ADU rules in Johnson County, KS — also called accessory dwelling unit regulations or granny flat ordinances — cover setbacks, owner-occupancy, parking, and permit requirements.
Kansas has no statewide ADU mandate; ADU regulation is delegated to counties under K.S.A. 19-2901 et seq. Johnson County's Zoning Regulations permit internal, attached, and detached accessory dwelling units (ADUs) by right in rural and residential districts under Article 18, Section 7(D), subject to use-specific performance standards. ADUs are accessory and secondary to a principal dwelling unit and must remain under the same ownership in all respects. Most reviews are administrative; some site conditions trigger a public hearing before the Board of County Commissioners.
Authority: K.S.A. 19-2901 et seq. (county zoning) and the Johnson County Zoning Regulations administered by the Johnson County Planning Department (111 S. Cherry St., Olathe). Article 18, Section 7(D) sets use-specific performance standards for accessory dwelling units. Three ADU types are recognized — internal (within the principal dwelling), attached (sharing a wall), and detached (a separate accessory building). The ADU must be accessory and secondary to the principal dwelling unit, both must be on the same parcel under common ownership, and the principal dwelling must be the larger of the two. The application sequence is: (1) verify the address is in unincorporated Johnson County, (2) complete the ADU Worksheet, (3) submit a development plan, legal description, and narrative for administrative review, (4) obtain an ADU Certificate, (5) apply for a building permit, and (6) receive a Zoning Permit after final inspection. Johnson County's incorporated cities — Overland Park, Olathe, Lenexa, Shawnee, Mission, Leawood, Prairie Village, Merriam, Roeland Park, De Soto, Edgerton, Fairway, Gardner, Mission Hills, Mission Woods, Spring Hill, Westwood, and Westwood Hills — administer their own ADU rules and are not governed by the County's ADU regulations.
Building or occupying an unpermitted ADU is a zoning violation. The Planning Department's Code Enforcement office (913-715-2205) investigates on a complaint basis and may issue notices of violation, stop-work orders, and refer unresolved cases to the Johnson County Counselor for civil injunctive relief. Each day a violation continues may be treated as a separate offense. Unpermitted electrical, plumbing, or structural work may also trigger separate building-code enforcement and refusal of a Certificate of Occupancy.
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