Plaster veneer
Plaster veneer (US terminology) or plaster skim (UK terminology) is a construction methodology for surfacing interior walls, by applying a thin layer of plaster over a substrate—typically over specially formulated gypsum board base, similar in nature to drywall. History. Until the mid twentieth century, it was standard practice in Western construction to surface interior walls using wooden lath and a layer of plaster about a half-inch thick ("lath and plaster"). Later, drywall became a standard. Typically, drywall is surfaced using the "mud-and-tape" method, where non-adhesive paper or mesh tape and drywall Joint compound  ("mud") is used to fill joints, cover nail heads, and repair any flaws. Plaster veneer was developed as a way of taking advantage of the reduced labor of modern drywall, while providing a genuine plaster surface for a wall. Applications. In much of the world, plaster veneer is a very rare wall surface. Consequently, it can be difficult to find a local trade worker skilled in the practice. However, in some regions, such as Ireland, or Massachusetts this situation is reversed, with plaster veneer a common standard, and mud-and-tape the less common alternative. Bare mud-and-tape drywall  is generally only acceptable as a final decorating finish in utility spaces such as attics or garages. In most rooms, such walls are finished with paint or wallpaper. Plaster veneer walls are usually similarly decorated, but unpainted plaster can also serve as a finish. Because bare plaster can be appealing to the touch, and paint would add an additional layer, some decorators opt to leave exposed plaster in some or all of a room, as a creative choice. In such cases, if the plaster's natural color is not desired, tints can be added as part of the mixing process , or can be introduced unevenly for artistic color effects. Methodology. The plaster veneer method begins with the hanging of specially designated drywall ("blueboard"), in the conventional manner., N.B. In North America, the color of the face paper of drywall indicates its intended application: white for standard, green for moisture resistance, etc. Plaster veneer wallboard is blue or gray . Plaster veneer may also be applied to ordinary drywall, or over existing walls, but this requires "gluing" the existing wall surface by painting on a special adhesive compound, and then applying a thin layer of "base coat" plaster. After the blueboard or  base coat covers the interior of a room, the finishing plaster is mixed in batches (typically about 5 gallons), by blending plaster powder with water, to the ideal consistency. Working quickly, a thin layer (usually one to three millimeters) of finish plaster is applied over a wall face before the plaster begins to congeal in the bucket. Over a period of a few hours, as the plaster chemically sets on the wall, it is periodically smoothed or textured using hand trowels, until the desired finish is achieved. When a wall face has sufficiently set, an adjoining face can be safely  applied. After the plaster has fully set, it is allowed to cure for a period of days to weeks, permitting excess moisture to escape into the air. If the plaster is no more than about three millimeters thick, two to three days' cure time is usually sufficient. A skilled eye can see areas where moisture is lingering until the curing is complete. After the walls are fully cured, they are ideal for painting or papering. Advantages of plaster veneer. Some considerations favor plaster veneer over mud-and-tape drywall. Disadvantages of plaster veneer. Some considerations make plaster veneer a less  appropriate choice than mud-and-tape drywall.