4841 Exterior timber stairs and ramps (0) Discrete primary circulation stairs and ramps, largely of timber, spanning between levels or part levels. May include integrated landings. Does not include stairs or ramps fabricated in place from normal structural timber framing. 4842 Exterior miscellaneous stairs and ramps (0) Discrete primary circulation stairs and ramps, of mixed or single materials, spanning between levels or part levels. May include integrated landings. Does not include stairs or ramps fabricated largely from timber, metal or concrete. 4843 Exterior metal stairs and ramps (1) Discrete primary circulation stairs and ramps, of mixed or single materials, spanning between levels or part levels. May include integrated landings. Does not include stairs or ramps fabricated largely from timber, or concrete. Includes custom made and modular systems with accessories. 4845 Exterior timber walkways and platforms (0) Discrete primary walkways and platforms, largely of timber, spanning (bridging) between separated parts of the same level or extending from a level. Does not include walkways and platforms fabricated in place from normal structural timber framing. 4846 Exterior miscellaneous walkways and platforms (0) Discrete primary walkways and platforms, of mixed or single materials, spanning (bridging) between separated parts of the same level or extending from a level. Does not include walkways and platforms fabricated largely from timber, metal or concrete.