(CE: 194a-226a) 
Roof. A roof is the top covering of a building and its supporting frame. It may be flat, saddleback (pitched), or vaulted. In Egypt since earliest times, the flat roof was preferred. Probably from the Hellenistic period, saddleback roofs were used only for buildings that had an unusually wide span, such as classical temple complexes, market buildings, and especially churches. Stone vaults were rare and were used only in areas where wood for roof beams and frames was not available. Even the earliest sepulchers, however, were built of lasting materials. Churches from the Fatimid period on used vaulting because it was less liable to be damaged by worms or fire, a change specifically mentioned in the sources.
The construction of a flat roof was essentially that of a ceiling (see above). It required additional precautions, however, to ensure the trouble-free draining of rainfall. The surface was strengthened with a layer of stones or bricks that were then completely covered by a coat of plaster, in order to seal all openings. To make it more solid, the plaster was often enriched with chips of burnt brick, producing a weatherproof mortar akin to opus signium developed in
the Roman period. Roof tiles were not known in Egypt. Since the upper edges of a building can be easily damaged by wind and rain, the edges of the roof were always provided with at least a low wall. Higher buildings required a parapet. The surface of the roof was given either a slope or separate water channels, which let rain water flow into gutters at the edge of the roof.
Two drainage systems were in use in the pharaonic period. In large, high buildings, waterspouts projecting clear of the wall surfaces were employed, as at Dayr Anba Shinudah, which prevented the wind from splashing the water against the walls. In smaller buildings, including such pharaonic temples as that of
Ramses II at Abydos, a somewhat simpler system involved water channels built into the wall itself. Buildings of mud brick had to be plastered with a lime mortar and required a device at the foot of the wall to keep the water away from it, since otherwise there was a danger that the foundations would wash away. Sometimes the water was led into cisterns to be used as drinking water (Grossmann, 1967, pp. 463ff.). That was particularly true of the hermits' houses in the lauras of Kellia and Abu Mina.
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