Topic Summary
Manufactured stone is made by casting a mixture of portland cement, aggregate, and blended pigments in a large variety of molds. Molds are designed to simulate many varieties of natural stone, with limestone, fieldstone, ledgestone, and river rock being popular styles. Stone sizes can range from small, finger-sized pieces (1"x2") to large flat stones as big as 20" x 20." Corner pieces are carefully designed to provide the illusion of thicker, more traditional stone. Special shapes are also available, offering design flexibility for window and door surrounds, arches, cap stones, and other trim. The wide variety of styles and ease of installation make manufactured stone a realistic option for almost any exterior or interior surface. Among the typical exterior applications are veneered wall surfaces, columns, archways, and landscaping walls and fences. Interior applications of manufactured stone are typically veneered wall surfaces, fireplace veneers, and accent panels.
While manufactured stone can be used almost anywhere that natural stone could be used, the installation process is quite different. Manufactured stone is a veneer that is adhered directly to the backing substrate with a stucco scratch coat and mortar. Natural stone assemblies, like unit masonry, are constructed to bear upon the stones below. The adhesion or bonding of the stone units and the drainage of the exterior assemblies are the primary concerns in the detailing of a manufactured stone installation. The stucco coat and mortar used to bond the stones to the subsurface must achieve the proper chemical reaction to ensure a long-lasting bond. As the stones and mortar are still basically pourous materials, water can penetrate the assembly, making a drainage system necessary. Manufactured stone can be installed over substrates of plywood, board insulation, and cement board, which are covered with a layer of felt paper to prevent water from migrating into the substrate. Special felt papers are available with channels that allow moisture to drain to a weep system at the base of the assembly.
