Historic building are important for cultural history and provide a variety of habitats for animals and plants. Especially structural heterogenety of wall surfaces is is perceived to support biological diversity. Nevertheless, in traditional approaches goals of biodiversity preservation and monuments restauration are perceived to interfiere and to be mutually exclusive. As a consequence, priority is often given to constructional accepting the loss of local populatiosn and biodiversity. At walls of medieval castles, including an experimental restauration project where conventional and less intesnive restauration techniques where applied, we relate species composition and richness to wall propieties. Especially wall surface structure is quantified using a novel approach. The study focuses on lichens, mosses and vascular plants. Boosted regression tree analyses and non-metric multidimensional scaling techiques are applied to detect the influence of abiotic site conditions on biodiversity. We find species richness to be promoted by wall surface heterogeneity. However, species composition is more affected by restoration approaches than species richeness. Lichen composition varies considerably while vascular plants and mosses are less affected by wall propierties. We suggest strategies that are combining both social targets, the preservation of historical buildings and od species diversity. Careful restauration is capable os supporting both, the maintenance of cultural heritage and of rare and anthropogenic habitats. Wall surface hetereogeinety needs to be witnessed for both aspects as it affects both species composition as well as the effectiveness of cleaning methods.