http://www.egyptology.nl/pdf/art5zond.pdf Willockx, Sjef (2003) Building in stone in Ancient Egypt, Part 1: Columns and Pillars] Photograph of the barrel vaults at the Ramesseum Architectural elements used by ancient Egyptian builders  The span was 12 feet and the lower part of the arch was built in horizontal courses, up to about one-third of the height, and the rings above were inclined back at a slight angle, so that the bricks of each ring, laid flatwise, adhered till the ring was completed, no centering of any kind being required; the vault thus formed was elliptic in section, arising from the method of its construction.