## 5 Conclusions  
This study provides a comprehensive examination of the factors influencing the adoption of CE principles within the building sector, drawing on both quantitative and qualitative insights from 10 sustainability experts. By assessing the importance and feasibility of 15 CE strategies, evaluating their applicability to diverse building types, exploring role of multiple project lifecycle stages on effective implementation, and identifying the stakeholders most capable of driving CE adoption. This is performed by addressing four research questions: (1) Which CE strategies are most feasible and impactful for the wider adoption of circular practices in the building sector? (2) How does the type of building influence the feasibility of adopting CE strategies? (3) What roles do different stages of a building's project lifecycle play in the effective implementation of CE strategies? (4) How do various stakeholders influence the adoption of CE strategies in the building sector? In this investigation, we identified and evaluated 15 CE strategic actions throughout the entire building lifecycle, encompassing design, procurement and construction, operation and maintenance, and ultimately the end-of-life phase. The results reveal that, among these, renewable energy integration, design for durability and longevity, and prefabrication and offsite construction stand out as the most feasible options. Their strong alignment between perceived importance and practical applicability underscores their potential to be readily implemented within the building sector. Conversely, procuring reused/recycled and bio-based materials and facilitating building deconstruction at the end of life, were acknowledged as critical for advancing circularity, however exposed to more significant feasibility hurdles. Furthermore, this study indicates that building type and project phase critically influence CE feasibility. Storage and industrial buildings emerged as especially conducive environments for adopting CE principles, likely due to their simpler designs and flexible layouts. They can serve as pilot projects for CE adoption, given their high feasibility scores. Lessons learned from these projects can inform broader implementation across other building types. In contrast, residential and healthcare facilities, with their stringent requirements and stakeholder preferences, present more formidable hurdles. Through examination of the building lifecycle stages, we noted the varying levels of potential for integrating CE principles across different phases. Key findings reveal that the briefing and design stages hold the greatest potential for incorporating CE practices. These early stages are pivotal for defining the project's vision, strategy, and sustainability goals, allowing stakeholders to embed circularity principles effectively. Decisions made during these stages, such as material selection and construction methods, have long-lasting implications for the entire building lifecycle. The results obtained underscore the critical role of stakeholder collaboration throughout the lifecycle. Owners and designers are identified as key drivers during the initial stages, shaping the project's CE framework. Owners, as the primary decision-makers that set the project's direction and influencing the project stakeholders to align with CE goals. Designers influence the integration of CE principles through material selection, architectural choices, and shape the owner's brief into actionable design solutions. Moreover, designers and consultants have a crucial role in ensuring that materials and components are selected for their recyclability, reusability, and longevity, contributing to a circular framework that enhances resource efficiency and reduces waste. While the findings are broadly applicable, the regional focus limits their direct generalizability to contexts with different economic conditions, cultural attitudes, and environmental priorities.