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A wall is a usually solid structure that defines and sometimes protects space. Most commonly, a wall separates
space in buildings into rooms, or protects or delineates a space in the open air. There are
three principal types of structural walls: building walls, exterior boundary walls, and retaining walls.
Stone wall of an English barn
Building walls have two main purposes: to support roofs and ceilings, and to divide space, providing security against
intrusion and weather. Such walls most often have three or more separate components. In today's construction, a building wall
will usually have the structural elements (such as 2×4 studs in a house wall), insulation, and finish elements, or surface (such as drywall or
paneling). In addition, the wall may
house various types of electrical wiring or plumbing. Electrical outlets are usually mounted in walls. Building walls frequently become
works of art, such as when murals are painted on them.
Boundary walls include privacy walls, boundary-marking walls, and city walls. These intergrade into fences; the conventional differentiation is that a fence is of minimal thickness and often is open in nature,
while a wall is usually more than a nominal thickness and is completely closed, or opaque. More to the point, if an exterior
structure is made of wood or wire, it is generally referred to as a fence, while if it is made of masonry, it is considered a
wall. A common term for both is barrier, convenient if it is partly a wall and partly a fence, e.g. the Israeli West Bank barrier.
Before the invention of artillery, many European cities had protective
walls. Since they are no longer relevant for defense, the cities have grown beyond their walls, and many of the walls have
been torn down. Extreme examples of boundary walls include the Great Wall of China and Hadrian's Wall.
In areas of rocky soils around the world, farmers (and their slaves, as in the southern United States) have often pulled large quantities of stone out of their fields to make farming easier, and
have stacked those stones to make walls that either mark the field boundary, or the property boundary, or both.
Retaining walls are a special type of wall, that may be either
external to a building or part of a building, that serves to provide a barrier to the movement of earth, stone or water. The
ground surface or water on one side of a retaining wall will be noticeably higher than on the other side. A dike (construction) is one type of retaining wall, as is a
levee.
The term "the Wall" frequently referred to the Berlin
Wall, erected during the Cold War, which fell in 1989.
See also
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