Modern stucco is used as an exterior cement plaster wall covering. It is usually a mix of sand, Portland cement, lime and water, but may also consist of a proprietary mix of additives including fibers and synthetic acrylics that add strength and flexibility. Modern synthetic stucco can be applied as one base layer and a finish layer, which is thinner and faster to apply, compared to the traditional application of three-coat stucco. Imitation stone stucco can also be produced using the traditional application, but with marble dust being added to the mixture.
Applying stuccoAs with any cement-based material, stucco must be reinforced to resist movement cracking. Plastic or wire mesh lath, attached with nails or screws to the structural framing, is embedded into the base coat to provide stiffening for the stucco.
Where stucco is to be applied to a structure of wood-framing or light-gauge steel framing, the framing is protected from moisture damage by applying a cement based primer, or a vapor-permeable, water-resistant weather barrier; typically an asphalt-saturated paper or one of a variety of manufactured plastic-based sheets, known as building wraps or stucco wraps. The properties of the weather barrier must not only protect the framing from rain and moisture, but at the same time allow the free passage of any water vapor generated inside the building to escape through the wall.
A wide variety of stucco accessories, such as weep screeds, control and expansion joints, corner-aids and architectural reveals are sometimes also incorporated into the lath. Wire lath is used to give the plaster something to attach to and to add strength. Types include expanded-metal lath, woven-wire lath, and welded-wire lath.
