Arc (arch)

In architecture arches appear in many shapes, ranging from a simple round arch to the more complicated multi-foil arch. This blog contains an overview of the various arch types, all entries start with arch.
See also rouleau.

The nomenclature used when describing arches :
1 = clear span (portée)
2 = post (piédroit)
3 = setting-out point
4 = crown
5 = rise (flèche)
6 = start
7 = birth
8 = extrados (extrados)
9 = intrados (intrados or douelles)
The description of the numbers 3, 4, 6 and 7 has been made up by me, based on the Dutch original.

Arc - Wikipedia