Gibbs surround

A Gibbs surround or Gibbs Surround is a type of architectural frame surrounding a door, window or niche in the tradition of classical architecture. The formula is not fixed, but several of the following elements will be found. The door is surrounded by an architrave, or perhaps consists of or is flanked by pilasters or columns. These are with "blocking", where rectangular blocks stick out at intervals, usually alternating to represent half the surround. Above the opening there are large rusticated voussoirs and a keystone and a pediment above that. The most essential element is the alternation of blocking with non-blocking elements. Some definitions extend to including arches or square openings merely with alternate blocked elements that continue round the top in the same manner as the sides, as in the rectangular windows of the White House's north front basement level.

Though intended for masonry in stone, the motif can be executed in other materials, especially brick, often masked in stucco, wood, or just paint. British vernacular housing of the late 19th century often uses alternating coloured blocks, with little or no projection from the main wall plane, but emphasized by a different colour from the main wall. These can be seen even on small terraced houses, often using cast stone, and used on both the door and ground floor windows.

It is named after the architect James Gibbs, who often used it and popularized it in England, for example at St Martin-in-the-Fields, London. Here the side doors have surrounds with all the details including pediments, while the round-topped windows along the sides have Gibbs surrounds if the broadest definition is used. However, Gibbs certainly did not invent it. The formula can be found in Ancient Roman architecture, and became popular in Renaissance architecture from the early 16th century. Gibbs illustrated a version in his pattern-book A Book of Architecture (1728), though there the blocking stopped at the edge of the architrave. More often the blocking overlies it. This was swiftly plagiarized by rival books such as William Salmon's Palladio Londinensis (1734), which credits Andrea Palladio (d. 1580) with the origin of what Salmon calls a "Rustick Window and door".

...
Wikipedia