lathandplaster

Lath and plaster is a traditional wall and ceiling construction method in which a framework of lath is covered with plaster. The lath serves as a keying surface for the plaster and helps transfer loads to the structural studs. This technique was widely used in Europe and North America from the 17th through the mid-20th century, and variations persist in older buildings today.

Lath can be wood or metal. Wood lath consists of slim strips nailed horizontally to studs with narrow gaps between them, creating channels for the plaster to grip. Metal lath, including expanded metal or mesh types, provides a rigid, continuous substrate and became popular in the late 19th and early 20th centuries. Plaster used with lath was traditionally lime-based, often containing horsehair to improve tensile strength and reduce cracking; later gypsum-based plasters were introduced.

A typical plaster system is applied in coats. The scratch coat is spread over the lath and scored to form a key. A brown coat builds thickness and strength, followed by a finish coat that provides a smooth surface. Common ratios and thicknesses vary, but the total plaster thickness is usually about a half to three-quarters of an inch, depending on the coat system and local practice.

Historically valued for its fire resistance, rigidity, and acoustical properties, lath and plaster declined with the rise of gypsum board (drywall) from the mid-20th century onward. In existing historic buildings, it remains prized for authenticity and can be repaired by matching traditional lime or gypsum plasters and restoring or replacing damaged lath where needed. Renovation may require careful assessment for moisture, structural movement, and, in older materials, potential hazards such as lead paint or asbestos-containing products.