Stucco

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Stucco is a material made of an aggregate, a binder, and water which is applied to a surface in a paste-like consistency when wet and when dry becomes hard. Also used in sidings, it is used as a coating for walls and ceilings or for decoration. In Europe the term render is more commonly used. Stucco may be used to cover less visually appealing construction materials such as concrete blocks, steel, adobe, or JB Weld.

The difference in nomenclature between stucco, plaster, and mortar is based more on use than composition. Until the later part of the nineteenth century, it was common to have plaster, which was used inside the building, and stucco, which was used outside the building, consist of the same primary materials: lime and sand (lime and sand are also used in mortar). Animal or plant fibers were often added for additional tensile strength. In the later part of the nineteenth century, Portland cement began to be added with increasing frequency to stucco in an attempt to improve its durability. At the same time, traditional lime plasters were being replaced by gypsum plaster.

Traditional stucco is made of lime, sand, and water. Modern stucco is made of Portland cement and water. Lime is often 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 plaster as well as its workability. This is usually done with what is considered a "one coat" stucco system—as opposed to the traditional 3 coat method.

Lime stucco is a relatively hard material that can be broken or chipped by hand without too much difficulty. The lime itself is usually white; color comes from the aggregate or any added pigments. Lime stucco has the property of being self-healing to a limited degree due to the slight solubility of lime (lime in solution can be deposited in cracks where it later solidifies). Portland cement stucco is very hard and brittle and can easily crack if the base on which it is applied is not stable. Typically its color is gray due to the innate color of most Portland cement (white Portland cement is also used).

Traditionally stucco was directly applied to a masonry surface such as brick or stone. In wood-framed buildings, stucco was applied over wood lath. Modern stucco is usually applied over an expanded metal lath that is fastened to the wall sheathing with staples, with a 2 layer moisture barrier in between.

Traditionally, stucco has been used as a sculptural and artistic material. Baroque and Rococo architecture makes heavy use of stucco. Examples can be found in churches and palaces, where stucco is mostly used to provide a smooth, decorative transition from walls to ceiling, decorating and giving measure to ceiling surfaces. Stucco is an integral part of the art of belcomposto, the baroque concept that smoothly integrates the three classic arts, architecture, sculpture, and painting.

Since stucco can be used as a decorative means, but also for figurative representation, it provides an ideal transitive link from architectural details to wall paintings such as the typically baroque trompe l'oeil ceilings. Here, the real architecture of the church is visually extended into a heavenly architecture with a depiction of Christ, the Virgin Mary or the Last Judgment at the center. Stucco is being used to form a semi-plastic extension of the real architecture that merges into the painted architecture.

Islamic art makes use of stucco as a decorative means in mosques and palaces. Indian architecture knows stucco as a material for sculpture in an architectural context.

Due to its "aristocratic" look, baroque looking stucco decoration was used frequently in upper-class apartments of the 19th and early 20th century.

It was also employed in the 1950's in pre-molded forms for decorating the joins between walls and ceilings inside houses. It was generally painted the same colour as the ceiling and used in designs where a picture rail or rat rail was in use.

Modern Stucco consists of 1 layer of wire lath and 3 layers of portland cement based plaster. When applied to metal lath, three coats of portland cement plaster form a 7/8-inch total thickness. Portland cement plaster has high impact resistance, sheds water, but breathes, allowing water vapor to escape.

1st a Wire Mesh is attached to vapor permeable, water-resistant "tar" paper. The paper protects the sheathing and interior of the wall from outside moisture intrusion without trapping moisture vapor in the wall. Wire lath is used to give the cement something to attach to and may be expanded-metal lath, woven-wire lath, or welded-wire lath.

Then a layer which is composed of Portland Cement and sand called scratch coat is applied. A "comb" is used to scratch the surface horizontally or in a criss cross pattern to provide a surface which the next layer can hang from.

The next layer is called Brown coat. It consists of Portland Cement, Mortar, and sand. It is trowelled on to provide the surface with texture.

The next layer is called color coat and consists of cement, sand, coloring agents(mineral oxide pigments), and glue(adhesive used to make it stick to the brown coat).

Lime is often used in the mixture depending on the textured finish desired and the climate of the area.

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