Unlocking the full potential of retrofit: An engineer's perspective
Key takeaways
With the right mindset retrofit can become a catalyst for innovation, carbon reduction and long-term value. But this shift will require decisive action.
Smart technologies increasingly allow for more accurate evaluation and detailed assessment of a building’s capabilities.
The build strategy must be a key design driver from the start of the project. This requires early engagement between the design engineers, contractors and specialist supply chain.
In recent years, a "retrofit-first" approach has gained significant momentum in the UK, driven in part by the urgent need for carbon reduction and new legislation.
In 2024, the Deloitte Crane Survey revealed that London saw an equal number of retrofit and new build projects.
Policies such as the Minimum Energy Efficiency Standards (MEES) are encouraging retrofits, while buildings with low Energy Performance Certificate (EPC) ratings face restrictions on new tenancies, pushing developers to upgrade older assets or risk becoming noncompliant.
However, designers, contractors and developers often leave opportunities untapped, not fully realising the potential in retrofit projects.
Martin Feakes, Head of Engineering at Mace, argues that the construction industry is too often constrained by traditional thinking, missing opportunities to redefine what’s possible through engineering-led innovation.
- From obstacle to opportunity: Maximising the potential of existing structures
The construction industry often assesses buildings with a mindset focused on limitations, rather than potential. This risk-averse approach can lead to conservative designs or premature demolition, decisions that carry financial and carbon costs.
Smart technologies increasingly allow for more accurate evaluation and detailed assessment of a building’s capabilities. For example, at EDGE London Bridge, Mace is trialling sensors embedded in foundations to measure structural loads in use, enabling efficient, carbon-saving designs in the future. High-resolution laser scanning technologies can create detailed 3D models of structures, allowing more accurate assessments.
Additionally, by calculating utilisation ratios for each structural element, engineers can give project teams the confidence to retain rather than replace structural components, avoiding unnecessary reinforcements or replacements.
- Building certainty: Understanding the unknown factors
Existing buildings pose numerous challenges, including missing as-built documentation, difficulties in testing and inspecting legacy materials, and reliance outdated design codes. These factors introduce uncertainty around structural integrity, often resulting in overly conservative design responses that limit reuse opportunities.
Addressing this challenge requires a shift to a “prove, not presume” culture. Rigorous testing programmes should begin early in the design phase, using tools such as ground-penetrating radar, core sampling, and non-destructive ultrasonic testing to validate assumptions and reduce risk.
Additionally, integrating structural health monitoring from the outset can inform long-term asset management strategies, helping project teams make data-driven decisions.
- Standardising proving and warranting structures
Inconsistent approaches to proving and warranting existing structural elements often cause delay and lead to unnecessary complications, particularly when different regulations or codes are applied.
By establishing common guidelines and certification, validation processes can be streamlined, reducing delays and driving a common understanding of how to gain confidence in reused structural elements.
This approach would improve certainty for developers and contractors and simplify how existing structures are warranted.
- Lead with the build strategy
The design approach of a retrofit project has a disproportionate impact on the construction methodology when compared to a new build. This can result in inefficient use of resources, higher costs, longer programmes and increased carbon emissions during the construction phase.
The build strategy must be a key design driver from the start of the project. This requires early engagement between the design engineers, contractors, and specialist supply chain. By collaborating early on, the team can identify more efficient construction approaches, streamline processes, and ensure that temporary works are simplified to become permanent solutions or omitted entirely.
- Bridging the knowledge gap
Upskilling the next generation is essential to ensure we don't just preserve the past but build on it. The current generation of designers and engineers has typically been trained in the design of new build steel and concrete frames, which are based on well-understood load paths. However older buildings often use construction methods and materials that are unfamiliar to younger engineers. This creates a significant knowledge gap when it comes to retrofitting older structures.
Education and professional development programmes must promote upskilling in retrofitting ageing assets. This ensures that the next generation of engineers are equipped with the right skills to solve the unique challenges posed by older buildings. Additionally, experienced professionals with a deep understanding of older structures should be better integrated into the design process, helping to bridge the knowledge gap.
- Retrofit a catalyst for innovation
With the right mindset retrofit can become a catalyst for innovation, carbon reduction, and long-term value. But this shift will require decisive action.
Developers must invest earlier in rigorous building assessment and briefs that prioritise re-use. Engineers need to lead boldly by bringing forward solutions based on what buildings can do. Industry bodies should accelerate the development of standardised reuse assessment frameworks and guidance.
Only by moving retrofit from possibility to priority can we reshape the built environment to meet the demands of a net zero future.
