The main goal of this study is to use the factor method to evaluate the service life of ceramic external cladding. An interesting possibility is that a tool may be developed to aid the planning of maintenance operations, to reduce costs, and to ensure a better performance of the cladding system. The method relies on field work data on the state of repair of the façades, based on a survey of 195 façades in the Lisbon area. The factors affecting durability are singled out and quantified through several scenarios with the aim of optimizing the weighting coefficients. The degradation model has provided consistent results for most of the variables influencing the cladding's loss of performance. Adequate knowledge on the durability of a component allows correctly designing the details and planning the maintenance operations that the component requires. These in turn are part of a broader perspective that involves reductions in costs and environmental impact, exactly the challenges that service life prediction proposes to overcome.