laths

Laths are thin, narrow strips of material used as a base or framework for plaster, stucco, or other wall finishes. Traditionally made from softwood such as pine, wooden laths are installed horizontally across wall studs, spaced to create a keyed surface for plaster to grip. The spaces between laths allow for ventilation and drainage and provide a mechanical key that helps plaster adhere and resist cracking.

In modern construction, metal lath is common. Expanded metal lath consists of a lattice of metal strips expanded to form a mesh that resists sagging and improves adhesion for plaster. Welded wire lath and other metal laths serve similar purposes and are typically galvanized for corrosion resistance. Lath-and-plaster systems using wood or metal lath were widespread from the 18th through the mid-20th century; drywall has largely replaced these methods in new buildings, though plaster-on-metal-lath remains in restoration work and in certain regional practices.

Laths also appear in specialized plaster systems, such as plaster backer lath in veneer plaster applications or tile lath used to provide a stable backing for tile in wet areas. In general construction terms, a lath refers to any thin strip or strip-like reinforcement used to support a surface or finish.

In summary, laths provide a foundational grid or backing that helps plaster or other finishes adhere, cure correctly, and maintain structural integrity, with wood and metal varieties serving different historical and performance needs.