<![CDATA[The deterioration of wall surfaces resulting from fungal proliferation in tropical heritage houses is governed by interconnected moisture-transfer processes operating within and around the building envelope. Consequently, engineering-based interventions are required to address persistent humidity-related problems. This study seeks to develop alternative strategies for reducing wall moisture by examining soil geology, drainage performance, and hygrothermal characteristics as interconnected determinants of building deterioration. The research was conducted in Karangturi, Lasem, an area characterized by a humid tropical coastal environment and a substantial concentration of heritage buildings. A mixed-methods research design was adopted, incorporating variables including soil texture and permeability, drainage conditions, air temperature, relative humidity, illuminance, air velocity, and wall-surface moisture. The findings demonstrate an association between soil characteristics and the occurrence of rising damp. Wall-surface moisture exhibited a pronounced asymmetrical distribution, suggesting vapor accumulation associated with insufficient air movement and localized air stagnation. These environmental conditions support the development of a moisture-vapor accumulation mechanism within the interior environment. The findings establish a diagnostic sequence in which fine-grained soils are associated with capillary moisture rise, subsequently contributing to an increased indoor vapor load. When this condition occurs simultaneously with stagnant airflow and relative humidity levels exceeding 80%, the potential for fungal proliferation increases substantially. An integrated, field-verifiable mitigation strategy can be implemented through adjustments to subsurface drainage, installation of capillary breaks, application of vapor-permeable lime plasters, and improvement of natural ventilation. The range of mechanisms identified through this study can provide a practical basis for guiding conservation decisions and environmental interventions within tropical heritage areas.]]>
