In France, climate change has intensified heatwaves and summer droughts, significantly affecting the hydromechanical behavior of clayey soils. Variations in soil moisture content induce shrinkage–swelling phenomena that lead to differential foundation settlements, which may cause structural damage and compromise the stability of residential buildings. These buildings are predominantly constructed using masonry, a heterogeneous assemblage of hollow concrete blocks and mortar joints, making such structures particularly sensitive to ground movements. The hollow structure of concrete blocks introduces additional heterogeneity, further increasing the complexity of the global mechanical behavior of masonry. In this context, modeling the mechanical behavior of masonry walls composed of hollow concrete blocks represents a scientific challenge. The present study addresses this issue by adopting the detailed micro-modeling approach proposed by Lourenço. This approach explicitly represents hollow concrete blocks and mortar joints as distinct constituents, incorporating their specific physical and mechanical properties, including different plasticity laws for the blocks and the joints. The detailed modeling of mortar joints provides a more realistic representation of masonry behavior and enables better identification of weak zones prone to crack initiation. All numerical simulations are carried out using COMSOL Multiphysics software. First, a preliminary study is conducted on a detailed model of a hollow concrete block, to assess the validity of the simplifying assumption of modeling the blocks as homogeneous units in the global wall simulation. Then, the investigation focuses on small-scale masonry walls with dimensions of 1.05 × 0.80 m², tested in accordance with NF EN 1052-1 and subjected to vertical and diagonal compression loading. In parallel, laboratory experimental tests are performed to validate the proposed numerical models. Finally, a parametric study is conducted to investigate the influence of mechanical properties of the masonry constituents on the overall structural response.