A coffer is a recessed panel. Ceilings covered with coffers were known in ancient Greek architecture. They had considerable importance in Roman houses (Vitruvius 7.2) and temples and were occasionally used in Egyptian buildings in the Roman, Byzantine, and early medieval periods. Coffers were made in flat wooden ceilings by subdividing the space between the large ceiling beams with short transverse beams. The areas thus formed, usually rectangular, were closed off on top by boards, which served as the substructure for the floor above. The beams could either be adorned with carved work or covered with wood, metal, or terra-cotta.
In Roman vaulting, which usually consisted of a concrete shell made of small chips of stone or broken bricks and mortar, coffers were used as decorative forms on the undersurface of the vault, since the recesses could be very easily accommodated by the requisite thickness of the vault. Such coffers could take on triangular or polygonal forms. Famous examples are the vaults of the Pantheon and the Temple of Venus and Roma in Rome.
How far coffers were employed in Christian basilicas has not yet been determined with any certainty. Despite some basilicas in the city of Rome that certainly had a ceiling, several indications suggest that most basilicas probably had an open-frame roof (Deichmann, 1957, pp. 249ff.). Nevertheless, there is evidence that individual parts of churches had a ceiling.
That there were coffered ceilings in Egypt in the Roman and early Byzantine periods is shown by a number of wooden boards preserved in the Coptic Museum, Cairo. Some have a richly bordered painted surface but at the edges generally show no painting at all (Deichmann, 1972, pp. 83ff.). There is hardly any doubt that these are panels from ceilings. Terra-cotta slabs with pictorial motifs to cover coffers were found in Alexandria (Wace, 1948, pp. 50f., pl. 3). In several tombs in Alexandria, coffers were simply painted on the ceiling (Adriani, 1940-1950, pp. 36-40, ills. 43 and 53, pl. A and B).
In the same way, the former presence of a coffered ceiling may be deduced in some structures from an unusually close positioning of the beams. One example is the annexed southeast corner room of the church built into the front of the Temple of Isis at Philae under Bishop Theodorus in the eighth century. Another is the later baptistery in the newly discovered central church of Makhurah al-Qibli on the Mediterranean coast (Grossmann, 1980, pp. 225ff., pl. 50b). Both instances, moreover, involve false ceilings closing off an area above. Finally, over the central area of the khurus in the old church of Dayr Anba Antuniyus, there is an interesting coffered ceiling curved as a barrel vault in an imitation of gypsum, where wide boards with a series of octagonal openings sawn in them have been inserted into the spaces between the beams (Grossmann, 1982, p. 50, pl. 59a).
- Adriani, A. “Nécropolis de l’île de Pharos.” In Annuaire du Musée gréco-romain, Vol. 3, pp. 47-128. Alexandria, 1940-1950.
- Deichmann, F. W. “Untersuchungen zu Dach und Decke der Basilika.” In Charites: Studien zur Altertumwissenschaft, ed. K. Schauenberg. Bonn, 1957.
- . “Kassettendecken.” Jahrbuch der österreichischen Byzantinistik 21 (1972):83-107.
- Durm, J. Baukunst der Etrusker und Römer, pp. 244ff. Stuttgart, 1905.
- Gross, W. H. “Lacunar.” Der kleine Paulys 3 (1975):441f. Grossmann, P. “Arbeiten in Mahura al-Qibli.” Mitteilungen des
- Deutschen Archäologischen Instituts—Abteilung Kairo 36 (1980):225ff, pl. 50b.
- . Mittelalterliche Langhauskuppelkirchen und verwandte Typen in Oberägypten. Glückstadt, 1982.
- Wace, A. J. B. “Later Roman Pottery and Plate.” Bulletin de la Société d’archéologie d’Alexandrie 37 (1948):50f., pl. 3.