HOW THE ROMANS BUILT ARCHES AND DOMES.

HOW THE ROMANS BUILT ARCHES AND DOMES. This wikipedia article describes the traditional way that Roman arches were constructed: “An arch requires all of its elements to hold it together, raising the question of how an arch is constructed. One answer is to build a frame (historically, of wood) which exactly follows the form of the underside of the arch.” A similar technique was apparently used for domes. The circular part of the upper dome of the Pantheon, according to this article, “was likely placed by using wooden scaffolding.” One of the secrets of the Pantheon is that lighter stone was used at the top: “The upper dome above the step-rings (the top 30 feet/9.1 m) is concrete comprising about 9 inch lumps of light tufa and porous volcanic slag in alternating layers bonded with mortar.” Apparently we can now build a dizzyingly high arch without scaffolding or a framework underneath.