The off-site edge
Mark Griffin, Growth and Development Director at OSM, an NG Bailey company, discusses how off-site engineering is transforming the delivery of works on live operational sites, improving efficiency, safety and programme certainty.
For engineers and construction professionals, delivering major infrastructure projects in live operational environments is becoming increasingly challenging. As asset owners seek to minimise disruption and reduce carbon emissions, whilst accelerating delivery, contractors are under growing pressure to find smarter ways of working.
Construction in busy, occupied environments such as airports, hospitals, government buildings and logistics hubs presents unique challenges, as they often have restricted access, limited working space and the need to maintain critical operations throughout the delivery phase. In these conditions, traditional on-site fabrication and assembly can increase site congestion, create programme and safety risks, and impact quality consistency, particularly on large-scale building services installations.
Contractors, including us here at OSM, are increasingly turning to modern methods of construction (MMC), including off-site manufacturing, to address these challenges. While often viewed as a new approach, off-site construction has been part of the UK’s built environment for decades, from the prefabricated homes that supported post-war recovery to the system-built developments used to replace ageing Victorian housing stock and drive urban regeneration.
Landmark projects such as the Barbican reflect the longstanding role of industrialised construction in shaping Britain’s cities. What has changed, over the years, is its capability. Today, advances in digital engineering, manufacturing precision and quality control have transformed off-site construction from a practical building technique into a strategic delivery model for major infrastructure projects. By combining the founding principles of prefabrication with modern technology, OSM is helping to improve quality, reduce risk and deliver complex engineering projects more efficiently within live operational environments, including Manchester Airport’s Terminal 2 and Pier 2 upgrades.
Manchester Airport’s £1.3 billion Terminal 2 Transformation Programme (TP2) demonstrates the value of this approach. Delivered within a live airport environment, the programme involved extensive mechanical and electrical infrastructure across a large, multi-level terminal and pier structure, including high-voltage systems, substations, airfield ground lighting, fixed electrical ground power systems and specialist airport technologies.
Critical project milestones
To improve delivery certainty, off-site manufacturing formed a central part of the project strategy, with multi-service modules, valve assemblies and fully serviced vertical risers designed, manufactured and tested in controlled factory environments before installation. In total, 864 off-site solutions were delivered, enabling coordinated sections of infrastructure to be installed efficiently while reducing on-site labour requirements, congestion and programme risk. The approach supported parallel working for trades, improved quality and productivity, and helped maintain critical project milestones.
For the project team, the decision to utilise off-site solutions was driven by the unique challenges of delivering major engineering works within a live airport environment.
By adopting multi-service modules, prefabricated valve assemblies and fully serviced risers, significant volumes of installation, testing and quality assurance could be completed before components arrived on-site. This reduced the number of operatives and trades working simultaneously in constrained areas, minimised disruption to airport operations and provided greater confidence that systems would be installed correctly first time. The approach also contributed to more than 750,000 working hours being completed without a reportable accident.
The approach by OSM also removed 48,000 labour hours from site, significantly reducing the volume of work undertaken within the challenging live environment.
The approach also eliminated 849 site deliveries, helping to reduce congestion around the site and logistical complexity, while cutting project carbon emissions by 289 tonnes, the equivalent of driving around the entire planet 29 times. These efficiencies translated into a nine-month programme saving for a delivery team of 30 people, demonstrating how off-site manufacturing can deliver tangible benefits across productivity, sustainability and project performance, as well as quality and safety.
Digital processes
The benefits of off-site manufacturing extend beyond physical efficiencies. Increasingly, its value lies in the digital processes that underpin delivery. At OSM, technologies such as 4D BIM, digital verification processes and augmented reality (AR) headsets create a connected digital thread between design, manufacture and installation. This enables project teams to visualise sequencing before work begins, validate components before installation and access real-time information in the field, improving coordination and reducing the likelihood of errors and rework. By connecting data across the project lifecycle, digital delivery strengthens decision-making, enhances collaboration and provides greater certainty that what is designed, manufactured and installed aligns with project requirements.
While the benefits of off-site manufacturing are clear, it is not a universal solution or a complete replacement for traditional construction methods. Every project presents its own constraints, and factors such as site conditions, programme requirements, legacy infrastructure and design complexity can make on-site construction the most appropriate approach in some circumstances.
The key is adopting a flexible delivery strategy that applies off-site manufacturing where it delivers the greatest value. For repeatable building services installations, and large-scale projects delivered within live operational environments, off-site methods can significantly improve safety, quality, productivity and certainty. However, the most effective outcomes are often achieved through a balanced combination of off-site and traditional construction techniques.
Greater certainty
As the construction industry faces increasing pressure to deliver projects faster, safer and more sustainably, modern methods of construction will play an increasingly important role in infrastructure delivery. Off-site manufacturing is not simply about moving work from site to factory; it is about creating greater certainty across the entire project lifecycle.
By combining advanced manufacturing techniques with digital engineering, robust quality assurance and collaborative planning, contractors can reduce risk, improve productivity and deliver higher-quality outcomes in some of the industry’s most demanding environments. When applied in the right way, off-site engineering can be a powerful enabler of efficient, predictable and sustainable infrastructure delivery.
