Abstract:The construction industry uses more resources and produces more waste than any other industrial sector; sustainable development depends on the reduction of both, while providing for a growing global population. The reuse of existing building components could support this goal. However, it is difficult to reclaim components from demolition, and materials remain cheap compared with labour, so new approaches are needed for reuse to be implemented beyond niche projects. This study therefore reviews waste interventions. Multiple case studies, spanning new builds and refurbishment, were undertaken to examine systemic mechanisms that lead to components being discarded. Evidence from fieldwork observations, waste documentation, and interviews indicates that the generators of unwanted components effectively decide their fate, and a failure to identify components in advance, uncertainty over usefulness, the perception of cost and programme risk in reclamation, and the preferential order of the waste hierarchy mean that the decision to discard to waste management goes unchallenged. A triage process is proposed to capture timely information about existing building components to be discarded, make this information visible to a wide community, and determine usefulness by focusing creativity already present in the industry on an exhaustive examination of component reusability and upcyclability.

As-built records for existing buildings tend to be poor. Components that make up the existing building stock must be better characterised to prevent them becoming waste. The first record of materials in an existing building is often the waste report, which classifies materials for waste management and gathers information after the opportunity for higher-value reuse of components has passed. Policy at various levels aims to increase reuse, but an understanding of ‘existing buildings as material banks’ (E-BAMB) is a necessary precursor to overcoming other barriers. This paper reviews the current means of understanding E-BAMB and identifies its shortfalls. This analysis leads to the conception of a strategy in which the various approaches are organised as an information system. The future role of technology and mandatory provision of E-BAMB information at the planning stage are explored. The proposed system would enable specifiers, manufacturers and academics to assess the wealth of materials that can be reused, repurposed or upcycled in new projects or businesses. This does not guarantee that actual reuse will occur, as financial, technical and legal barriers may remain. However, it creates the context for assessing secondary components against their virgin equivalents and the enabling conditions for new circular business models.

The construction industry creates significant volumes of waste timber, much of which has residual quality and value that dissipates in conventional waste management. This research explored the novel concept of reusing secondary timber as feedstock for cross-laminated timber (CLT). If cross-laminated secondary timber (CLST) can replace conventional CLT, structural steel and reinforced concrete in some applications, this constitutes upcycling to displace materials of greater environmental impacts. The fabrication process and mechanical properties of CLST were tested in small-scale laboratory experiments, which showed no significant difference between the compression stiffness and strength of CLST and a control. Finite element modelling suggested that typical minor defects in secondary timber have only a small effect on CLST panel stiffness in compression and bending. Mechanically Jointed Beams Theory calculations to examine the potential impacts of secondary timber ageing on CLST panels found that this has little effect on compression stiffness if only the crosswise lamellae are replaced. Since use of secondary timber to make CLST has a more significant effect on bending stiffness, effective combinations of primary and secondary timber and their appropriate structural applications are proposed. The article concludes with open research questions to advance this concept towards commercial application.

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The construction industry creates significant volumes of waste timber, much of which has residual quality and value that dissipates in conventional waste management. This research explored the novel concept of reusing secondary timber as feedstock for 'cross-laminated secondary timber' (CLST) through a review of the literature. If CLST can replace conventional cross-laminated timber (CLT), structural steel and reinforced concrete in some applications, this constitutes upcycling to displace materials with greater environmental impacts. The paper introduces the rationale for such an intervention and assesses its feasibility. It concludes with open research questions to advance the concept towards commercial application.