Cast stone is used as a masonry product to provide architectural trim, ornamentation or functional features on buildings and other structures.

The earliest known use of Cast Stone was in the year 1138. The product was first used extensively in London in 1900 and in America around 1920. The Cast Stone Institute was incorporated in 1927.

Since the early 1920's, Cast Stone has earned widespread acceptance in the architectural community as a suitable replacement for many masonry materials and for all types of natural cut building stone.

The manufacture of Cast Stone is generally regarded as the most labor-intensive of all concrete products' manufacturing processes. Of paramount importance to any Cast Stone manufacturer is the competence of his or her drafting department. In order to assure the success of the project, the detailer assigned to a Cast Stone job has both knowledge and experience. He or she must have knowledge of architectural styles and design and the individual must have experience in the manufacturing methods and the setting techniques employed by the mason contractor.

Since most other building products are either more "standardized" in nature (e.g. brick or window units) or less visible (e.g. structural steel) the Cast Stone usually becomes the custom element of the building facade which makes other materials fit together. The manufacturer details each piece with an aim toward simplification, each stone an architectural feat in itself.

The pattern or mold shop is the heart of any Cast Stone producer's enterprise because of the extraordinary degree of craftsmanship required. The most successful producers have been in the business for many years and thus are able to cultivate such talent.

Patterns for Cast Stone can be made from almost any material. The most common are wood, plaster, fiberglass and rubber. Other materials used are clay, geletin, gypsum, styrofoam, plastic, concrete and one of the earliest casting mediums, sand. Many advances have been made in rubber which have provided some very durable polyurethanes and polysulfides which are suitable for not only casting final products, but for obtaining impressions of existing and historical work as well.

The journeyman pattern maker knows which material to select for a given application and exactly how to use it. Model maker, mold maker, artist, sculptor, plasterer, master craftsman, and leader of men, the modern Cast Stoneplant's pattern shop foreperson must be all.

The two most widely-used casting methods today are the "Vibrant Dry Tamp" (VDT) system and the "Wet Cast" method. Each method requires a meticulously proportioned mix design consisting of carefully graded and washed natural gravel and sand, combined with crushed graded stone such as granite, marble, quartz or limestone meeting the lastest requirements of ASTM C 33.

The mixtures are proportioned for maximum density and to produce the required "fine grain texture similar to natural stone with no bug-holes permitted", while portland cement (ASTM C 150) is usually used to achieve lighter colors and color consistency. Blending of grey portland cement and coloring pigments (ASTM C 979), together with the white cement in order to achieve color is a fairly common practice.

Since a rich cement/aggregate ration of 1:3 is normally used, a properly (warm-moist) cured Cast Stone unit will have a somewhat higher compressive strength (6500 psi or higher, as tested by ASTM 1194) and a lower cold water absorption rate (6% or lower as tested by ASTM 1195) than natural limestone or normal concrete. The VDT method , due to it's inherently lower water/cement ratio, typically yields higher compressive strengths than low-slump concrete.

The VDT production system entails the vibratory ramming damp, zero-slump concrete against a rigid framework until it is densely compacted and ready for immediate removal from the form. This proccess enables as many as 100 pieces to be cast from a single mold in an eight-hour day and is ideally suited to fast-track construction projects due to its production capability and low form work requirements. The VDT process guarantees total absence of bug-holes and a finish which is difficult to distinguish from natural stone. The limitation of the process is that it generally requires one flat, unexposed side to the design.

Sandblast or chemical retardation finishing methods (normally used in the finishing of architectural precast concrete panels) are seldom used with Cast Stone because of the dulling of aggregates and the loss of fine detail which are not acceptable in quality Cast Stone work. Cost per unit depends greatly on individual component design, component repetition, specification and bid documents. On average, however, Cast Stone costs less than quarried stone. There are several reasons. One is that it is a molded product and requires no further tooling after the initial pattern is made. Each piece of cut stone must be hauled over long distances. Most of the limestone in this country is hauled from Indiana. Many stones come from overseas. Brownstone is now typically available from one main source, Germany. Cast Stone is a highly versatile architectural precast building material which looks like, is usually stronger than, weathers better, has greater color consistency, can be reinforced, and costs less than natural cut stone.