ASTM C1325-22 PDF Download

The ASTM C1325-22 standard specifies the requirements for non-asbestos fiber-mat reinforced cementitious backer units. These units are designed to be dimensionally stable and can be used as an unfinished substrate or as a substrate for decoration in wet and dry areas. The standard categorizes the backer units into two types: Type A, which is suitable for exterior applications as a substrate for cladding materials or as an unfinished substrate for decoration, and Type B, which is intended for covered exterior applications or for interior wet or dry areas where dimensional stability is required.

The manufacturing process of these backer units can involve the use of pressure and curing under natural or accelerated conditions to meet the property requirements. When testing the mechanical and physical properties of the product, it is preferred to conduct the tests on uncoated units. The specification includes requirements for flexural strength, density, modulus of elasticity, and other properties that the backer units must meet.

It is important to note that this standard does not apply to asbestos-cement flat sheets, non-asbestos fiber cement flat sheets for exterior applications, gypsum boards, glass mat gypsum backing boards, particle boards, or discrete non-asbestos fiber cement interior substrate sheets. For proper application details when using the backer units as an unfinished substrate, it is recommended to consult the manufacturer's written installation literature.