This study examines the structural performance of an over-a-century-old unreinforced brick masonry wall with a cellular design, located behind the center hall of the Senate Hall building. The wall's condition was assessed through a visual inspection survey, revealing significant cracks and deterioration on the exposed, unplastered exterior, while the plastered interior exhibited only minor cracks. Non-destructive tests (NDTs), including the rebound hammer and ultrasonic pulse velocity, were conducted to determine mechanical properties at various locations. Two 3D finite element models were developed: one incorporating mechanical properties for nine distinct segments and another using overall average properties with macro-homogeneous brick and stone components. Using actual test-based properties, load calculations were performed following IS:875 Part 1:1987, with static analysis considering the self-weight. Results indicate that the model utilized experimental mechanical properties (EMP) instead of average mechanical properties (AMP). Comparing the AMP model to the EMP model, the study observed that the masonry wall's stress response increased by 31%, and its deformation response increased by 5%. The segmented model provides an accurate assessment of stress distribution, as its properties are region-specific and closely resemble the actual scenario, making it useful for strengthening and retrofitting strategies. The findings highlight the necessity of detailed property differentiation to effectively address structural vulnerabilities identified during visual inspections.