A buttress is an architecture structure built against or projecting from a wall which serves to support or reinforce the wall.
Buttresses are fairly common on more ancient buildings, as a means of providing support to act against the lateral (sideways) arising out of inadequately braced roof structures.
The term counterfort can be synonymous with buttress
and is often used when referring to dams, retaining walls and other structures holding back earth.
Early examples of buttresses are found on the Eanna Temple (ancient Uruk), dating to as early as the 4th millennium BC.
In addition to Flying buttress
and ordinary buttresses, brick and masonry buttresses that support wall corners can be classified according to their ground plan. A clasping or clamped buttress has an L shaped ground plan surrounding the corner, an angled buttress has two buttresses meeting at the corner, a setback buttress is similar to an angled buttress but the buttresses are set back from the corner, and a diagonal (or 'French') buttress is at 135° to the walls (45° off of where a regular buttress would be).
The gallery below shows top-down views of various types of buttress (dark grey) supporting the corner wall of a structure (light grey).
File:Claspingbuttress.PNG|Clasping or clamped buttress
File:Diagonalbuttress.PNG|Diagonal or 'french' buttress
File:Buttress - Palace of Westminster - London - England - 040404.jpg|A buttress and a flying buttress, mostly concealed, supporting walls at the Palace of Westminster
File:Zejtun cultural heritage 11.jpg|Buttress at Our Saviour's Chapel, Żejtun, Malta
File:2014 02 13 16 12 25 Milano ITALY Duomo facciata facade con lampione with street lamp photo Paolo Villa FOTO3972.JPG|Façade buttresses at Milan Cathedral, Italy
File:Barrage Daniel-Johnson2 edited.jpg|Buttresses on the 700ft tall Daniel-Johnson Dam, Quebec
File:Stone Butresses (48013292043).jpg|Thick buttresses characterize Earthquake Baroque architecture like Paoay Church, Philippines
File:Western side of the Great Mosque of Kairouan.jpg|Buttresses of the western side of the Mosque of Uqba in Kairouan, Tunisia
File:Standalone row house in Centralia, Pennsylvania.JPG|Buttresses to support the wall of this row house were constructed after its neighboring house was taken down as part of the Centralia mine fire.