Coffer

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 was often 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.

History

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. Coffering is known as zaojing (Chinese: 藻井; pinyin: zǎojǐng) in ancient Chinese wooden architecture.

It was thought for centuries that wooden coffers were first made by crossing the wooden beams of a ceiling in the Loire Valley châteaux of the early Renaissance. However, archaeologists working at the House of the Telephus in Herculaneum in 2012 discovered that wooden coffered ceilings were constructed in Roman times. A prominent example of Roman coffering, employed to lighten the weight of the dome, can be found in the ceiling of the rotunda dome in the Pantheon, Rome.

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. Coffered ceilings were used in cathedrals starting with St Mark's Basilica and Santa Maria Maggiore.