ADU Pass
Johnson County
ADU Pass helps homeowners in Johnson County, Kansas navigate the permit paperwork for building an accessory dwelling unit. We cover 10 cities and 35 ZIP codes in this county.
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County ADU details
County ADU ordinance
Johnson County, KS (620,000 residents in suburban Kansas City) administers a county zoning ordinance for unincorporated territory. Major incorporated cities include Overland Park, Olathe, Lenexa, Shawnee, Leawood, Mission, Prairie Village, Gardner, Spring Hill, De Soto. Each sets its own ADU rules.
Code citations:
State-floor overlay: Kansas has not enacted statewide ADU preemption.
Adopting body: Johnson County Board of Commissioners; city councils
County permitting (unincorporated parcels)
Johnson County issues building permits for parcels in unincorporated territory through its development services / planning department, with separate review tracks for zoning conformance, building-code compliance, on-site sewage where applicable, floodplain compliance, and addressing. Inside incorporated municipalities, city departments handle their own permits; the county's authority is geographically limited to unincorporated territory. An ADU permit application is typically processed as a residential building permit with a zoning verification step against the county's ordinance for the parcel's zoning district.
Process overview: Typical workflow: (1) jurisdictional verification (parcel confirmed in unincorporated Johnson County, not inside city limits or extra-territorial jurisdiction); (2) zoning verification against the county ordinance; (3) building-code plan review against the adopted state building code; (4) site-plan, septic (where applicable), and floodplain review; (5) issuance, construction with inspections, and certificate of occupancy.
Impact fees: Johnson County permit fees are itemized at intake. Counties in Kansas commonly do not levy municipal-style impact fees on residential additions in unincorporated areas; verify current fee schedule at the development-services counter.
County assessor
The Johnson County property assessor / equalization office maintains parcel-level assessment records for all real property in Johnson County. ADU additions are typically captured as improvements to the host parcel via shared permit data with the building department. Kansas property-assessment rules govern annual revaluation cycles, homestead or principal-residence caps where applicable, and the procedures for protesting an appraisal.
Assessment policy: Improvement value for an ADU is added to the parcel record on the next regular revaluation cycle. Homestead / principal-residence caps where applicable shield the existing structure from rapid valuation increases but do not exempt new improvement value.
County overlays (2)
Johnson County administers flood-hazard, and (where mapped) coastal, wildland-fire, historic, and airport overlays that shape ADU project feasibility. The most consistent overlay across the county is FEMA NFIP floodplain regulation; other overlays apply to specific geographies inside the county.
- FEMA NFIP Special Flood Hazard Areas in Johnson County — A new ADU in a mapped SFHA must be elevated to or above the Base Flood Elevation; cost impact on the project is often material.
- Historic districts and individually-listed historic resources
Kansas state — ADU law and programs
State ADU law
Kansas enacted statewide ADU-permissive housing legislation in the 2026 session. Senate Bill 418, the By-Right Housing Development Act, was signed by Governor Laura Kelly on 2026-04-08. The bill requires every Kansas city and county to ministerially approve housing developments — including single-family homes, townhouses, and accessory dwelling units — that meet existing local zoning code criteria, without discretionary review. Rezoning to single-family residential cannot be subject to double super-majority protest-petition review. Third-party private inspectors are permitted when the local government does not perform required inspections within 15 days of request. The bill follows the Pacific Legal Foundation model 'By-Right Housing Development Act' and 'Fair Zoning Act'. SB 418 does not preempt local zoning standards (size, setback, parking, etc.), but it forces ministerial approval where standards are met.
State financing programs
Kansas does not operate an ADU-specific statewide loan, grant, or forgivable-loan program. The Kansas Housing Resources Corporation (KHRC) administers general first-time-homebuyer, down-payment-assistance, weatherization, and rural-home-loan-guarantee programs. The First Time Homebuyer program offers a 0% interest second mortgage of 15% or 20% of purchase price, forgiven after 10 years of occupancy. None target ADU construction directly; an ADU may be financed through standard rehab or construction-loan products if part of a qualifying primary-residence purchase or refinance.
State housing programs
Kansas's primary state-level ADU program is the SB 418 (2026) By-Right Housing Development Act, which mandates ministerial approval of conforming ADU applications and permits third-party inspection when local agencies miss the 15-day inspection window. There is no statewide pre-approved ADU plan catalog, no statewide ADU rebate program, and no statewide ADU impact-fee waiver. The SB 418 ministerial-approval requirement is the dominant state-level intervention.
- SB 418 By-Right Housing Development Act — Cities and counties must approve single-family homes, townhouses, and ADUs that meet existing zoning standards ministerially, without discretionary review. Bars double super-majority protest-petition review for rezoning to single-family residential.
- SB 418 Third-Party Inspection Provision — When a local government fails to perform a required residential inspection within 15 days of request, the developer/owner may engage a qualified third-party inspector. Removes city/county inspection-backlog as a permit bottleneck for ADUs.
Federal (United States) — ADU-relevant rules and programs
Federal ADU law
The United States has no federal statute that directly regulates accessory dwelling unit entitlement or design. Land-use authority over ADUs resides with states and local governments under the traditional police power. Federal engagement is limited to financing (Fannie/Freddie/FHA/VA/USDA), flood insurance (FEMA/NFIP), and discretionary housing programs (HUD), which are recorded in sibling sections of this file.
Federal financing programs
Federal housing-finance agencies and GSEs set nationwide underwriting rules that govern whether an ADU can be financed, appraised, and counted toward mortgage qualifying income. The relevant actors are Fannie Mae, Freddie Mac, FHA (HUD), VA, and USDA Rural Development.
Federal tax credits
There is no ADU-specific federal tax credit. ADUs may incidentally qualify for existing federal energy-efficiency and clean-energy tax credits when the ADU construction includes qualifying measures.
Federal housing programs
HUD administers several discretionary programs that can fund ADU-related activity at the grantee's election, but none is an ADU-specific program.