The rehabilitation of unoccupied buildings is a major potential path in the production of affordable housing—and an underexplored alternative in Brazil. In turn, assessing design solutions in rehabilitation is a crucial step for appropriate housing policies. This study investigates design patterns in rehabilitated buildings drawing on Christopher Alexander’s “pattern language”, a set of design patterns that would ensure desirable architectural and urban qualities in buildings. First, our approach identifies 76 patterns potentially associated with the rehabilitation of buildings for social housing and establishes them as an analytical and relational framework, meaning that patterns are analyzed not as isolated features but as co-occurring in design solutions, potentially multiplying positive effects over residential use and building performance. Second, it applies the framework to ten rehabilitated buildings in Porto (Portugal) through examining architectural documentation and on-site visits. Third, we identify the frequency and connectivity of patterns based on their co-occurrence in empirical cases through network analysis. Centrality metrics are deployed to interpret the structural relationships of patterns empirically found. Results suggest patterns and relationships potentially responsible for desirable design qualities. This approach is intended to contribute as a tool to assess building design solutions and support evidence-based public policies in social housing.