The impact of laboratory-grown subaerial biofilms on water-transport properties of Lecce stone

Water plays a key role in the durability of building materials, including stone-built heritage. A primary contributor to the weathering mechanisms affecting stone materials exposed outdoors, water is also essential to regulate colonization by subaerial biofilms (SABs). Recent studies have suggested that SABs influence water transport properties of biocolonized porous substrates, potentially offering protective effects by reducing surface wettability and slowing capillary water absorption. However, their impact on moisture sorption, drying rate, and water vapor permeability remains unclear. To systematically investigate how SABs influence water and moisture transport in porous stone materials, reproducible, well-characterized laboratory models are essential. Current methods often result in uneven SAB formation and distribution, limiting the reliability of experimental results. Therefore, an existing protocol was optimized to ensure complete and homogeneous SAB coverage. Such optimized stone-SAB models allow for quanti tative measurements of capillary absorption, drying rate, hygroscopic sorption, and water vapor permeability with greater precision and reliability than previously achievable. Subsequently, the effects of laboratory-grown mono-species and dual-species SABs on such properties were evaluated. The results confirm the potential of SABs in reducing capillary absorption and provide new insights into moisture dynamics in the SAB-stone system, a key aspect that remains poorly un derstood. Overall, this study advances the understanding SAB–substrate interactions and aims to contribute to a shift in perspective regarding biocolonization in built environment conservation.