|
INTRODUCTION
Simply stated, a cavity wall is two wythes of masonry, separated by a cavity of varying dimension. The masonry wythes may consist of
solid brick, structural clay tile, or concrete masonry units and are bonded together with masonry ties. The cavity (ranging from 2 inches to 4 1/2 inches in width) may or may not contain insulation. See Figure 1.
Combining these elements with a sound structural design, appropriate details, quality materials and good workmanship will result in high performance cavity walls.
HISTORY
Cavity walls are not new, they have been observed in ancient Greek and Roman structures. At the Greco Roman town of Pergamum, on the
hills overlooking the Turkish town of Bergama, a stone wall of cavity type construction still exists. Sometime in the early part of the 19th century, the cavity wall was probably reinvented by the British.
Plans dating as early as 1805 suggest a type of construction, featuring two leaves of brickwork, bonded by headers spanning across a 6-inch cavity. An early British publication (dated 1821) suggests the use of
cavity walls as a means of protection against moisture penetration. The use of metal ties was introduced in Southern England sometime after 1850. These original ties were made of wrought iron.
Cavity walls were first built in the United States late in the 19th century. Figure 2 illustrates an alternate type of cavity wall
system originally featured in an 1899 text book assembled for people engaged in the engineering professions and construction trades. However, it was not until 1937 that this type of construction gained official
acceptance by any building or construction agency in the United States. Since then, interest in and use of cavity walls in this country has increased rapidly. This has resulted in extensive testing to determine
cavity wall properties and performance.
The early use of cavity walls in this country was limited primarily to exterior load-bearing walls in low rise construction. In the
1940s, designers began to recognize the advantages of cavity walls in high-rise buildings. Today, masonry cavity walls are used extensively throughout the United States in all types of buildings. The primary reasons
for their popularity are superior resistance to rain penetration, excellent thermal properties, excellent resistance to sound transmission and high resistance to fire.
|
