A vault rib is a projecting, arch-shaped structural band that runs along the intersection lines of a vault, supporting and reinforcing the vault webs. Vault ribs form the skeleton of a ribbed vault: they collect the forces and transfer them to the piers or walls.
Function of vault ribs
- Load-bearing — the ribs carry the vault webs and direct forces to the supports
- Structural efficiency — by using ribs, the rest of the vault (the webs) can be built thinner and lighter
- Construction simplification — the ribs are built first, then the webs are filled in between them
- Decoration — ribs are often moulded and ornamented
Types of ribs in a vault
| Rib | Position |
|---|---|
| **Diagonal rib (ogive)** | Runs diagonally across the vault, from corner to corner |
| **Transverse rib** | Cross rib between two vault bays, perpendicular to the longitudinal axis |
| **Wall rib (formeret)** | Rib along the wall, parallel to the longitudinal axis |
| **Lierne** | Short decorative rib that does not start from a support point |
| **Tierceron** | Extra rib from a support point to a point on the diagonal rib |
Vault rib vs. groin
- Groin — the sharp intersection line between two vault webs, without a projecting profile (in a groin vault without ribs)
- Rib — a separately built or carved structural element that projects above the vault surface
The ribbed vault was a major innovation in Gothic architecture: it made larger spans and taller spaces possible.
Identification
Vault ribs can be recognised as the arch-shaped bands running across the ceiling of a church or cellar, converging at a central point (the vault keystone).
Related terms
- Vault
- Vault web
- Vault keystone
- Pier
- Springing point