Coupling electrical resistivity methods and GIS to evaluate the effect of historic building features on wetting dynamics during wind-driven rain spells

Abstract

Moisture is one of the most important factors causing building stone decay and rain penetration is one of the leading factors. Particularly, wind-driven rain spells, which are becoming increasingly common and seasonal as a result of climate change. Historic buildings' sometimes intricate design features can be a factor multiplying meteorological anisotropy, either shielding walls or increasing the surface that is affected by wind-driven rain spells. This paper aims to identify the effect of pilasters and tower buttresses on the wetting dynamics of a listed 9th Century historic building during a rain spell by means of electrical resistivity methods coupled with GIS mapping, paying special attention to how data representation and map algebra can improve the interpretation of several data sets of non-destructive testing. Results show how building features can modify deeply moisture dynamics and maximise local anisotropy. In the present case, a compound of an external tower buttress and an internal pilaster decreases moisture ingress through ground infiltration while increasing moisture retention into the wall due to its larger mass. This, in turn, multiplies the incidence of moisture-related processes inside the building. The presented data also highlight the usefulness of mapping over time (4D mapping) and of GIS to improve interpretations through map algebra.