<p>Scaling off, characterized by a binary structure of crusted and loose layers attached to the host soil, is one of the most widespread deterioration types accelerating the extinction of earthen sites. Clarifying its spatio-temporal characteristics is essential to reveal the formation and evolution mechanisms. This study investigated scaling off across three height zones (top, middle, and bottom) and two building orientations (sunward side and nightside) of earthen sites constructed during seven Chinese historical periods in semihumid and semiarid regions of NW China. Field investigation, laboratory measurements, and paleoclimate data analysis were combined to explore its development patterns and influencing factors. Results have shown that scaling off is more severe in the top and bottom zones than in the middle, and more pronounced on the sunward side and under semihumid conditions. Temporally, its development corresponded closely with chronological temperature fluctuations. Moreover, measurements of surface hardness, water, and salt content showed that the deterioration was governed by coupled water-salt migration, thermal variation, and mechanical response. Paleoclimate analysis further suggests that warm periods may enhance scaling off by weakening material mechanical properties and prolonging precipitation duration. The results demonstrate that scaling off is most severe in the top and bottom zones and more pronounced on the sunward side under semihumid conditions, which is mainly associated by the multi-field coupling effects of water, salt, heat, and mechanical processes, providing new insights into the spatio-temporal evolution of scaling off and a scientific basis for targeted protection and reinforcement strategies for earthen sites.</p>