An integrated study of the microorganisms growing on the weathered sandstone of the church of Carrascosa del Campo (Spain) was carried out. Whilst lichens played only a minor role in colonization, algae and bryophytes were abundant in the sandstone and mortars on the north facade. Although the contribution of algae to deterioration is considered less important, they supported the colonization and development of an allied heterotrophic population of bacteria and fungi, and ultimately, after organic matter decomposition and humification, led to mosses and plants which could have a higher deterioration potential.