Stucco

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, and as a sculptural and artistic material in architecture. Stucco may be used to cover less visually appealing construction materials, such as metal, concrete, cinder block, or clay brick and adobe.To obtain a neat repair, the area to be patched should be squared-off with a butt joint, using a cold chisel, a hatchet, a diamond blade saw, or a masonry bit. Sometimes it may be preferable to leave the area to be patched in an irregular shape which may result in a less conspicuous patch. Proper preparation of the area to be patched requires very sharp tools, and extreme caution on the part of the plasterer not to break keys of surrounding good stucco by 'over-sounding' when removing deteriorated stucco.After thoroughly dampening the masonry or wood lath, the first, scratch coat should be applied to the masonry substrate, or wood or metal lath, in a thickness that corresponds to the original if extant, or generally about 1/4' to 3/8'. The scratch coat should be scratched or crosshatched with a comb to provide a key to hold the second coat. It usually takes 24-72 hours, and longer in cold weather, for each coat to dry before the next coat can be applied. The second coat should be about the same thickness as the first, and the total thickness of the first two coats should generally not exceed about 5/8'. This second or leveling coat should be roughened using a wood float with a nail protruding to provide a key for the final or finish coat. The finish coat, about 1/4' thick, is applied after the previous coat has initially set. If this is not feasible, the base coat should be thoroughly dampened when the finish coat is applied later. The finish coat should be worked to match the texture of the original stucco. 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, and as a sculptural and artistic material in architecture. Stucco may be used to cover less visually appealing construction materials, such as metal, concrete, cinder block, or clay brick and adobe. In English, 'stucco' usually 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 little different. However, other European languages, notably including Italian, do not have the same distinction; stucco means plaster in Italian and serves for both. This has led to English-speakers sometimes using 'stucco' for interior decorative plasterwork in relief. 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). Animal or plant fibers were often added for additional strength. In the latter nineteenth century, Portland cement was added with increasing frequency in an attempt to improve the durability of stucco. 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, 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. 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 because of the slight water solubility of lime (which in solution can be deposited in cracks, where it 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 was gray, from the innate color of most Portland cement, but white Portland cement is also used. Today's stucco manufacturers offer a very wide range of colors that can be mixed integrally in the finish coat. Other materials such as stone and glass chips are sometimes 'dashed' onto the finish coat before drying, with the finished product commonly known as 'rock dash', 'pebble dash', or also as roughcast if the stones are incorporated directly into the stucco, used mainly from the early 20th through the early 21st Century. As a building material, stucco is a durable, attractive, and weather-resistant wall covering. It was traditionally used as both an interior and exterior finish applied in one or two thin layers directly over a solid masonry, brick, or stone surface. The finish coat usually contained an integral color and was typically textured for appearance. Then with the introduction and development of heavy timber and light wood-framed construction methods, stucco was adapted for this new use by adding a reinforcement lattice, or lath, attached to and spanning between the structural supports and by increasing the thickness and number of layers of the total system. The lath added support for the wet plaster and tensile strength to the brittle, cured stucco; while the increased thickness and number of layers helped control cracking.