Arch

The arch is the oldest and most elegant way to span wide openings with materials such as stone or brick, which are weak in tension but strong in compression. Wedge-shaped blocks called voussoirs are laid along a curve and locked at the top by a keystone. Loads follow the curve down into the supports on either side. In doing so the arch also pushes outwards, which is why its piers must be thick or braced by buttresses. In Turkish it is kemer.

Types of arch

Roman architecture used the semicircular arch everywhere from aqueducts to triumphal arches. In Gothic architecture the pointed arch sent loads down more steeply and opened the way to taller, slimmer buildings. Islamic and Ottoman architecture made characteristic use of pointed, horseshoe and segmental arches in arcades, around courtyards and in the systems that carry domes. Extend an arch horizontally and you get a vault; rotate it around its axis and you get a dome.

Arches today

Reinforced concrete and steel removed the structural need for arches, yet the form lives on in bridges, long-span roofs and as a design language in interiors. Arched doorways and niches give homes a soft, warm character.

In restoration and reconstruction projects, the stone coursing, joints and exact curve of an arch should follow the measured survey faithfully. In visualisation, those details are what bring out a building’s historic character.