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1.1 This specification covers non-asbestos fiber-mat reinforced cementitious backer units manufactured to be dimensionally stable and suitable as either an unfinished substrate (see Note 1) or as a substrate for decoration such as natural stone or tile on walls, floors, or decks in wet and dry areas. It is also suitable to be used as a substrate in the Application of Class PB Exterior Insulation Finish Systems (Practice C1397), the Application of Direct-Applied Finish Systems (Practice C1516), and the Application of Exterior Insulation Finish Systems Class PI (Practice C1535).

1.2 This specification is not applicable to asbestos-cement flat sheets (Specification C220); non-asbestos fiber cement flat sheets for exterior applications such as claddings, facades, curtain walls, and soffits (Specification C1186); gypsum backing board, coreboard, and shaftliner (Specification C1396/C1396M); water-resistant gypsum backing board (Specification C1396/C1396M); glass mat gypsum backing board (Specification C1178/C1178M); particle boards (Definitions D1554); and discrete non-asbestos fiber cement interior substrate sheets (Specification C1288).

1.3 Units—The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.

1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.