A modular space system comprising load bearing components designed with graphics software, manufactured with data from the graphics software, and assembled onto building frames. A user enters dimensions, materials, and other design parameters to generate a graphic rendition and prepare components. Load bearing walls, a floor, and a ceiling are assembled into a stand alone unit that can be attached to a building frame directly, such that the walls, floor, and/or ceiling are flush with, or naturally interface with other surfaces of the building, such as plasterboard walls. The unit can also be attached to the frames through an existing surface and/or to the existing surface. Interfaces between load bearing surfaces are precise, reducing the need for finish work, such as taping. The load bearing surfaces can support multi-position shelves, partitions, fixtures, etc. An opening is provided for walk-in or reach-in access to an interior of the modular space system.