Abstract This thesis develops a structured, decision-oriented model to improve planning process-es in large building construction projects. The work begins with a literature review of the HOAI 2021, classical and agile project management approaches, decision theory, and Lean Construction principles. The analysis shows that while the HOAI remains an estab-lished regulatory framework, it creates challenges particularly in the early planning phas-es. The HOAI still has a linear logic and limited integration of digital and iterative meth-ods. The planning phases are often characterized by unclear objectives, insufficient needs assessment, fragmented communication, and a lack of structured decision mak-ing. Building on these theoretical insights, an empirical survey was conducted to identify practical challenges and requirements. The survey results confirm the structural deficits identified in the literature and form the basis for developing the model. They highlight the need for clearly defined decision milestones, transparent communication structures, early involvement of key stakeholders, and flexible, iterative planning processes. The resulting model structures decisions independently of the HOAI phases, incorporates controlled iterations, and remains fully compatible with the HOAI. It integrates agile principles, Lean based thinking, and defined roles. Following the development of the model, expert interviews were conducted to validate and refine it. The interviews confirm the model’s fundamental structure while emphasiz-ing the critical importance of early planning phases, the necessity of earlier and clearer decisions, the value of a dedicated moderating role, and the benefits of physical collabo-ration. The feedback led to targeted adjustments of the milestone plan and the decision-making process. The thesis concludes with a reflection on its limitations. Based on these limitations, rec-ommendations are provided for future research and practice, including the modernization of the HOAI, broader empirical studies, and pilot applications of the model. Overall, the results of this thesis demonstrate that a structured, decision-oriented plan-ning model can significantly contribute to modernizing planning processes in the building sector and provides a robust foundation for further research and practical advancement.      «

Abstract This thesis develops a structured, decision-oriented model to improve planning process-es in large building construction projects. The work begins with a literature review of the HOAI 2021, classical and agile project management approaches, decision theory, and Lean Construction principles. The analysis shows that while the HOAI remains an estab-lished regulatory framework, it creates challenges particularly in the early planning phas-es. The HOAI still has a linear logic and limited i...     »