Imbrex and Tegula

The imbrex and tegula system is the roof tiling method used across the ancient Greek and Roman world. A tegula is a flat tile, usually with raised side edges, laid on the roof slope; an imbrex is a half-cylindrical tile laid over the joint between two neighbouring tegulae. Together they form a ribbed, weathertight roof that needed little or no extra sealing when well made.

Origins

The Greeks made the first tiles of this kind, pressing wet clay into four-sided moulds and firing it in kilns. Some of the earliest fired roof tiles come from temples near Corinth, dated to around 700-650 BC. Early tegulae were flat or had a single ridge to hang them on the slope; later ones gained raised borders to channel water, and some borders converged towards the lower end so tiles nested together.

Marble tiles came into use around 620 BC and were used on major temples, including the Temple of Zeus at Olympia and the Parthenon. Bronze and gilded tiles were used on a few especially prestigious buildings.

Roman use

In Rome, tiles replaced wooden shingles and were used on nearly every type of building. Tiles were made in vast numbers, and those produced by army units were often stamped with the legion's insignia, which helps archaeologists date sites. A 1993 excavation in Merseyside, England, recovered over 300 kg (660 lb) of tile and kiln material, some stamped by Legio XX Valeria Victrix. Broken tiles were commonly crushed and reused in mortar.

Roof details

Decorated end pieces called antefixes closed the open ends of the imbrices along the eaves. Gutters ran above the cornice, with spouts often carved as lions' heads or grotesque faces.

Legacy

The pan-and-cover principle survives in modern two-piece curved tiles such as mission or barrel tiles, and in the German Mönch und Nonne (monk and nun) tile. The English word "imbrication", meaning an arrangement of overlapping layers, comes from imbrex.