buttress

A buttress is a projecting support built against a wall to reinforce it and resist lateral forces. By transferring thrust from arches, vaults, or earth pressure down into the ground, buttresses help prevent outward bowing or collapse of the wall. They are used in masonry and concrete construction and can be integrated into the wall or separated as a distinct element.

There are several common types. A traditional external buttress is a thickened wall extension that pushes against the wall to counteract horizontal thrust. A flying buttress is a slender arch or series of arches that transfers thrust from the wall to a detached vertical support, typically away from the wall itself; this arrangement is a hallmark of many Gothic cathedrals and enables higher walls with large windows. Counterforts are triangular or wedge-shaped supports attached to the exterior of a retaining wall at intervals to resist bending and outward forces. Some buttresses are purely structural, while others are combined with decorative treatment.

Historically, buttresses played a crucial role in ancient and medieval architecture. They enabled the construction of tall, wide-spanned walls and expansive openings by countering the push of vaulted ceilings and heavy roofs. The development of flying buttresses in the Gothic period marked a turning point in architectural design, allowing unprecedented verticality and illumination.

In modern construction, buttresses continue to be used in engineering contexts such as dam, bridge, and tower foundations, as well as in reinforced concrete and masonry walls, where additional support is required to resist lateral loads.