This section is from the book "A Treatise On Architecture And Building Construction Vol3: Stair Building, Ornamental Ironwork, Roofing, Sheet-Metal Work, Electric-Light Wiring And Bellwork", by The Colliery Engineer Co.. Also available from Amazon: A Treatise On Architecture And Building Construction.
The next form of covering was probably that of large stones or monoliths, over which flat stoneswere placed (see Fig. 4). In connection with stone roofs we note also the device of corbeling out each course on the two opposite sides, until they meet at the top. See Fig. 5.
The first real roof covering, after the thatch and bough roofs of the nomads, was erected by the Assyrians. These were built of squared timber placed close together and the upper surface covered with thick layers of earth (see Fig. 6). These roofs are said to have been beautified in many cases by varied vegetation, such as flowers, etc. The earlier Egyptians and successive peoples constructed their roofs of flat slabs of stone, supported on stone lintels or beams resting on columns (see Fig. 7), and these, in turn, were succeeded by tiles on boards or vaulted stone roofs.