A pilaster is a slightly-projecting flattened column built into or applied to the face of a wall. In discussing Leon Battista Alberti's use of pilasters, which Alberti reintroduced into wall-architecture, Rudolf Wittkower wrote, "The pilaster is the logical transformation of the column for the decoration of a wall. It may be defined as a flattened column which has lost its three-dimensional and tactile value."[1]
Pilasters often appear on the sides of a door frame or window opening on the facade of a building, and are sometimes paired with columns or pillars set directly in front of them at some distance away from the wall, which support a roof structure above, such as a portico. These vertical elements can also be used to support a recessed archivolt around a doorway. The pilaster can be replaced by ornamental brackets supporting the entablature or a balcony over a doorway.
As with a column, a pilaster can have a plain or fluted surface to its flattened rectangular profile (cross section) and can be represented in the mode of any of the classical orders. In the giant order pilasters appear as two-storeys tall, linking floors in a single unit.
A pilaster in civil engineering is a vertical rectangular member that is structurally a pier, and architecturally a column. Pilasters are used to decrease the slenderness ratio for the height of masonry walls - L/R<120.
Notes
^ Wittkower, Architectural Principles in the Age of Humanism (1962) 1965:36.
^ A useful phrase to identify a section of pilaster without a capital, with only its fluting to identify its relation to a column, is "pilaster strip".
^Mark Jarzombek, “Pilaster Play” Thresholds 28 Concerto Barocco, Essays dedicated to Henry Millon (Winter 2005), 34-41.
Lewis, Philippa and Gillian Darley, Dictionary of Ornament (1986) NY: Pantheon
