Gypsum lath is similar to gypsumboard in that it consists of a core of set gypsum surfaced with paper. The paper for gypsumboard, however, is produced so that it is ready to receive paint or paper, while that for gypsum lath is specially designed or treated so that plaster will bond tightly to the paper. In addition, some lath provides perforations or other mechanical keying to assist in holding the plaster firmly on the lath. It is also available with reflective foil backing (see also Art. 11.25.5).
Gypsum lath should conform with ASTM C37. It comes in 16-, 161â„2-, 24-, and 32-in widths, lengths of 32, 36, and 48 in, and 3â„8- and 1â„2-in widths.
Veneers plasters, special proprietary compositions for thin plaster surfaces, are best applied over veneer plaster base, similar to gypsum lath, but produced to accommodate the veneer plaster compositions. Both gypsum lath and veneer base are made as regular, X-rated (fire-retardant), and insulating (foil-backed) types.
These bases should conform with ASTM G588. They come 48 in wide, 6 to 16 ft long, and 3â„8, 1â„2, and 5â„8 in thick.
