INSTALLING LATH AND PLASTER WALLS CODE

Traditional lath and plaster (including rock and metal lath varieties) has superior sound-proofing qualities when used with lime or gypsum plaster, which is denser than modern drywall. Wire mesh, often used for exterior stucco, is also found in combination or replacement of lath and plaster which serves similar purpose. For instance, building a rounded wall would be difficult if drywall were used exclusively, as drywall is not flexible enough to allow tight radii. One continued advantage of using traditional lath is for ornamental or unusual shapes. Traditional lime based plasters are resistant to moisture and provide excellent sound isolation. Drywall possesses poor sound dampening qualities and can be easily damaged by moisture. Lath and plaster methods have mostly been replaced with modern drywall or plasterboard, which is faster and less expensive to install. By the late 1930s, rock lath was the primary method used in residential plastering.

INSTALLING LATH AND PLASTER WALLS CODE

The purpose of the four-foot length is so that the sheet of lath exactly spans three interstud voids (overlapping half a stud at each end of a four-stud sequence in standard construction), the studs themselves being spaced 16 inches (410 mm) apart on center (United States building code standard measurements). Rock lath was typically produced in sheets sized 2 by 4 feet (610 by 1,220 mm). In use as early as 1900, rock lath (also known as 'button board,' 'plaster board' or 'gypsum-board lath'), is a type of gypsum wall board (essentially an early form of drywall) with holes spaced regularly to provide a 'key' for wet plaster. Sometimes, the mesh was dimpled to be self- furring. Metal lathing was spaced across a 13.5-inch (340 mm) center, attached by tie wires using lathers' nippers. Metal lath is categorized according to weight, type of ribbing, and whether the lath is galvanized or not. In addition to wood lath, various types of metal lath began to be used toward the end of the 19th century. Traditional lime based mortar/plaster often incorporates horsehair which reinforces the plasterwork, thereby helping to prevent the keys from breaking away. In this article's photo ('lath seen from the back.') the curls of plaster are called keys and are necessary to keep the plaster on the lath. After the plaster is completely dry, the walls are ready to be painted. A smooth, white finish coat goes on last. In three coat plastering it is standard to apply a second layer in the same fashion, leaving about 1⁄ 2 inch (13 mm) of rough, sandy plaster (called a brown coat or browning (UK)). When the wall is fully covered, the vertical lath 'guides' are removed, and their 'slots' are filled in, leaving a fairly uniform undercoat. A helper feeds new plaster onto the board, as the plaster is applied in quantity.

The applier drags the board upward over the wall, forcing the plaster into the gaps between the lath and leaving a layer on the front the depth of the temporary guides, typically about 1⁄ 4 inch (6.4 mm). Lime or gypsum plaster is then applied, typically using a wooden board as the application tool. Temporary lath guides are then placed vertically to the wall, usually at the studs. As Americans and Canadians expanded west, saw mills were not always available to create neatly planed boards and the first crop of buildings in any new western or northern settlement would be put up with split beam lath. Splitting the timber along its grain greatly improved the laths' strength and durability. and Canada well into the second half of the 19th century. Early American examples featured split beam construction, as did examples put up in rural areas of the U.S. In Canada and the United States the laths were generally sawn, but in the United Kingdom and its colonies, riven or split hardwood laths of random lengths and sizes were often used. Metal lath is available in 27-inch (69 cm) by 8-foot (240 cm) sheets. Each horizontal course of lath is spaced about 3⁄ 8 inch (9.5 mm) away from its neighboring courses. Wood lath is typically about one inch (2.5 cm) wide by four feet (1.2 m) long by 1⁄ 4 inch (6 mm) thick. Each wall frame is covered in lath, tacked at the studs. These are narrow strips of wood, extruded metal, or split boards, nailed horizontally across the wall studs or ceiling joists. The wall or ceiling finishing process begins with wood or metal laths. ( March 2012) ( Learn how and when to remove this template message) Unsourced material may be challenged and removed.

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Installing lath and plaster walls