<p>Fire exposure followed by water extinguishing severely compromises the structural integrity of granitic building stones, yet the underlying thermo-mechanical mechanisms remain inadequately understood due to experimental challenges in replicating realistic thermal gradients and fracture evolution. This study overcomes these limitations by combining high-speed induction heating experiments with grain-based numerical simulations to investigate the superposition effects of realistic fire-induced temperatures followed by either rapid water cooling or gradual air cooling on crack development and residual mechanical properties in granite. Using an integrated approach, we demonstrate that rapid heating induces fewer, larger thermal cracks, partially preserving peak strength despite internal damage, while rising temperature progressively reduces strength and stiffness through pervasive micro-damage, highlighting the importance of thermal history. Crucially, the cooling method governs post-fire integrity. Natural air cooling facilitates partial recovery of strength and stiffness while limiting macro-crack development. Conversely, rapid water quenching superimposes intense thermal shock, significantly exacerbating damage: it elevates crack density and propagation, increases deformation, and causes severe mechanical degradation compared to air cooling. These results provide clear evidence that the choice of extinguishing strategy critically determines residual performance, with water cooling causing profoundly worse structural degradation. Consequently, the cooling phase is as critical as the heating exposure in determining final damage. These findings necessitate considering both realistic thermal loading profiles and cooling strategies in post-fire structural evaluations, safety assessments, and conservation of granite masonry, especially for heritage structures.</p>