Inner vaulting is the curvature on the inside of an arch or vault, as visible from the interior. It refers to the concave inner surface that defines the shape and spatial character of a vaulted structure. The inner vaulting determines how the vault looks from below and plays a key role in the structural behaviour of the arch.
Anatomy of a vault
A vault is a curved structural element that spans an opening, transferring loads to the supports (piers or walls) at either side. The inner vaulting — also known as the intrados — is the lower, concave surface of the vault. The outer surface is called the extrados.
Key elements related to inner vaulting include:
- Intrados — The technical term for the inner curved surface of the vault. The intrados is what you see when you look up at a vaulted ceiling.
- Keystone — The central stone at the crown of an arch. It is the last stone placed during construction and locks the other stones (voussoirs) into position.
- Ribs — In ribbed vaults, structural ribs project from the inner vaulting surface, dividing it into panels. The ribs carry the loads while the panels between them can be thinner and lighter.
- Springing point — The point where the curvature of the inner vaulting begins, at the top of the supporting wall or pier.
Types of inner vaulting profiles
The shape of the inner vaulting defines the type of vault:
- Barrel vault — A continuous semicircular or pointed curve, forming a tunnel-like space.
- Groin vault — Created by the intersection of two barrel vaults at right angles, producing a curved X-pattern on the ceiling.
- Ribbed vault — Similar to a groin vault but with added ribs along the intersections, common in Gothic architecture.
- Dome — A vault that curves in all directions from a central point, creating a hemispherical inner surface.
The profile of the inner vaulting affects both the aesthetics and the acoustics of a space. Vaulted ceilings reflect sound differently than flat ceilings, which is why churches and concert halls often feature carefully designed vault profiles.
Related terms
- Vault
- Arch
- Intrados
- Rib
- Keystone
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