Welded-wire fabric lath for interior surfaces and protected horizontal exterior surfaces must be fabricated from wire at least No. __ gauge.

Welded-wire fabric lath for interior surfaces and protected horizontal exterior surfaces must be fabricated from wire at least No. __ gauge.

• A. 14
• B. 16
• C. 18
• D. 20

Answer: (B)

Welded-wire fabric lath needs enough stiffness to provide a solid backing and a good plaster key. For interior surfaces and protected horizontal exterior surfaces, the lath must resist bending as plaster is applied and as the wall settles, so the plaster remains bonded and crack-free. Using wire of 16 gauge gives that necessary rigidity without being excessive. Thinner gauges (like 18 or 20) tend to flex or sag during plastering, compromising the key and increasing the risk of cracking or loose plaster. A thicker gauge (such as 14) would work, but 16 gauge is the minimum that reliably meets the strength needs for these surfaces while keeping cost reasonable.

Welded-wire fabric lath needs enough stiffness to provide a solid backing and a good plaster key. For interior surfaces and protected horizontal exterior surfaces, the lath must resist bending as plaster is applied and as the wall settles, so the plaster remains bonded and crack-free. Using wire of 16 gauge gives that necessary rigidity without being excessive. Thinner gauges (like 18 or 20) tend to flex or sag during plastering, compromising the key and increasing the risk of cracking or loose plaster. A thicker gauge (such as 14) would work, but 16 gauge is the minimum that reliably meets the strength needs for these surfaces while keeping cost reasonable.