Rumah Instan Sederhana Sehat (RISHA) is a concrete prefabrication technology that was originally developed for low-income housing in Indonesia. Its application, which was extended to the Kampung Deret Petogogan flats in Jakarta, shows that RISHA has not been able to facilitate all activities inside. This research aims to identify the optimal span(s) of the struktural modules that must be provided specifically for this case study and assess the suitability of RISHA in facilitating this optimal span(s). Quantitative studies will be carried out in the form of simulations for each spatial dimension in Kampung Deret Petogogan considering several parameters, i.e., spatial organization, spatial relations, and spatial dimension standards. For RISHA to be implemented properly, the spatial planning of Kampung Deret Petogogan needs to be improved as well as the relationships between the spaces, and the standard room size. Furthermore, only three span sizes, i.e., 1.8 m, 2.7 m, and 2.9 m can be accommodated by RISHA at present, while other spans with sizes of 3.3 m and 3.6 m still need to be developed for the benefit of similar projects in the future.