A simplified probabilistic methodology is proposed to evaluate excavation-induced damage to adjacent existing buildings from the results of a numerical model of the boundary value problem. To this aim, the probabilities of different damage states are computed as a function of both relevant input parameters, considered as independent random variables, and the relative position between the excavation and the buildings. The proposed approach can be defined as a reliability-based design procedure based on monovariate or multivariate probabilistic analyses, respectively for reinforced concrete and masonry buildings. The procedure is applied to a case-study: the design of an underground station, part of a new subway line in the city of Naples (Italy), for which a large open-pit excavation has been designed.