Conversion projects are considered as a growing market within the new build and in particular the repair market within the maritime industry, due to ever more demanding environmental regulations. A development that Royal Niestern Sander (KNS) embraces and wants to exploit further. Although conversion projects are already being executed, currently the thought prevails that ‘project efficiency could and should increase’. The purpose of this research is to provide an approach that equips KNS establishing a best fit project organisation for in particular large, unique conversion projects to define, plan and execute these projects as efficient and effective as possible, as this combines both repair yard and new building characteristics. Both individual organisations were analysed through the lenses of The Delft Systems Approach (DSA), to identify the current ‘as-is’ status. Subsequently, the processes and function responsibilities of key-players of both organisations were assessed and compared. The root-causes for fundamental differences between organisational approaches were identified and proved to be project size, the degree of uncertainty and as a consequence of aforementioned causes, the contract form. Literature was consulted to explore already existing solutions regarding these aspects and to provide a wider, theoretical background in mainly organisation forms and the concept of maturity models. The retrieved insight in the individual and comparative analysis in combination with the literature review provided a foundation for the establishment of an ideal framework, thereby integrating the new build and repair organisations in order to cope with large conversion projects, while simultaneously optimising the individual organisations. As input for the defined framework, scenarios were specified and correlated with actual performed projects that served as validation for the ideal framework. The case studies captured the complete range of projects, varying from small straightforward repair projects, to large new build projects and conversion projects in between. From these case studies, organisation proposals for the respective projects, large conversion projects in particular, were distilled; comprising a structured implementation strategy that is to be executed during the order development phase (where project definition takes place). To conclude, a roadmap for the near future is proposed containing the required steps to undertake for achieving operational excellence.