Exterior buttresses are architectural elements designed to support structures by applying lateral force to exterior walls, primarily to counteract outward thrusts and enhance overall structural stability. They are essentially projecting supports built against a building's wall.
The Role and Function of Exterior Buttresses
Buttresses serve as crucial structural reinforcements, projecting outward from the main wall of a building. Their primary purpose is to provide robust support, particularly against lateral (sideways) forces that can push walls outward. These forces often arise from heavy roofs, vaults, or arches, which exert significant outward pressure, especially in large structures like cathedrals or older masonry buildings.
How They Work
The fundamental principle behind an exterior buttress is to absorb and redirect the outward thrust generated by the building's internal components. By extending from the wall, the buttress creates a wider base and a stronger resistance point, pushing back against the lateral forces and preventing the wall from buckling, cracking, or collapsing. This allows for thinner walls and larger openings (like windows) than would otherwise be possible in structures relying solely on wall thickness for support.
Historical Significance
The use of buttresses dates back to ancient times, with early forms found in Roman architecture. However, they became a defining and highly sophisticated feature of Gothic architecture during the Middle Ages. The development of the flying buttress, in particular, was a revolutionary innovation that enabled the construction of taller, grander cathedrals with vast stained-glass windows, as it allowed the immense weight of the vaulted ceilings to be transferred to external supports rather than requiring massive, thick walls.
Types of Exterior Buttresses
Buttresses vary in form and complexity, each designed to address specific structural needs:
- Plain Buttress: A simple, solid mass of masonry projecting from the wall, often tapering as it rises.
- Setback/Stepped Buttress: A buttress that diminishes in thickness at various stages as it rises, creating a stepped appearance.
- Angle Buttress: Formed by two buttresses meeting at the corner of a building.
- Diagonal Buttress: A single buttress placed diagonally at the corner of a building.
- Flying Buttress: The most iconic type, consisting of an arch (or series of arches) spanning from an exterior wall to an independent pier, transferring the lateral thrust over an open space. This innovation allowed for much lighter walls and larger windows in Gothic cathedrals.
- Clasping Buttress: A buttress that completely encloses the corner of a building.
Table: Common Types of Exterior Buttresses
| Type | Description | Primary Use |
|---|---|---|
| Plain | Solid, projecting mass of masonry, often tapering. | General wall reinforcement, older structures. |
| Setback/Stepped | Receding in stages, providing support at different heights. | Gothic cathedrals, large masonry buildings. |
| Flying | Arch(es) transferring thrust from upper wall to a freestanding pier. | Iconic in Gothic cathedrals for tall, light walls. |
| Angle/Diagonal | Located at building corners for multi-directional support. | Corner stability in various architectural styles. |
| Clasping | Encloses a corner entirely, offering substantial corner reinforcement. | Enhanced corner strength, often integrated decoratively. |
Construction Materials and Methods
Historically, buttresses were constructed from durable materials such as:
- Stone: The most common material, especially in historical structures, due to its compressive strength and longevity.
- Brick: Used in many masonry buildings, offering flexibility in construction.
- Concrete: Modern buttresses might utilize reinforced concrete for its strength and versatility.
The construction method typically involves building the buttress integral to the wall or as a separate, adjoining structure, ensuring a strong connection to effectively transfer forces.
Modern Applications and Preservation
While not as prevalent in contemporary lightweight construction, buttresses are still essential in the preservation and renovation of historic buildings. They are crucial for maintaining the structural integrity of unreinforced masonry structures. Modern architects might also use them for aesthetic reasons or in specialized designs where heavy loads or unique structural challenges require robust external reinforcement.
For further information on the structural principles behind buttresses, you can explore resources on architectural engineering or Gothic architecture.
