Decision support framework for designing out waste implementation in the wall system of residential projects: a New Zealand case study

Purpose Designing out waste (DoW) is recognised as an effective strategy for minimising construction and demolition waste (CDW) at the design stage. However, existing DoW guidance remains largely generic and provides limited support for identifying, evaluating, and selecting suitable DoW alternatives in practice. As wall elements are a major source of waste in residential construction, this study develops a decision support framework for implementing DoW in the wall system of residential projects in New Zealand. Design/methodology/approach A mixed-methods research design was adopted, comprising three phases: conceptual framework development, framework development, and framework evaluation. Exploratory studies and a systematic literature review informed the conceptual framework. Desktop analysis and expert interviews were then undertaken to develop the framework. A hybrid fuzzy analytic hierarchy process (FAHP) and fuzzy technique for order preference by similarity to ideal solution (fuzzy-TOPSIS) was applied to evaluate and rank DoW alternatives against multiple sustainability criteria. The framework was subsequently evaluated and refined through a focus group with industry experts. Findings The framework provides a structured process for supporting DoW implementation from the design stage by identifying applicable DoW alternatives, integrating project-specific implementation factors, and evaluating alternatives against economic, environmental, and social sustainability criteria. Research limitations/implications The framework was developed for timber-framed residential wall systems in the NZ context and assessed through a simulation-based feasibility demonstration and preliminary expert evaluation. Future research should examine its application in live projects and its transferability to other building elements and construction contexts. Practical implications The framework provides project stakeholders with a structured process for identifying, evaluating, and selecting suitable DoW alternatives, taking into account sustainability criteria, stakeholder preferences, and project-specific implementation conditions. Originality/value This study advances DoW research by moving beyond generic design guidance to a practical decision support framework that integrates all five DoW principles within a multi-criteria decision making process. The study also demonstrates the application and integration of a hybrid FAHP-fuzzy TOPSIS approach to support design-stage waste prevention, making both theoretical and practical contributions to CDW minimisation and sustainable construction.