Masonry Magazine December 2005 Page. 24
CAST STONE
Beginning in the 1950s, the sizes of architectural cladding units steadily increased until the concepts of masonry construction would no longer apply. Larger units, when integrated into cavity wall veneer systems, would face new obstacles dealing with the temperature, moisture, movement, volume changes and differentials of materials bonded together with mortar. With the weight restriction implicit in hand laying, shrinkage of individual masonry units is not so large as to create local debonding problems. Masons can place larger elements - such as precast concrete lintels or sills - but that placement is generally not governed by masonry specifications, and hence not within the jurisdiction of the Masonry Standards Joint Committee (MSJC) and other masonry associations.
Shop drawings for cast stone should be prepared by a qualified manufacturer to include details and sizes of stones, arrangement of joints, bonding, relationship with other materials, anchoring and proper location in the structure before the manufacturer should be allowed to proceed with the work.
For best practice, concrete manufactured to simulate natural stone used in masonry construction should be specified as cast stone under the CSI division 04 72 00. Larger units, not generally set by masons in a unit masonry application should be specified as architectural precast concrete under the CSI division 03 45 00.
Other Types of Simulated Stones
PROPERLY MANUFACTURED cast stone has the same or stronger physical properties as most natural dimensional building stone, and should not be confused with other types of simulated stones. Several companies manufacture proprietary stone, products that are used primarily as veneers on other substrate materials such as concrete masonry units. These products are manufactured to meet requirements for simulated stone - now under CSI Division 04 42 00, which covers various types of supported stone cladding.