<p>Understanding the degradation of cement-based tile adhesive mortars under weather conditions is essential for improving facade tiling systems, especially in the context of increasing climate variability. However, owing to the inherently complex microstructure and properties of these cement adhesives, capturing their degradation mechanisms within tiled systems has proven challenging. Here, we employed confocal fluorescence microscopy in conjunction with mechanical testing and analytical characterization techniques (SEM/EDS, TGA, FTIR) to obtain a microscale-level understanding of the weathering-induced deterioration process of cement adhesives in tiling systems. Under prolonged exposure to an accelerated weathering regime, we identified a three-stage degradation pathway: (1) initial wetting and a rapid decline in adhesion performance; (2) onset of micro-cracking at the adhesive–tile interface, facilitated by voids entrained beneath the tile surface; and (3) progressive widening of interfacial cracks, accompanied by the formation of disjointing cracks, leading to near-complete adhesion loss. Key factors contributing to these degradation stages were identified, including phase transformations, the distribution of micro-pores and voids, and loss of polymeric phase at the tile interface. Based on these findings, we proposed a microstructure–property model that elucidates the weathering behaviour of tiling systems and offers a foundation for developing strategies to enhance their long-term durability—towards safer and more resilient building façades.</p>