When metal lath is used for SFRM application, it must weigh at least:

When using metal lath for Spray-Applied Fire-Resistive Material (SFRM) application, it is crucial that the lath meets specific weight requirements to ensure proper structural support and effectiveness of the fireproofing system. The requirement for the metal lath to weigh at least 1.7 lb/cubic yard is based on industry standards that ensure the lath provides adequate mechanical strength and surface area for the spray-applied fireproofing material to adhere effectively.

This weight specification is important because a heavier lath typically offers better support for the SFRM, preventing issues such as sagging or detachment over time, which can compromise fire resistance. The correct weight helps in achieving a proper bond between the lath and the fireproofing material, ensuring that the fire protection system functions as intended during a fire event. This also minimizes risks during installation and operation.

Thus, the choice of 1.7 lb/cubic yard is based on balancing the physical properties of the lath and the performance requirements of the fireproofing application, making it the most suitable option.