Lath

A lath or slat is a thin, narrow strip of straight-grained wood used under roof shingles or tiles, on lath and plaster walls and ceilings to hold plaster, and in lattice and trellis work.^[1]

Lath has expanded to mean any type of backing material for plaster. This includes metal wire mesh or expanded metal that is applied to a wood or metal framework as matrix over which stucco or plaster is applied, as well as drywall products called gypsum or rock lath.^[2] Historically, reed mat was also used as a lath material.

One of the key elements of lath, whether wooden slats or wire mesh, are the openings or gaps that allow plaster or stucco to ooze behind and form a mechanical bond to the lath. This is not necessary for gypsum lath, which relies on a chemical bond.^[2]