Thames Water Tier One health and safety approved contractor status and is also an Anglian Water approved contractor, giving them direct approval to carry out sewer connections and diversions across both water company regions. SB Civils’ core strengths sit in Section 278 highways works, specialist drainage, sewer connections, and groundworks. They work across the education, rail, residential, and commercial sectors, and have built a reputation in particular for deep open-cut excavation, over-pumping, and confined space entry work. Their ISO 14001 environmental certification reflects a structured approach to environmental management on site. A T Bone & Sons A T Bone & Sons is a family-run civil engineering and land services company based in Hertfordshire. Founded in 1957, the company has nearly 70 years of experience across the county, making it one of the longest-established contractors in the region. ATB originally grew out of the arable farming industry, gradually expanding into civil engineering, groundworks, and drainage through word of mouth and repeat business. Today the company serves private and commercial clients across Hertfordshire, Bedfordshire, Buckinghamshire, and Greater London. Their civil engineering capabilities include groundworks and earthmoving, drainage installation, hard and soft landscaping, and commercial steel buildings. The breadth of their offering and their deep roots in the Hertfordshire business community have made them a trusted name for developers and landowners who need infrastructure work delivered by a contractor that knows the local landscape. LPC Construction LPC Construction is a multi-utility civil engineering contractor based in Watford, Hertfordshire. Founded in 1997, the company has over 25 years of experience delivering utility infrastructure projects ranging from small residential connections to multi-million-pound contracts. LPC holds NERS accreditation and works regularly with UK Power Networks and major independent connection providers. Their capabilities span trenching, cable installation, multi-utility coordination, EV charger infrastructure, and street lighting. While their primary strength is in electrical infrastructure, their multi-utility offering includes water and communications ducting, making them a viable option for developers looking to bundle services. North Herts Utility Contractors (NHU) NHU is a multi-utility civil engineering company based in Hertfordshire with over 25 years of experience supporting national infrastructure projects. The company specialises in surfacing, excavation, and utility installations, primarily within the technology and telecoms sectors. NHU’s long track record in Hertfordshire and their experience with large-scale infrastructure projects make them a known name in the county’s utility contracting landscape. Their combination of civil engineering capability and utility installation experience positions them well for projects that require both disciplines. What to Look for in a Water Utility Contractor If you are appointing a water utility contractor in Hertfordshire, there are a few things worth checking before you commit. WIRS accreditation is the baseline requirement for any contractor installing water mains and services. It confirms that the company has been technically assessed by LRQA and meets the standards required by all UK water companies. You can verify a contractor’s WIRS status through the LRQA directory. Beyond accreditation, look at the breadth of services on offer. A contractor that can handle reinstatement and surfacing as well as pipe installation reduces the number of parties involved and keeps the programme tighter. Ask about their experience in your specific water company region, as each water company has its own policies and adoption requirements. Ofwat’s guidance on self-lay is a useful starting point for understanding how the competitive water connections market works. Finally, check their insurance levels and whether they hold any additional credentials such as ISO certification or Constructionline membership, both of which indicate a mature approach to quality and safety management.