What is a tierceron?
A tierceron is a secondary rib in a Gothic rib vault that rises from the springing point (where the vault starts on the pier or wall) to the ridge rib, without passing through the central keystone. The word comes from French: tiers means third. After the diagonal ribs and the transverse and wall arches, the tierceron is, as it were, a third kind of rib.
How to recognise a tierceron
In a simple quadripartite rib vault, only two diagonal ribs run from corner to corner. In a vault with tiercerons, extra ribs spring from the same point and fan out towards the ridge rib, either along the length or across the width of the vault. Seen from below, this creates a star-shaped or palm-like pattern.
Tierceron and lierne
- A tierceron always starts at a springing point.
- A lierne does not start at a springing point but connects two other ribs. Liernes are found mainly in late Gothic stellar vaults and net vaults.
Function and history
Tiercerons divide the vault surface into smaller fields. This made it easier to build the vault webs between the ribs and gave Gothic master builders great decorative freedom. Their structural contribution is limited: the forces are carried mainly through the webs and diagonal ribs to the piers and buttresses.
Tiercerons first appeared in England in the 13th century, for example in Lincoln Cathedral. The nave of Exeter Cathedral is a famous example of a long, continuous tierceron vault. Later they spread to the Continent, often combined with liernes in stellar vaults.
Related terms
- Lierne
- Vault rib
- Rib vault
- Stellar vault
- Net vault
- Vault keystone
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