Flying Buttress

A flying buttress is an external, arched structural support that carries the outward thrust of a vaulted ceiling or roof from the upper wall of a building, across an intervening open space, down to a solid pier or buttress set apart from the building. Central to French Gothic cathedral architecture from the twelfth century onward, seen at Notre-Dame de Paris and Chartres among many others, the technique let masons build taller naves with thinner walls pierced by expansive stained glass, since the vault's thrust was carried externally by the buttress rather than resisted by continuous massive walls. The device is closely identified with the Gothic style, though the underlying principle of an arched external thrust support was also used, less visibly, in earlier and later buildings.