A cloister vault is a vault that springs from all four walls of a room: four curved webs rise and intersect in the corners along arrises that climb diagonally towards the apex. Seen from below it looks like a tent roof built in stone.
The cloister vault is the exact inverse of a groin vault. In a groin vault two barrels intersect so that the groins run from the corners to the centre and the vault cells open onto the walls — leaving four arches in the walls. In a cloister vault the vault surfaces instead sit fully on the walls, and the lines of intersection run up through the corners. Where a groin vault creates four openings, a cloister vault closes the room on every side.
Variants
- Cloister vault on a square plan — four equal webs meeting at a single point
- Cloister vault on a rectangular plan — the four webs meet not at a point but along a ridge
- Truncated cloister vault (mirror vault) — the apex is replaced by a flat central panel, the mirror; much used in eighteenth- and nineteenth-century halls
- Cloister vault on a polygon — over an octagonal room, for example, with as many webs as sides
Where it applies
- Monastic refectories, chapter houses and cellars — the source of the name
- Bays in churches and cloister walks
- Cellars and gate passages where load from above has to be spread evenly
- Formal halls in the form of a mirror vault, often executed in plaster
Structural behaviour
A cloister vault transfers its loads to all four walls along their whole length, not to four points as a rib vault does. That spreads the load more evenly, but it also means thrust acts along the entire wall: the walls have to be thick enough, or a tie or buttress is needed. Cracking along the corner arrises of an old cloister vault nearly always points to walls spreading, not to a problem in the vault itself.
Practical tips
- Have cracks assessed — use a tell-tale or crack monitor to establish whether a crack is live before you close it; filling a moving crack achieves nothing
- Point soft — repoint historic vaults with lime mortar, not cement
- Do not load unevenly — concentrated loads on the back of a vault, such as storage on the floor above, are the classic cause of damage
- In new build — a masonry vault requires accurate centring and is specialist work
Related terms
- Vault
- Groin vault
- Vault bay
- Vault rib
- Bohemian vault
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