Importance of Keystone,Springers,Voussoirs-Architectural Arches StLouis Brick Building

Keystone (architecture)

Decorative Lion Head Keystone

Location of Keystone-Architectural Arch

From Wikipedia, the free encyclopedia: 

A keystone is the wedge-shaped stone piece 

at the apex of a masonry vault or arch, which 

is the final piece placed during construction 

and locks all the stones into position, allowing 

the arch to bear weight. 

Although a masonry arch or vault cannot be 

self-supporting until the keystone is placed, 

the keystone experiences the least stress 

of any of the voussoirs, 

due to its position at the apex.

Keystone, Springers, Voussoirs StLouis Brick Building

Voussoir

From Wikipedia, the free encyclopedia

A voussoir (pronounced /vuˈswɑr/) is a wedge-shaped element, 

typically a stone, used in building an arch or vault.

Although each unit in an arch or vault is a voussoir, 

two units are of distinct functional importance: 

the keystone and the springer. 

• The keystone is the center stone or masonry unit 

            at the apex of an arch. 

• The springer is the lowermost voussoir, 

located where the curve of the arch springs from the 

vertical support or abutment of the wall or pier.

The word is a mason's term borrowed in Middle English from 

French verbs connoting a "turn" (OED). Each wedge-shaped 

voussoir turns aside the thrust of the mass above, transferring 

it from stone to stone to the springer's bottom face ('impost'), 

which is horizontal and passes the thrust on to the supports. 

Voussoir arches distribute weight efficiently and take maximum 

advantage of the compressive strength of stone, as in an arch bridge.

In Eastern Romanesque and Arab architecture the voussoirs are 

often in alternating colors, usually red and white.

During the 18th and 19th centuries British bricklayers became 

aware that by thickening the vertical mortar joint between regularly 

shaped bricks from bottom to top they could construct an elliptical 

arch of useful strength over either a standard 'former' or over 

specially constructed timber false work, (work to be removed following 

the construction of the prime). The bricks used in such an arch 

are often referred to as 'voussoirs'.