Stone veneer that is 8 inches thick weighs 6 tons or more per 100 square feet. Stone veneers must be set on a solid masonry ledge built into the concrete footing, which means more concrete than for an unveneered foundation. Setting stone is labor-intensive, and skilled masons may not be as easy to find as carpenters who can install other types of siding.
Manufactured stone is lightweight concrete that has been molded and colored to look like building stone. It costs one-third to one-half as much as real stone veneer, and it’s light enough to adhere to a wall without any special footing for support.
Manufactured stone is made in a variety of colors and patterns but, unlike natural stone, the coloration is only on the surface, so cut edges must be concealed in the mortar joint.
Many unwary builders have been plagued by callbacks after installing natural or manufactured stone veneer over OSB sheathing. Installers typically apply wire lath over two layers of #30 felt and adhere the natural or manufactured stone to the wall with mortar. This installation method, however, has been associated with a rash of catastrophic failures, especially on walls with OSB sheathing. Unless a three-dimensional drainage mat or dimple mat is included between the two layers, little drainage may result.
Stone veneer and manufactured stone are reservoir claddings, meaning that they absorb and hold water after a rainstorm. Once the sun comes out, the wet cladding tries to dry in both directions, which can push moisture into the building, a process called inward solar vapor drive.
A well-detailed stone veneer installation requires vapor-impermeable sheathing to slow inward solar vapor drive. In most cases, extruded polystyrene or polyisocyanurate foam are the best sheathings to use under stone veneer. Vapor-permeable sheathings like Celotex should never be used…