Revisiting and reanalysing the concept of bioreceptivity 25 years on.

2020 marks 25 years since Olivier Guillitte defined the term 'bioreceptivity', to describe the ability of a building material to be colonised by living organisms. Although Guillitte noted in his 1995 paper that several issues required further investigation, to the best of our knowledge the bioreceptivity concept has not been restated, reviewed, reanalysed or updated since then. The present paper provides an opinionated exposition of the status and utility of the bioreceptivity concept for built heritage science and conservation in the light of current knowledge, aimed to stimulate further discussion. A bibliometric analysis highlights the key dimensions of the past 25 years of published research, showing that the term bioreceptivity has been widely used in the field of built cultural heritage. In our reanalysis of the concept, special attention is devoted to the six types of bioreceptivity (primary, secondary, tertiary, intrinsic, extrinsic and semi-extrinsic) articulated by Guillitte in 1995. We propose that field-based studies of bioreceptivity are urgently needed, and that the intrinsic, extrinsic and semi-extrinsic types of bioreceptivity should be dropped, and a new category (quaternary bioreceptivity) added. Additionally, we propose that bioreceptivity in submerged and subsoil environments should also be considered. Bioreceptivity remains an important concept for managing both new build and built heritage, as it provides the key to understanding the drivers and patterns of biological colonisation of building materials.