STUCCO – FINISHING MATERIAL
Stucco or render is a construction material made of aggregates, a binder, and water. Stucco is applied wet and hardens to a very dense solid. It is used as a decorative coating for walls and ceilings, exterior walls, and as a sculptural and artistic material in architecture. Stucco can be applied to construction materials such as metal, expanded metal lath, concrete, cinder block, or clay brick and adobe for decorative and structural purposes.
In English, “stucco” sometimes refers to a coating for the outside of a building and “plaster” to a coating for interiors; as described below, the material itself is often a little different. Other European languages, notably including Italian, do not have the same distinction; stucco means plaster in Italian and serves for both.
The basic composition of stucco is cement, water, and sand.
The difference in nomenclature between stucco, plaster, and mortar is based more on use than composition. Until the latter part of the nineteenth century, it was common that plaster, which was used inside a building, and stucco, which was used outside, would consist of the same primary materials: lime and sand (which are also used in mortar).
Traditional stucco is made of lime, sand, and water. Modern stucco is made of Portland cement, sand, and water. Lime is added to increase the permeability and workability of modern stucco. Sometimes additives such as acrylics and glass fibers are added to improve the structural properties of the stucco. This is usually done with what is considered a one-coat stucco system, as opposed to the traditional three-coat method.
But due to its brittle nature, stucco siding will crack if a house foundation settles. It simply isn’t the best choice in regions where the soil is high in clay, notorious for swelling and causing foundations to shift. Over time, even stucco on homes with firm foundations can develop hairline cracks.
