ASTM C1860-21 PDF Download

ASTM C1860-21 standard provides procedures for determining the tensile strength or bond strength of portland cement-based plaster. The purpose of these test methods is to assess the load capacities of the plaster installation, although the values obtained may not represent the actual wind load capacity or other structural properties. Therefore, the results must be interpreted based on engineering practice, relevant building regulations, and codes. The decision to use load results directly or with a safety factor for acceptable working loads is left to the test specifier's discretion, and the determination of an appropriate safety factor is also left to their discretion. The standard also emphasizes the need for sufficient test sampling when applying the test results from test specimens installed on existing structures to a larger wall area.

The test methods described in the standard are suitable for both new and existing construction and should be conducted at least 28 days after the application of the portland cement-based plaster. The destructive nature of the test procedures requires appropriate repair of the finish system and any underlying materials damaged during testing. The test methods differ based on the type of plaster installation, whether it is direct-applied or installed over mechanically attached lath. It also notes that no correlation should be made between laboratory and field testing. Furthermore, the standard clarifies that the test methods are not intended to evaluate the performance of the underlying construction or framing members, nor the coatings applied to the surface of the plaster. Instead, they serve as a tool for quantitatively evaluating existing portland cement plaster cladding that may have questionable bond or uncertain fastening to the substrate.