Definition of Roofing Slate Lithotypes for an International Roofing Slate Classification

The term “roofing slate” comprises all natural rocks that can be used for roofing. Some of the characteristics that define their performance as construction materials are water absorption, bending strength, mineral composition, and aesthetics. From a sustainability point of view, roofing slates also have the largest life expectancy and lowest carbon emissions of all covering materials. This work reviews the constructive characteristics of roofing slates, from technical data provided by producers from all over the world. These data, supported by the petrological characterization of several roofing slate samples, are used to propose a general classification for this special type of rock. Thus, roofing slates are sorted in twelve lithotypes, depending of their petrographical characteristics, defined by the color. The resulting classification is named International Roofing Slate Classification (IRSC), formally defined in this paper.