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. Please help improve this section by adding citations to reliable sources.

Are lath and plaster walls load bearing