How did rib vaults reduce the weight of a Gothic cathedral ceiling?

Rib vaults reduced the weight of a Gothic cathedral ceiling by utilizing a skeleton of intersecting stone ribs to support the structure. Unlike traditional barrel or groin vaults that required heavy, continuous masonry, the rib vault allowed the ceiling surface to be composed of mere thin stone panels.12

By concentrating the weight of the vault at discrete points—the ribs—rather than along a continuous wall edge, the overall mass of the ceiling was significantly decreased. This reduction in weight also minimized the outward thrust that previously necessitated thick, heavy walls. Consequently, the load could be transferred to widely spaced vertical piers, allowing for thinner walls and the inclusion of large windows. The integration of pointed arches further assisted by distributing thrust more effectively in downward directions.12