Blue Springs, MO Accessory Structures: ADU Rules (2026)

Blue Springs' Unified Development Code treats the accessory dwelling unit as its own building type under Section 405.020, and it is available only when paired with a detached house on the lot; a stand-alone ADU without a principal detached house is not a permitted arrangement. When the unit sits in a detached accessory structure, it must also satisfy the accessory-use standards cross-referenced at Section 405.060(A)(1). Placement is tightly controlled: the front setback requires the ADU to sit at least 5 feet behind the rear building line of the primary house, unless it is attached to a detached garage, in which case the minimum drops to 10 feet behind the primary house's front building line.

Side and rear setbacks are 5 feet minimum, except on estate lots, where the ADU instead follows the same setback standards that apply to the primary building itself. Height is capped at 18 feet or 1.5 stories, and the code specifies the ADU can never be taller than the primary house regardless of that cap. Detached ADUs must keep at least 5 feet of separation from any other building on the lot. Size is doubly capped: the footprint cannot exceed 50% of the primary house's footprint, to an absolute maximum of 700 square feet, and that footprint counts toward the lot's overall building coverage limit; the total living area cannot exceed 50% of the primary house's square footage, up to a hard ceiling of 1,200 square feet. Community Development staff review these standards during building permit review for any new ADU in the city.