1.1 This specification covers the procedures to establish a performance rating for wood-plastic composite (WPC) deck boards. This specification also defines the procedures to establish a performance rating for WPC guards and handrails. The purpose of this specification is to establish the basis for code recognition of these products or systems in exterior applications where combustible construction is allowed (see X1.1).

Note 1 - While WPCs may contain wood fiber, the presence of wood fiber in the composite is not required by this standard. Other lignocellulosic materials may be used. For WPC deck boards and guardrail systems evaluated according to this standard, the structural, physical, and fire attributes may or may not exhibit similarity to those of wood due to the presence, type, and quantity of plastic(s) in the composite. WPCs should not be assumed to behave similarly to wood. For example, to address the influence of plastic in the composite, special considerations in the standard address sensitivity to temperature, ultraviolet (UV) exposure, and freeze-thaw resistance.

1.2 Deck boards, guards, and handrails covered by this specification are permitted to be of any code compliant shape and thickness (solid or non-solid).

Note 2 - While WPCs are produced in a broad range of ratios of fiber to resin it is recognized that the performance requirements in this specification are valid for any material or combination of materials used as deck boards, guards, or handrails. For products made primarily from resin, or for products that exhibit highly plastic properties (for example, more than 3 % strain without rupture in a standard flexural test under ambient conditions), users are directed to Specification D6662 for additional guidance.

1.3 A deck board, and a deck board used as a stair tread, are assigned a span rating indicating its ability to comply with model code specified functions identified for its specific end use. A guard or handrail is recognized for its ability to meet minimum code requirements specified in the appropriate model building code.

1.4 Details of manufacturing processes may be proprietary and are beyond the scope of this specification.