How many measurements can be less than the specified thickness when testing SFRM thickness on a joist?

In the context of testing the thickness of Spray-Applied Fire-Resistive Material (SFRM) on structural elements like joists, it is crucial to adhere to the specified thickness requirements outlined in building codes and manufacturer guidelines. The standard practice allows for a certain degree of variability in measurements to account for factors such as application inconsistencies and surface irregularities.

When determining the acceptable number of measurements that can be less than the specified thickness, guidelines typically indicate that only one measurement can be below the required thickness. This allowance recognizes potential minor application flaws while still maintaining the overall fire protection integrity provided by the SFRM. If more than one measurement falls below the specified thickness, it raises concerns regarding compliance and the material’s performance in a fire event.

Therefore, the understanding that only one measurement can be less than the specified thickness reflects a balance between practical application realities and the stringent safety regulations governing fire protection systems. This keeps structures safe while ensuring that inspection processes remain feasible and reasonable.