Defiance County

Permit responsibility in unincorporated Defiance County is split across several offices and the County Engineer issues no zoning or building permits. (1) Township zoning permits for residential construction (including ADUs as accessory residential structures, where allowed) are issued by the zoning inspector of the township the parcel sits in - applicants must contact the specific township inspector directly. Not every Defiance County township has adopted zoning; in unzoned townships there is no township zoning permit step, but state building code, floodplain regulation, and septic/well requirements still apply. (2) Residential building permits under the Ohio Residential Code (RCO) for one-, two-, and three-family dwellings in unincorporated Defiance County are administered by the State of Ohio's residential building program through the Defiance County Building Inspection function; commercial construction in unincorporated territory routes to the Ohio Department of Commerce, Division of Industrial Compliance, or to a certified building department under contract. (3) Floodplain development permits in unincorporated areas are administered by the county's designated floodplain administrator under the county's participation in the National Flood Insurance Program. (4) On-site sewage approval is administered by the Defiance County General Health District where no public sewer is available. (5) Driveway access permits onto county roads are issued by the Defiance County Engineer's office (500 Court Street, Suite C, Defiance OH 43512). An ADU project in unincorporated Defiance County therefore typically requires: a township zoning permit (if the township is zoned), a residential building permit, a floodplain development permit if the parcel is in a FEMA SFHA along the Maumee/Auglaize/Tiffin river corridors, on-site sewage approval, and an address assignment.

Process overview: Typical Defiance County unincorporated ADU workflow: (1) Identify the township the parcel sits in (Adams, Defiance, Delaware, Farmer, Hicksville, Highland, Mark, Milford, Noble, Richland, Tiffin, or Washington) and confirm whether that township has adopted zoning. (2) If zoned, contact the township zoning inspector to confirm the parcel's zoning district, whether ADUs or accessory residential structures are permitted, conditional, or prohibited, and to obtain a zoning permit. (3) Apply for a residential building permit under the Ohio Residential Code through the county's building inspection arrangement (state RCO program or contracted certified building department). (4) Submit a floodplain development permit application to the county floodplain administrator if the parcel is in a FEMA Special Flood Hazard Area - the Maumee, Auglaize, and Tiffin river corridors are the primary mapped flood zones. (5) Apply for on-site sewage / septic approval through Defiance County General Health District if the parcel is not on public sewer. (6) Apply for a driveway access permit through the Defiance County Engineer if the parcel takes access from a county road. (7) Receive an address from the county addressing authority. (8) Construct with required inspections; receive Certificate of Occupancy from the building official of record.

Impact fees: Defiance County itself does not levy a county impact fee on residential construction. Fees paid on an unincorporated ADU project are itemized by issuing authority: the township zoning permit fee (set by each township, typically a flat residential fee in the $25-$150 range), the Ohio Residential Code residential permit fee (set by the State of Ohio's program or by the contracted certified building department), the county floodplain development permit fee if applicable, a county health-district septic fee where applicable, and a county engineer driveway access permit fee where applicable. Confirm all current fee schedules with the issuing office at intake.

The Defiance County Auditor is the elected county official responsible for valuing all real property in Defiance County for property-tax purposes, including new ADU improvements added to a host parcel. Defiance County follows the Ohio Department of Taxation's mandated valuation cycle: a sexennial (six-year) full reappraisal in which every parcel is physically reviewed, and a triennial (three-year) update between reappraisals that adjusts values based on local sale data. New ADU square footage and exterior changes are picked up either through the building-permit feed from the building department of record (state RCO program or a contracted certified building department for unincorporated areas, or the relevant municipal building department for parcels inside an incorporated city/village) or through the Auditor's field-canvass during reappraisals. Ohio's owner-occupancy 2.5% reduction (ORC 323.152) and the Homestead Exemption (for qualifying senior, disabled, or surviving-spouse owner-occupants) apply to the principal residence on the parcel but do not exempt the value added by new ADU improvements. An ADU built and rented (not owner-occupied) does not by itself revoke the principal-residence owner-occupancy reduction on the rest of the parcel, but converting the principal residence itself to a rental does. Valuation disputes are heard by the Defiance County Board of Revision under ORC Chapter 5715.

Assessment policy: Sexennial full reappraisal and triennial update cycle, mandated statewide by the Ohio Department of Taxation. New ADU improvement value is added to the parcel's improvement value on the next valuation cycle following construction, picked up via building-permit data from the building department of record and through field canvass. Owner-occupancy 2.5% reduction (ORC 323.152) and Homestead Exemption attach to the principal residence on the parcel and reduce tax owed on that portion but do not exempt the added ADU improvement value. Valuation challenges go to the Defiance County Board of Revision under ORC Chapter 5715.

Defiance County's most operationally significant cross-county overlay is FEMA NFIP floodplain regulation along its three river corridors - the Maumee River (formed at the City of Defiance by the confluence of the Auglaize and Tiffin Rivers), the Auglaize River (entering from the south), and the Tiffin River (entering from the north). These corridors create extensive Special Flood Hazard Areas through both the City of Defiance and unincorporated parcels in Defiance, Delaware, Tiffin, and Noble Townships. The county participates in the National Flood Insurance Program and its floodplain administrator issues development permits for unincorporated SFHA parcels. There is no countywide coastal overlay (Defiance is inland), no wildland-urban-interface fire overlay, and no countywide historic-preservation overlay - the City of Defiance maintains its own designated historic districts but those are municipal, not county. Unzoned townships (where they exist among Defiance County's 12 townships) function as a de facto inverse overlay in that no township zoning permit step is required, though state building code, floodplain, and septic regulation still apply. The Independence Dam State Park area along the Maumee River corridor in Defiance Township involves publicly owned land that constrains private ADU development on those parcels but is not a zoning overlay per se.

• FEMA NFIP Special Flood Hazard Areas along the Maumee, Auglaize, and Tiffin River corridors in Defiance County — Critical facilities must be sited outside the SFHA when feasible. Letter of Map Amendment (LOMA) and Letter of Map Revision (LOMR) processes can adjust effective mapping for parcels with verified higher ground elevations.
• Independence Dam State Park (Maumee River corridor) — Private inholdings and adjacent parcels remain subject to the underlying township zoning (where adopted), Ohio Building Code, county floodplain ordinance, and septic/well requirements.
• Agricultural-use parcels under CAUV (Current Agricultural Use Value) — ADU applicants on CAUV-enrolled parcels should consult the County Auditor before construction to understand recoupment exposure and to verify which portion of the parcel remains in agricultural use after the ADU is added.