Controls on permeability: implications for stone weathering

In the light of a well-researched relationship between rock properties and susceptibility of stone to weathering, the role of permeability in weathering is examined. A review of weathering studies indicates the varied use and nature of porosity data, but the paucity of permeability studies in weathering trials. Key factors that control porosity and permeability, depositional characteristics and diagenetic processes are discussed and investigated, with a view to discussing the implications for stone weathering. Results from experimental studies on a range of rock types comprising sandstone, limestone and granite are presented. The relevance of permeability measurement is explored in terms of spatial mapping and quantitative assessment of the deterioration of natural building stone. Increased knowledge and appreciation of the inherited characteristics of a rock is demonstrated to provide valuable insight and a greater understanding of how natural stone heterogeneity is accentuated and exploited by weathering and continued exposure to moisture and salts. Mapping the spatial distribution of permeability provides greater insight into the extent of variability in stone deterioration and presents the possibility of monitoring and predicting the hydraulic properties of stone and how these are modified by weathering processes.