Wood patio decks are outdoor living spaces that are built above ground. While they typically adjoin a structure, such as a home, they can also be built as a boardwalk or be atop a building as an observation deck. The structure of a wood patio deck is commonly framed with treated lumber. While a number of different types of wood, including softwood, hardwood, domestic or tropical wood, can be used for the top surface deck, each has it's own advantages and disadvantages.