The natural risks of flooding inherent to Mediterranean climates is a well-known fact, but one difficult to gauge and rarely accurately in terms of space, quantity and degree. Fortunately, in Spain the national Cartographic System for Flood Areas (SNCZI) partially compensates for the deficit, calculating the probability of these natural phenomena. The present paper describes the number, location and characteristics of the homes exposed to flooding in Extremadura. The methodology used in the study reveals in great detail the clandestine homes built on land not apt for urban development (via scans and visual detection techniques using the available series of ortho-rectified aerial photographs), particularly those at flood risk (determined by SNCZI cartography). This reveals deficiencies in risk management and land use. Also, the information leads to the conclusion that current action from the Administration is ineffective in preventing any risk of flooding, and that the risk is known, but ignored.