Abstract: An interior space expansion system for use with a structure needing collapsible and/or expandable space, including: a base structure having an aperture therethrough; a movable structure disposed within a central region of the base structure when in a sunken position and substantially exterior the base structure when in an elevated position; and a lifting system coupled to the base structure and the movable structure. The base structure is a trailer or recreational vehicle. The movable structure includes a cab a carriage and a footing. The lifting system couples to the footing and transitions the movable structure between the sunken and elevated positions. The lifting system is not substantially disposed within the central region of the base structure when the movable structure is in the elevated position. There is a cap member for covering the aperture when the movable structure is in the sunken position.