Types and Geometries of an Arch

Types and Geometries of an Arch

An arch is a curved structure for spanning an opening and designed to support a vertical load primarily by axial compression.

A Masonry Arch is an arch constructed of individual stone or brick voussoirs.

Keystone is the wedge-shaped, often embellished voussoir at the crown of an arch, serving to lock the other voussoirs in place.

Voussoir are any of the wedge-shaped units in a masonry arch or vault, having side cuts converging at one of the centres.

Extrados, or back, is the exterior curve, surface, or boundary of the visible face of an arch.

Archivolt is a decorative molding or band on the face of an arch following the curve of the intrados.

Intrados is the inner curve or surface of an arch forming the concave underside.

Spring, or springing,  is the point at which an arch, vault, or dome rises from its support.

Rise is the length of an arch from the springing line to the highest point of the intrados.

Surbased arch is an arch having a rise of less than half the span

Horseshoe arch, or Moorish arch, is an arch having an intrados that widens above the springing before narrowing to a rounded crown.

Basket- handle arch, or anse de panier, is a three-centred arch having a crown with a radius much greater than that of the outer pair of curves.

Segmental arch is an arch struck from one or more centres below the springing line.

Round arch is an arch having a continuously curved intrados, specifically a circular one.

Bell arch is a round arch resting on two large corbels with curved faces.

Stilted arch is an arch resting on imposts treated as downwards continuations of the archivolts.

Equilateral arch is a pointed arch having two centres and radii equal to the span.

Drop arch is a pointed arch having two centres and radii less than the span.

Rampant arch is an arch having one impost higher than the other.

Triangular arch is a primitive form of arch consisting of two stones laid diagonally to support each other over an opening.

French arch is a flat arch having voussoirs inclined to the same angle on each side of the centre.

Flat arch, or jack arch, is an arch having a horizontal intrados with voussoirs radiating from the centre below, often built with a slight camber to allow for settling.

Tudor arch is a four-centred arch having an inner pair of curves with a radius much greater than that of the outer pair.

Ogee arch is a pointed arch where each haunch of which is a double curve with the concave side uppermost.

Trefoil arch is an arch having a cusped intrados with three round or pointed foils.

Corbel arch is a false arch constructed by corbeling courses from each side of an opening until they meet at a midpoint where a capstone is laid to complete the work.

Pointed arch is an arch having a pointed crown.

Lancet arch is a pointed arch having two centres and radii greater than the span.