A
coffer (or
coffering) in
architecture, is a series of sunken panels in the shape of a square, rectangle, or
octagon in a
ceiling,
soffit or
vault. A series of these sunken panels were used as decoration for a ceiling or a vault, also called
caissons ('boxes"), or
lacunaria ("spaces, openings"), so that a coffered ceiling can be called a
lacunar ceiling: the strength of the structure is in the framework of the coffers. The stone coffers of the
ancient Greeks and
Romans are the earliest surviving examples, but a seventh-century BC Etruscan chamber tomb in the necropolis of San Giuliano, which is cut in soft tufa-like stone reproduces a ceiling with beams and cross-beams lying on them, with flat panels filling the
lacunae. For centuries, it was thought that wooden coffers were first made by crossing the wooden beams of a ceiling in the
Loire Valley châteaux of the
early Renaissance. In 2012, however, archaeologists working under
Andrew Wallace-Hadrill at the House of the Telephus in
Herculaneum discovered that wooden coffered ceilings were constructed in Roman times. Experimentation with the possible shapes in coffering, which solve problems of
mathematical tiling, or tessellation, were a feature of Islamic as well as
Renaissance architecture. The more complicated problems of diminishing the scale of the individual coffers were presented by the requirements of curved surfaces of vaults and domes.