Glossary · G
Groin
Also called groins
The curved arris formed where two vault surfaces intersect.
See also: Groin vault
Rules that use the word
Two barrels crossed gather their thrust at the corners. Intersect two barrel vaults of equal height at right angles: the result is a groin vault, whose weight and thrust are gathered along the diagonal groins to the four corners, leaving the sides free for openings.
The cloister vault: the groin turned inside out. Where the groin vault is the union of two barrels, the cloister (domical) vault is their intersection: four curved cells rise from all four walls and meet in valleys along the diagonals. It needs walls on every side.
The problem of the oblong bay. Two semicircular barrels of different spans rise to different heights. To groin-vault an oblong bay the narrower barrel must be stilted or flattened, and the groins then wander out of plane: the difficulty that pushed builders towards ribs and pointed arches.
Where it appears in the book
In the chapters The Arch, Vaults, The Classical World, Romanesque and Gothic.
A feature of Ancient Roman, Romanesque architecture.
Nearby in the glossary
Going · Golden section · Gong · Gopuram · Groin vault · Grotto · Guldasta · Guttae