POST-AND-LINTEL

   The earliest, simplest method for spanning a space is the post-and-lintel system of upright posts to support a horizontal beam, called a lintel. The width of the lintel is limited not only by its tensile strength, but also by the length of the materials possible for use as a lintel. Often, a series of posts must be used to increase the overall width of an enclosed space, creating a room encumbered by columns or wall divisions. Although most structures employ a post-and-lintel system, one of the more famous examples of the use of a post-and-lintel is Stonehenge, constructed in the Salisbury Plain of Wiltshire, England, around 2750 BC. Here, five pairs of vertical megaliths called trilithons are formed in the shape of a horseshoe, and each pair was capped by a lintel. This group was surrounded by an outer circle of megaliths capped by a continuous lintel of massive horizontal stones. Other Prehistoric structures include individual freestanding post-and-lintel stone formations found across Europe, called dolmens.

   Stone post-and-lintel structures are found throughout the Ancient Near East and Ancient Egypt, while wood was also used through-out Europe in post-and-lintel construction. By the 18th century, the replacement of stone and wood lintels by cast-iron and then steel frames has allowed for a gradual increase in unobstructed room widths that rival the size of domed interiors, yet with flat roofs and broad interiors supported by metal framing.