“…Layered defects are particularly common on building facades, usually occurring at the interface between the finishing layer (such as tiles or decorative paint) and the underlying substrate (such as concrete or brick) (Chew, 1992;Chew and De Silva, 2004;Chew et al, 2005). Since these defects are located below the surface, nondestructive testing (NDT) techniques are required for their detection (Zhao, 2021;Gupta et al, 2022;Shaloo et al, 2022;Silva et al, 2023). Although various NDT techniques, including tapping tests, hammer sound tests, and ground-penetrating radar, have been widely used in the study of facade layering (Deterioration, 2009;Edis et al, 2015;Watase et al, 2015), these methods often require direct contact with the structure, are time-consuming, inefficient in detection, and difficult to combine with automated equipment (such as drones) to alleviate the issues associated with manual testing.…”