Stucco siding is a mixture of cement, sand and lime that is placed on the exterior walls of houses and buildings. Stucco is an exterior siding that is durable, weather-resistant and attractive. It is a heavy substance that holds up well in wet weather because it is porous and can absorb moisture, and it will dry easily without damage. Pigments can be added to the stucco siding to create a wide variety of colors, and it will never need to be painted. Stucco siding is typically found on Spanish, Mediterranean and mission-style homes and buildings.
The stucco siding process starts with wooden walls that are covered in tar paper and then galvanized metal screening or chicken wire. The metal is then covered in three layers of stucco. The tar paper protects the wood framing of the house from the moisture that can pass through the stucco. The metal screening gives the stucco something to attach to and provides additional strength.
The first layer of stucco siding is called the scratch coat. A brush is used to make scratches in the surface, usually in a crisscross or horizontal pattern. This layer must dry completely before the second layer is applied.
The next layer is the brown coat or leveling coat that is leveled and scraped smooth and allowed to dry for a week to 10 days to allow for cracking and shrinking. If the weather is very dry, the layers of stucco will be sprayed with water to keep from drying too soon and becoming brittle.
The final layer is called the finish coat and can be one of two types. A color coat is colored with pigments and can be textured. An acrylic finish is acrylic-based, is thinner than a color coat and is used for long-lasting quality.
During the Renaissance, stucco techniques were used by the Italians, and then use of the process spread throughout Europe. At that time, the stucco substance previously used by ancient Romans and Greeks to paint on — a fine-grained plaster made of marble dust, glue and gypsum — was molded into decorative shapes, then polished until shiny or painted. As the decades continued on, the ingredients of stucco siding evolved, and it came to be used on the exterior of houses for protection from the elements. Stucco siding has continued to evolve, and synthetic products are now available.