When talking to a stonemason, bricklayer or architect about arch construction all involved need to be coming from the same page, in other words, have a good understanding of the different components that make up an arch is important to ensure good communication skills and ensuring that wall is talking about the right component.
I have put together some drawings with arch terminology.
Arch Terminology
Keystone:
The voussoir located at the crown of the arch. Also called the key.
Label Course:
A ring of projecting can be flush using brickwork or Stone that forms the extrados of the arch.
Wing:
An arch used over the triple opening of the so-called Venetian or Palladian window, flat over the narrow side lights, round over the larger central opening.
Centre of the Arch:
The centre of the arch as the name suggests is the halfway point between the abutments, which is normally the last masonry component whether it be a keystone or brick which completes the construction process.
Arch Terminology
Creepers:
Creepers are bricks which have been cut to an angle around the upper curve of an arch called the Extrados leaving approximately 10mm mortar joint
Crown:
The highest point on the external curve of an arch or the Extrados, in symmetrical arches, the crown is at the midspan.
Extrados:
Extrados is the outer or upper curve of an arch
Intrados:
The internal or lower curve line of an arch, while the soffit is a surface.
Span:
The clear horizontal distance between abutments.
Abutment:
The abutments of an arch are located at each end of the span of the arch opening, the primary function of the abutments is to carry the load was being transferred through the arch.
Arch Terminology
Depth:
This is the measurement between the intrados & extrados, sometimes called the Height
Springing Line:
This is the imaginary horizontal line joining the two springing points.
Rise:
The maximum height of the arch soffit above the level of its spring line.
Radius:
The radius of a circle is the length of the line from the center to any point on its edge.
Springer:
The first voussoir from a skewback.
Voussoir:
Voussoir is one masonry unit of an arch, this can be a header all stretcher which is cut to a wedge shape to construct the arch.
Brickwork Face:
The brickwork face surface area is the front face of the flat elevation of the arch.
Arch Terminology
Skewback:
The surface on which the arch joins the supporting abutment.
Skewback Angle:
The angle made by the skewback from horizontal.
Striking Point:
The centre of a circular arch curve and the point from which the voussoirs radiate.
