Abstract This paper focuses on the experimental and numerical investigation of the size effect and the fracture process on the uniaxial compression strength (UCS) of the banded Alfas porous stone. This natural building material excavated in Rethimnon, Crete, Greece often features two material bands with similar mineralogical properties, but different depositional characteristics and therefore different mechanical parameters. The experimental tests were simulated numerically using the Bonded Particle Model (BPM) available in the PFC2D code. The noticeable unusual increase of UCS with increasing specimen diameter as well as the strong influence of the weaker band on the mechanical behavior of the banded Alfas porous stone are confirmed by the numerical results. Future work will focus on the direct measurement of the weak/strong material band properties and will investigate the effect of the loading rate and boundary conditions on the mechanical response of the BPMs.