In the graduation project of Remmerswaal, N. (2015), a concept for a new building system for the Indonesian kampung was developed: The CAST formwork system. The development of the concept was based on several identified problems of the Indonesian construction sector. The project concluded with a first design of the CAST formwork system, in this project referred to as CAST FS I. Although CAST FS I provided a useful tool to communicate the potential of the CAST formwork system concept, it was only suitable to create small scale prototypes. Due to the limitations of the CAST FS I design, the concept had not been tested on a full scale and therefore no proof had been provided that the concept will actually work. This thesis describes the development of CAST FS II. CAST FS II is a new design of the CAST formwork system that was created to make the development of a full scale prototype possible. The full scale prototype and CAST FS II design were used to test the technical feasibility, ease of use and safety of the CAST formwork system. The design of CAST FS II was created with an iterative design approach. The full scale CAST FS II prototype showed promising results on the levels of technical feasibility and safety. The results of the ease of use testing, however, showed that the design of CAST FS II was still too complex. This thesis concludes with a final redesign of the CAST formwork system: CAST FS III. The design of CAST FS III was based on the test results and focusses on improving ease of use.