This paper is addressed to construction professionals, engineers and architects entrusted to assess the seismic vulnerability level of historical and architectural heritage buildings and to ensure their safety. Masonry building collapses caused by seismic events highlight frequent cases of loss of equilibrium, that is, the rigid overturning of structural portions. The study of collapse mechanisms can be effectively performed using the kinematic analysis methods, recently adopted by the Italian Building Code. Referring to a particular structural element (the masonry arch), a typical component of historic buildings, this paper proposes an original approach to perform seismic verification based on an algorithm devoted to this topic. Thanks to this algorithm, the a-priori choice of failure interfaces is avoided, as it is possible to individualize the kinematism and its related collapse load factor. The seismic verification which follows is performed according to the Italian Building Code.