The paper presents numerical simulations conducted on a masonry church located in the city of Gerace, in southern Italy. The typical construction technique of the region involves irregular masonry of calcarenite stones. The region is characterized as a very high seismic zone and has experienced severe earthquakes in the past. Therefore, it is deemed relevant to investigate and propose efficient retrofitting techniques for this structural typology. In this research work, an innovative Iterative Finite Element Upper Bound limit analysis code was implemented. This code is capable of investigating any irregular and complex structure discretized with hexahedron elements. The hexahedron elements are connected by interfaces exhibiting rigid plastic behavior, enabling simulation of sliding and rotation between them. The code accounts for a no-tension material, mimicking the behavior of existing and deteriorated masonry. The simulations have revealed a high seismic vulnerability, with automated failure patterns consistent with typical patterns observed in past seismic events. Additionally, risk mitigation is investigated through the installation of tie-rods at the top of the church, aimed at improving interlocking between orthogonal walls. This study validates the efficiency and accuracy of the proposed numerical approach. The results emphasize the effectiveness of tie-rod installation in reducing expected seismic risk.