Roof tiles are overlapping tiles designed mainly to keep out precipitation such as rain or snow, and are traditionally made from locally available materials such as clay or slate. Later tiles have been made from materials such as concrete, and plastic.

Slate is a fine-grained, foliated, homogeneous, metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low-grade, regional metamorphism. It is the finest-grained foliated metamorphic rock. Foliation may not correspond to the original sedimentary layering, but instead is in planes perpendicular to the direction of metamorphic compression.