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Arch
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An arch is a structure that spans a space while supporting mass (e.g. a doorway in a stone wall). Arches appeared as early as the 2nd millennium BC in Mesopotamian brick architecture and their systematic use started with the Ancient Romans who were the first to apply the technique to a wide range of structures.
Elements of an arch:
Voussoir is a wedge-shaped element, typically a stone, (piatra) used in building an arch.
Keystone or Key is the architectural piece at the crown of a vault or arch which marks its apex, locking the other pieces into position.
Springing line is the start of the arch.
Rise is the distance from the springing line of the arch to the top of the arch.
Arch types
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| Lintel arch | Segmental arch | |
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| Semi-circular arch | Three centred arch | |
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| Parabolic arch | Lancet arch | |
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| Drop arch | Horseshoe arch | |
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| Ogee arch |
Drawings by Frank Gaylard from: Fisher, Roger C. 1992. Visual Lexicon of the South African Dwelling. Cape Town: Unibook. p, 10.