Exterior wall painting is one of the most widely-used coating solutions in Portugal. It is particularly susceptible to degradation; this affects the quality of public spaces and the image of cities. The study of service-life prediction contributes to a more rational management of the maintenance of buildings. The state of repair of 220 facades in the Lisbon region of Portugal determined through an in-service survey is analyzed. The model proposed to estimate the service life of painted surfaces is a relatively simple method that balances cost and speed, enabling its practical application to any structure. The models obtained enabled degradation patterns to be identified. The method yielded an average (reference) service life of paint coatings of around 10years. A technoeconomic analysis was then performed that compared various maintenance strategies for a period of time of 20years, as follows: (1)maintenance every 5years, (2)maintenance at 15 and 20years, and (3) maintenance adjusted in accordance with the findings of service-life prediction of painted surfaces. The research reported in this paper proved that technical knowledge can be converted into economic and performance gains. In this case the maintenance strategy based on service-life prediction data proved to be the best. Tools such as these are essential to the maintenance of built heritage.