With intense rainfall at times, combined with galloping demographic pressure, Senegalese cities are increasingly exposed to floods. Reducing vulnerability becomes therefore crucial to face up to the consequences of this growing threat. The aim of this article is to demonstrate that the diagnosis of building expresses material vulnerability, a key aspect of population vulnerability. The method consists of establishing, on the basis of a diagnosis, a typology of buildings divided into 5 classes (A to E), which indicates the level of structural vulnerability. The commune of Djiddah Thiaroye Kao on the periphery of Dakar was used as a case study. Our results highlight a variety of situations of vulnerability based on the type of buildings and the socio-economic characteristics of the households. Near 70% of the most vulnerable neighbourhoods are located in the unplanned part of the commune, close to the marshes, and characterised by an absence of urban planning and adequate drainage facilities. The maps produced will be able to help stakeholders and decision-makers to adopt measures appropriate to the local context in order to manage current and future risk areas effectively and sustainably.