ADU Pass
Clark County
ADU Pass helps homeowners in Clark County, Ohio navigate the permit paperwork for building an accessory dwelling unit. We cover 11 cities and 17 ZIP codes in this county.
Map
County ADU details
County ADU ordinance
Clark County, Ohio (~133,500 residents; county seat Springfield; 10 townships - Bethel, German, Green, Harmony, Mad River, Madison, Moorefield, Pike, Pleasant, and Springfield Township; incorporated places Springfield (city, county seat, ~59,680), New Carlisle (city, ~5,693), Catawba (village), Donnelsville (village), Enon (village - partly extends into Greene County), Medway (village), North Hampton (village), South Charleston (village), South Vienna (village), and Tremont City (village)) DOES exercise county-tier zoning under O.R.C. Chapter 303. Clark County is among the minority of Ohio counties that have adopted a county Rural Zoning Resolution (Resolution adopted under O.R.C. 303.02 et seq. by the Board of County Commissioners); the county Combined Planning & Zoning office administers it for unincorporated parcels in any township that has not adopted its own independent township zoning resolution under O.R.C. Chapter 519. Most Clark County townships (including Mad River, Bethel, Springfield Township, and German) operate under the county Rural Zoning Resolution rather than maintaining a separate township ordinance; a few have their own (Green Township, Moorefield Township, and Pleasant Township each carry stand-alone zoning resolutions). The county Rural Zoning Resolution treats accessory dwelling units as 'accessory residential structures' or 'second dwellings on a parcel,' with permission turning on the parcel's zoning district (A-1 Agricultural and R-1/R-2/R-3 Residential have differing accessory-use allowances), minimum lot area, setbacks, and a septic-capacity finding from the Clark County Combined Health District. Ohio is a home-rule state under Article XVIII of the Ohio Constitution, which insulates municipalities from county zoning inside their corporate limits; the county ordinance therefore does NOT govern parcels inside Springfield, New Carlisle, or any of the incorporated villages - each of those administers its own zoning code. The Mad River corridor through Mad River and Bethel townships is a meaningful overlay-adjacent factor because Mad River is a state-designated scenic river and a heavily-mapped FEMA Zone AE floodplain.
State-floor overlay: No Ohio statewide ADU preemption is in force as of 2026-05-20. Clark County and each of its incorporated municipalities and zoned townships retain full authority over ADU zoning and permitting under O.R.C. Chapters 303, 519, and 713 plus Ohio Constitution Article XVIII.
Adopting body: Clark County Board of Commissioners (county Rural Zoning Resolution); individual township trustees for the townships with stand-alone resolutions (Green, Moorefield, Pleasant); city councils and village councils for the incorporated places.
County assessor
Assessment policy: The Clark County Auditor (John Federer, 2026; address 31 N. Limestone Street, Springfield) 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). The most recent Clark County sexennial reappraisal was 2023, with a triennial update due 2026; new ADU construction is added to the parcel record on the next triennial / sexennial cycle and reassessed at true value as of January 1 following completion. The Ohio Owner Occupancy Credit (O.R.C. § 323.151 et seq.) provides 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. Clark County administers Current Agricultural Use Valuation (CAUV) under O.R.C. § 5713.30 - § 5713.38; CAUV coverage is significant in the eastern and southern townships (Pike, Harmony, Madison) where Madison Plains agricultural land dominates. An ADU built on a CAUV-enrolled parcel may trigger a three-year CAUV recoupment if the dwelling reduces qualifying agricultural acreage below the 10-acre CAUV threshold. Under O.R.C. § 5713.17, the owner must notify the Auditor of any construction or improvement valued over $2,000. Clark County also runs a Board of Revision for valuation challenges (filing window typically January 1 - March 31 for prior-year valuation).
County overlays (5)
Known county issues (7)
- other — ADU posture in unincorporated Clark County is meaningfully more structured than in most rural Ohio counties: there IS a county zoning ordinance to comply with on most parcels, but Clark County is also a certified residential building department with relatively quick permit cycles - the trade is more rules in exchange for shorter wall-clock.
- other — Enumeration of Clark County cities here includes 'yellow-springs' for fidelity to the city-highlights tree, but consumers should not attribute Yellow Springs's ~3,793 residents to Clark County's housing stock or rent base. Clark County's actual incorporated places are Springfield (city, county seat), New Carlisle (city), Catawba (village), Donnelsville (village), Enon (village - partly in Greene County), Medway (village), North Hampton (village), South Charleston (village), South Vienna (village), and Tremont City (village).
- other — An ADU application in Enon may route through Greene County administrative systems (assessor, health district, county engineer) even though the village itself sits in Clark County's enumeration. Coverage statistics in the Clark County rollup attribute Enon entirely to Clark for housing-stock counting, which slightly overstates Clark's actual portion.
- other — ADU construction on a Mad-River-corridor parcel adds 15-30 days for ODNR consultation and may require professional engineering for stormwater / thermal-discharge / riparian-buffer design. Cost impact for a typical streamside ADU is 5-12% over an interior-parcel equivalent.
- other — Most Clark County parcels are well outside the affected zone, but parcels in southern Springfield Township within ~3 miles of the airport should consult Clark County Combined Planning & Zoning early in the design process.
- policy-review — Researchers should monitor the Ohio General Assembly for any future ADU preemption proposal; until one passes, ADU permissibility in Clark County depends on the parcel's specific zoning jurisdiction (county Rural Zoning Resolution, one of three township resolutions, or one of the ten municipal codes).
- other — Wall-clock for the first Springfield ADU applications under the new code has occasionally exceeded the formal 35-day cycle by 7-14 days as Planning works out interpretive precedent. By late-2026 this should normalize.
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.