What is one role of metal lath in plastering?

• A. It decorates the wall
• B. It provides a strong backing, keys the plaster, and distributes weight to resist cracking
• C. It eliminates the need for bonding
• D. It finishes the surface

Answer: (B)

Metal lath provides a mechanical base for plaster, giving it something to grip onto. The rough, interlocking surface created by expanded or woven lath lets the plaster key in and adhere firmly, forming a strong backing. This backing also helps distribute any loads or movement across the plaster, reducing stress concentrations and resisting cracking as the wall experiences shrinkage, temperature changes, or substrate movement. Because of this combination, metal lath is embedded in the plaster coat to anchor and reinforce the system. It isn’t used for decoration, it doesn’t replace bonding, and it isn’t a finishing surface—the lath’s job is to back and key the plaster and help it stay intact under stress.