ADU Pass
Clinton County
ADU Pass helps homeowners in Clinton County, Ohio navigate the permit paperwork for building an accessory dwelling unit. We cover 7 cities and 9 ZIP codes in this county.
Map
County ADU details
County ADU ordinance
Clinton County, Ohio (rural south-central Ohio county between Dayton and Cincinnati, ~42,500 residents, county seat Wilmington, 13 townships, six incorporated places including Wilmington (city), Blanchester (village, shared with Warren and Brown counties), Clarksville (village), Martinsville (village), Midland (village), New Vienna (village), Port William (village), and Sabina (village)) is one of the relatively small number of Ohio counties that has adopted county-tier rural zoning under O.R.C. Chapter 303. The current operative document is the Clinton County Zoning Resolution, originally adopted in the late 20th century with the most recent comprehensive update effective 2025. Unlike Adams County, Athens County, and most rural Ohio counties, Clinton County exercises affirmative county-tier zoning authority over 11 of its 13 townships. The two outliers are Clark Township and Washington Township, which have not opted into the county zoning resolution and are therefore unzoned for land-use purposes (the Ohio Residential Code and Clinton County Health Department septic rules still apply there). For ADU purposes the county zoning resolution does not use the term 'accessory dwelling unit' or 'ADU' but does regulate dwellings as a permitted use in residential and agricultural districts; second dwellings on a single parcel are generally not a permitted accessory use and typically require a Conditional Use approval or a lot split. Permitting in unincorporated zoned townships requires a Clinton County Zoning Permit issued by the County Building and Zoning Department before a building permit can be issued.
County assessor
Assessment policy: The Clinton County Auditor (Terence G. Habermehl as of 2026) is the elected property-assessment authority under O.R.C. § 5713.01. Ohio assesses real property at 35% of true value (O.R.C. § 5713.03). New ADU construction is added to the parcel record on the next regular revaluation cycle and reassessed at true value as of January 1 following completion. The Owner Occupancy Credit (O.R.C. § 323.151 et seq.) gives a 2.5% reduction in tax on owner-occupied homestead; the Homestead Exemption (O.R.C. § 323.152) reduces taxable value by $25,000 for owners 65+ or totally and permanently disabled, subject to income tests. Clinton County also administers Current Agricultural Use Valuation (CAUV) under O.R.C. § 5713.30 - § 5713.38, which is material here because much of the county outside Wilmington is enrolled farmland; the Clinton County Auditor charges a one-time $25 application fee for CAUV, mailed renewals are filed each year before the first Monday in March, and a three-year recoupment applies to land removed from CAUV. An ADU built on a CAUV parcel can trigger a partial recoupment if the dwelling reduces qualifying agricultural acreage below program thresholds; applicants should consult the Auditor before construction on CAUV land. Under O.R.C. § 5713.17, the owner must notify the Auditor of any construction or improvement valued over $2,000.
County overlays (5)
Known county issues (5)
- other — ADU economics differ sharply by township. In the 11 zoned townships, ADU feasibility is gated by Board of Zoning Appeals discretion or by surveyor and recording costs for a lot split; in Clark or Washington townships there is no county zoning prohibition on a second dwelling, and the only land-use review is the Health Department septic capacity check.
- other — ADU applicants benefit from a contracted review with measurable turnaround and a stable schedule, but should expect plan-review questions to come from Warren County staff routed through Clinton County, not directly. Coordination friction is minimal in practice but worth flagging.
- other — Researchers and homeowners proposing an ADU within roughly 5 miles of Wilmington Air Park should check the FAA Part 77 surface and any voluntary airport-disclosure overlay before finalizing height and siting decisions.
- policy-review — Researchers should monitor the Ohio General Assembly for any future ADU preemption proposal; until one passes, Clinton County's ADU permissibility remains a function of township-specific zoning posture and Board of Zoning Appeals discretion.
- other — Rural Clinton County ADU economics commonly include a CAUV-recoupment line item that researchers should add to project cost. Applicants should consult the Auditor's CAUV staff before construction on CAUV-enrolled land to estimate the recoupment.
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.