Except in a planned unit development or as authorized in subsection (b) of this section:no more than 1 principal detached structure may be located on:any residential lot; or any lot adjacent to a residential lot; and no principal detached structure or any other free-standing structure may be located with any other principal structure on the same:residential lot, except as specified in <cite data-path="32|§1-210">§ 1-210</cite> {“Use and site development standards”} or <cite data-path="32-§15-601">§ 15-601</cite> {“Permitted projections and obstructions into required yards”}; or any lot adjacent to a residential lot. Notwithstanding subsection (a) of this section, the Zoning Administrator shall approve the construction of more than 1 principal detached structure or other free-standing structure on a residential lot or any lot adjacent to a residential lot, if:the development otherwise would conform to the requirements of this Article; and the requirements of site plan review and design review are met.