Social Housing is increasingly a focus of debate in many countries because of the escalating need for affordable housing that has become intertwined with the needs of society both emergent and traditional. The delivery of social housing, however, is often complex from the many stakeholders involved resulting in design challenges on account of conflicting needs. This paper presents a conceptual model for Design Decision Support in the face of emergent needs from multi-use scenarios defined by the multiple stakeholders. The Brazilian government’s Minha Casa Minha Vida social housing program is the basis for the framework’s conceptualization. The model allows for analysis of emergent user and design needs during design using probabilistic Hidden Markov Modeling of requirements changes. This paper’s novel contribution is to present a theoretical conception of HMM in the analysis of changes in social housing requirements and modeling their interdependencies in front-end design decision making. The paper, therefore, adds to knowledge of requirements forecasting in design of social housing in the face of emergent needs.