What can be used instead of metal lath to create a mechanical break between SFRM and the substrate?

• A. Wood blocking
• B. Fiberglass mesh
• C. 12-gauge steel studs
• D. Aluminum channels

Answer: (C)

The main idea here is to create a nonbonded break between the sprayed fireproofing and the substrate, so the coating can move independently and crack control is improved. A 12-gauge steel stud backing provides a solid, noncombustible break plane between the substrate and the SFRM. It’s rigid, predictable, and designed to withstand fire exposure without degrading, so it maintains the separation needed for the coating to perform properly.

Wood blocking would be combustible and unreliable in a fire-rated assembly. Fiberglass mesh is typically used inside the coating to reinforce it, not as a dedicated break plane. Aluminum channels can act as a furring system, but they don’t offer the same combination of strength, stability, and noncombustibility as steel studs.