A platform panel or module is provided to construct a surface for a deck, floor, wall, ceiling, or roof. The panel or module comprises a decorative top layer integral with or joined to a structural, composite molded platform. Each platform panel or module has two complementary module-coupling sides that take advantage of the full width of each joist that supports the platform. Also, male and female connecting members are disposed along the module-coupling sides that enable one platform panel or module to be efficiently and positively interlocked with an adjacent panel or module. Each panel or module can be fastened on one side to a single joist while being secured on its opposite side to an adjoining panel or module. The panels or modules are also designed to cover over an entire joist substructure, including the beginning-of-sequence and end-of-sequence joists.