What are “flying buttresses” mainly used for?

The story behind the answer

A flying buttress is an arched masonry strut that carries the outward thrust of vaulted ceilings and roofs away from a church’s upper walls to a separate pier, preventing collapse. By redirecting these lateral forces, builders could make walls much thinner and taller, opening space for vast stained-glass windows and soaring interiors.

Emerging in 12th‑century Gothic architecture in France (think Notre‑Dame, Chartres, Reims), this innovation replaced the heavy, fortress-like walls of the Romanesque style with light-filled, “skeletal” structures. Although often elaborately carved and visually striking, their role is fundamentally structural. A common mix-up: gargoyles channel rainwater; buttresses handle the physics of stone vaults and wind loads, enabling the dramatic heights that defined medieval cathedrals.