Walls.
The walls are uniformly thick, and often of granite or of stone, though brick is also met with; e.g. some of the smaller pyramids are built entirely of brick. In all probability the walls of domestic buildings were to a great extent of brick, and less thick than those of the temples; hence they have all disappeared.
The surface of walls, even when of granite, was usually plastered with a thin fine plaster, which was covered by the profuse decoration in colour already alluded to.
The walls of the propylons tapered from the base towards the top, and the same thing sometimes occurred in other walls. In almost all cases the stone walls are built of very large blocks, and they show an unrivalled skill in masonry.
Roofs.
The roofing which remains is executed entirely in stone, but not arched or vaulted. The rock-cut tombs, however, as has been stated, contain ceilings of an arched shape, and in some cases forms which seem to be an imitation of timber roofing. The roofing of the Hypostyle Hall at Karnak provides an arrangement for admitting light very similar to the clerestory of Gothic cathedrals.
Openings.
The openings were all covered by a stone lintel, and consequently were uniformly square-headed. The interspaces between columns were similarly covered, and hence Egyptian architecture has been, and correctly, classed as the first among the styles of trabeated architecture. Window-openings seldom occur.