Mark Center

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.

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.