Across London, the reuse of existing buildings has become the defining trend of the construction market. From commercial retrofits in the City to residential conversions across inner boroughs, developers, planners and designers are increasingly favouring retention over demolition. Sustainability targets, planning policy, embodied carbon reduction and economic pressure have combined to make refurbishment and structural reuse the default approach rather than the exception.
Yet beneath this progressive narrative lies a growing and uncomfortable truth. Structural reuse, particularly in complex cut-and-carve projects, is not a low-risk alternative to new build. In many cases, it is a higher-risk activity that the industry continues to treat as routine.
Reuse Begins with Uncertainty, Not Certainty
Unlike new construction, reuse projects begin with unknowns that cannot be fully resolved through drawings or desk studies. Existing buildings often contain hidden defects, undocumented alterations, historic construction practices and degraded materials that remain concealed within retained structures.
Load paths that once made sense are altered, redundancy is reduced and tolerances tighten. What was once an over-engineered frame can quickly become marginal once floors are removed, openings enlarged, plant loads increased or building use changed.
The Construction Phase Is Where Risk Peaks
These risks are most acute not in the completed building, but during the construction phase itself. Temporary works, partial demolition, propping and sequencing represent the point of maximum structural vulnerability.
Industry data and historic failures consistently show that structural incidents are far more likely to occur during alteration and demolition than in completed structures. For workers on site, cut-and-carve environments introduce elevated risks: unstable floors, unpredictable connections, progressive collapse mechanisms and constrained access all combine to make these projects inherently more dangerous than greenfield construction.
Commercial Pressure Is Undermining Due Diligence
Despite these realities, refurbishment schemes are frequently programme-driven and commercially compressed. Intrusive surveys are value-engineered, conservative assumptions are resisted, and temporary works are treated as a cost rather than a safety-critical system.
This approach is increasingly incompatible with the regulatory and liability environment now governing UK construction.
The Building Safety Act Raises the Bar for Reuse
The introduction of the Building Safety Act has fundamentally changed long-term accountability across the industry, particularly for higher-risk buildings. The requirement to maintain a continuous and accurate Golden Thread of information is especially challenging in reuse projects, where historic records are often incomplete or unreliable.
Demonstrating competence, compliance and structural safety in buildings that pre-date modern design standards represents a significantly higher bar than in new build. The consequences of failure now extend far beyond practical completion and into the long-term operational life of the asset.
Material Choices Add Further Complexity
Material selection within reuse projects introduces additional layers of risk. The growing enthusiasm for timber floors and lightweight structural systems is frequently driven by embodied carbon targets and cost efficiency.
While modern engineered timber products can demonstrate predictable structural and fire performance when correctly detailed, their behaviour within retrofit environments demands caution. Many existing buildings were never designed to accommodate timber fire strategies, and introducing combustible materials into legacy structures can place disproportionate reliance on encapsulation, sprinklers and long-term management regimes that may degrade over time.
Moisture and Durability Are Often Underestimated
Water ingress represents another long-term risk that is frequently underestimated in reuse projects. Timber systems are inherently sensitive to moisture, particularly during construction phases when buildings are exposed and weather protection is imperfect.
Once compromised, timber elements can deteriorate rapidly, leading to loss of structural integrity, serviceability issues, mould growth and costly remediation. Concrete slabs, while carbon-intensive, offer durability, fire resistance, acoustic mass and resilience to water exposure that have been proven over decades of service.
Sustainability Requires Honest Whole-Life Assessment
The debate should not be framed as timber versus concrete, or reuse versus new build. It is fundamentally a question of proportional risk, long-term performance and honest whole-life assessment.
Whole Life Carbon calculations must account not only for upfront embodied emissions, but also for durability, adaptability, maintenance and the likelihood of early replacement. Structures that require significant intervention after a short service life may ultimately undermine the sustainability objectives they were intended to support.
Insurance Markets Are Already Responding
Insurance markets are beginning to reflect these realities. Professional indemnity cover for complex structural reuse and mass timber projects is becoming harder to secure, more expensive and more restrictive in scope.
This is not a theoretical concern. It is a commercial signal that systemic risk is being reassessed. As insurers retreat, liability concentrates on fewer parties, raising fundamental questions about who ultimately carries responsibility when long-term performance falls short of expectations.
Reuse Will Remain Essential, but It Must Be Done Properly
London’s retrofit-first planning framework is unlikely to reverse — nor should it. The environmental cost of wholesale demolition and reconstruction is undeniable, and structural reuse will remain essential to achieving net-zero ambitions.
However, sustainability cannot be reduced to carbon metrics alone. Structural safety, fire resilience, insurability, worker protection and long-term adaptability must carry equal weight.
Structural Reuse Demands Discipline, Not Assumption
Structural reuse is not refurbishment in the traditional sense. It is a form of structural engineering that demands enhanced investigation, conservative design, robust temporary works and realistic programming.
It requires clients willing to invest in due diligence, designers prepared to challenge optimistic assumptions, and contractors empowered to prioritise safety over speed.
The risk lies not in reuse itself, but in the assumption that reuse is simple. London’s existing buildings can and should be adapted — but only with the humility to acknowledge their limits and the discipline to manage the long-term consequences. Without this, today’s sustainability solutions risk becoming tomorrow’s technical, regulatory and commercial liabilities.
