Vaults - what they are, types of vaults and their construction

abutment, filling of the extrados of the vault
abutment, filling of the extrados of the vault

The vault, conceptually, is a combination of many arches together to the point of fully covering an entire room. A big disadvantage is the requirement to start the walls from their impost plans.


The vaults have certain characteristics:

- statically the (vertical) loads are distributed on the supports by means of mutual contrasting actions, determining forces with horizontal components which will be absorbed by walls (of the right thickness) or alternatively by certain masonry works, such as buttresses (for further information go here).

- the ribs are very complex for their formation;

- the intrados is more or less lowered and can take on different types of curvature;

- it has a decidedly high own weight due to the filling on the extrados, which is also called abutment, necessary for the creation of flat surfaces for the floors of the upper rooms, and to counteract the thrust of the vault.


The geometric shapes that a vault can have are different and vary according to the plan and the level of the tax plane: straight vault with rectangular plan, oblique vault with rhomboidal plan, conical vault with trapezoidal plan and rampant vault with tax plans inclined.




A simple vault is characterized by a geometrically rectangular intrados (cylindrical or spherical). They in turn are divided into:

- Barrel vaults, are distinguished by having a transversal section formed by an arc of a circle or ellipse or more arches (in the latter case it will be a polycentric vault, while the circular ones are round or depressed vaults). These types of vaults insist on opposite sides of the plan, forming the impost planes that will support the loads;

- basin vaults, have the intrados with a spherical surface on a circular plan. They transmit loads uniformly over the entire circumference of the impost plane;

- ribbed vaults, also in this case have a spherical extrados, but on a square or polygonal plan. In this case the loads are concentrated above all in the vertices of the plant.



To understand the geometric conformation of these vaults it is necessary to start from the sectioning of a barrel vault. The sectioning involves two diagonals starting from the vertices of the plant, through the plant itself and the vault. From this we obtain the spindles, in the plant, and the nails, in the vault part. They are divided into:

- pavilion vaults, are obtained by combining two pairs of barrel vault spindles with the same mount (by mount we mean the curvature of the vault). In this way they will rest continuously on the four sides of the plant;

- cross vaults, are obtained by combining two pairs of nails originating from barrel vaults with the same mount, which concentrate the loads at the four vertices of the plan. From here the combination will be with columns or pillars that absorb the vertical loads .



Their construction is completely similar to that of arches (for further information go here). The three main phases are:

- formation of the rib, these ribs must have double-curved surfaces and must be non-deformable;

- installation of the vault, the bricks are laid with differently oriented courses, increasing their structural capabilities and ensuring adequate bonding;

- disarmament of the curtainsider.

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