Extensive research has focused on numerical methods for analysing regularly stacked masonry, yet the comprehension of load transfer mechanisms in irregular masonry remains lacking [1]. In this context, the present contribution aims to propose a modelling pathway able to extract Representative Volume Elements directly from images of historic masonry, and to determine their failure envelope in the stress space and the corresponding failure mechanisms. To achieve this, recently developed image segmentation tools are combined with distance fields-based morphing procedures and a medial axis extraction technique, effectively lumping mortar joints onto a zero-thickness interfaces geometrical representation [2], which allows for building efficient models. By identifying intersection points between multiple inclusions, the geometry can be further simplified. This geometry representation obtained from real segmented images serves as the main input to a tailored block-based kinematic limit analysis procedure, formulated and solved as a linear programming problem. Morphed blocks are assumed to be infinitely strong and rigid, therefore failure can only occur at the common interfaces between adjacent blocks. Based on these tools, failure envelopes in the homogenised stress space and their corresponding failure mechanisms can be obtained at unparalleled speeds. Simplified geometries yield similar results with enhanced computational efficiency, especially given larger Representative Volume Elements. The procedure will be illustrated on examples of real historic masonry structures. REFERENCES [1] S. Tiberti and G. Milani. 2d pixel homogenised limit analysis for non-periodic masonry walls. Computers & Structures, 218:16–57, 2019 [2] T. J. Massart et al. Level set-based generation of representative volume elements for the damage analysis of irregular masonry. Meccanica, 53:1737–1755, 2018.