Special Inspector (SI) Certifications Fireproofing Practice Test

The test cap diameter is chosen to produce reliable, comparable bond strength measurements. A 2 to 3-1/4 inch cap strikes the right balance: it’s large enough to average out small surface irregularities and reduce edge concentration effects, but small enough to keep the required pull force within typical testing equipment and to minimize edge-related failures of the substrate. This standard-sized range ensures results are consistent across samples and projects, which is why it’s the allowable choice for SFRM bond strength testing.