The New International Encyclopædia/Groined Vaulting
GROINED VAULTING (from groin, earlier grine, variant of grain, from Icel. grein, branch of a tree). In architecture, that vaulting in which two barrel vaults intersect each other at right angles, on a square plan, and with semicircular curve. The arris or salient edge formed at the lines of intersection is called the groin. Such vaults were usually small, and employed in considerable numbers, forming a connected series of square vaulting compartments. It was a form first extensively used in Roman architecture, and continued throughout the early Middle Ages, where it is found especially in the side aisles of churches, though also sometimes in the naves. It was superseded during the twelfth century by ribbed vaulting (q.v.), a much stronger and more elastic form of cross-vault. Roman examples are in the passageways and galleries of amphitheatres on a small scale, and in the halls of thermæ on a large scale.