Guernsey County

Guernsey County does not operate a State-of-Ohio-Board-of-Building-Standards (BBS) certified residential building department. Residential ADU work on parcels in unincorporated Guernsey County (whether in a zoned or unzoned township) proceeds without a county building permit; the Ohio Residential Code remains the technical standard but is not actively enforced parcel-by-parcel. Permitting in the unincorporated balance is a combination of township-zoning compliance (where applicable), health-department on-site sewage and private water permits, county floodplain review (within FEMA SFHAs), county engineer right-of-way permits, and 911 addressing. Commercial and multi-family work falls to the Ohio Department of Commerce, Division of Industrial Compliance. Inside the city of Cambridge and the ten villages, the municipality handles its own permits.

Process overview: Typical workflow for an unincorporated Guernsey County parcel: (1) confirm the parcel is outside any incorporated municipality (Cambridge, Byesville, Lore City, Kimbolton, Pleasant City, Senecaville, Cumberland, Old Washington, Quaker City, Buffalo, Derwent); (2) determine the parcel's township and check whether that township has a Chapter 519 zoning resolution — if yes, obtain a zoning compliance certificate from the township zoning inspector before construction; (3) Cambridge-Guernsey-Noble County Health Department review for septic (Household Sewage Treatment System) and private water supply where municipal utilities are unavailable; (4) Guernsey County floodplain coordinator review if the parcel is in a FEMA Special Flood Hazard Area (Wills Creek, Salt Fork, Leatherwood Creek, Buffalo Creek corridors); (5) Guernsey County Engineer driveway / right-of-way permit if a new access cut to a county road is needed; (6) 911 address assignment via Guernsey County 9-1-1; (7) construction (residential RCO compliance is the owner's legal responsibility but is not actively inspected by a county building department); (8) county auditor parcel update at the next sexennial reappraisal or triennial update.

Impact fees: Guernsey County does not levy municipal-style impact fees on residential additions in unincorporated areas. Fees are limited to per-permit fees at the health department (HSTS permit fee schedule changes annually — confirm at intake), the engineer's office, and (where applicable) the township. The city of Cambridge and the villages each set their own permit fee schedules.

Real property valuation in Guernsey County is performed by the elected Guernsey County Auditor (Ohio uses the title 'County Auditor' rather than 'Assessor'). Ohio counties operate a six-year reappraisal cycle with a three-year update in between (O.R.C. Sec. 5713.01 and Sec. 5715.24). An ADU added to a Guernsey County parcel is captured as an improvement to the host parcel at the next sexennial reappraisal or triennial update, and may also be picked up earlier if a building permit is reported or the improvement is visible to the auditor's field staff. Ohio assesses real property at 35 percent of true (market) value (O.R.C. Sec. 5715.01). Owner-occupied residential parcels qualify for the 2.5 percent owner-occupancy tax credit (O.R.C. Sec. 323.152(B)); whether that credit extends to an ADU on the same parcel depends on whether the Auditor classifies the ADU as part of the principal residence (one credit) or as a separately-occupied unit.

Assessment policy: Ohio assesses real property at 35 percent of true (market) value (O.R.C. Sec. 5715.01). Counties reappraise every six years with a triennial update (O.R.C. Sec. 5713.01, Sec. 5715.24). The Homestead Exemption (O.R.C. Sec. 323.152(A)) is available to owner-occupants who are 65+ or permanently and totally disabled, subject to a means test for new applicants. The 2.5 percent owner-occupancy credit (O.R.C. Sec. 323.152(B)) reduces the residential millage on the owner's principal residence. ADU treatment under the owner-occupancy credit depends on whether the Auditor classifies the ADU as part of the principal residence (one credit) or as a separate residential unit (potentially excluded from the credit on the portion attributed to the ADU). Guernsey County's most recent sexennial reappraisal cycle and triennial update timing should be confirmed with the Auditor at intake.

Guernsey County's principal county-administered overlay affecting ADU feasibility is (a) FEMA NFIP Special Flood Hazard Areas along Wills Creek (the major drainage through Cambridge and Byesville), Salt Fork (the dammed reservoir of Salt Fork State Park east of Cambridge), Leatherwood Creek, and Buffalo Creek, administered by the Guernsey County Floodplain Coordinator under the county's NFIP-participating floodplain ordinance. Beyond flood, the dominant Guernsey-specific factors are (b) extensive Utica/Marcellus shale oil-and-gas activity, with widespread leases, unitization orders, and surface-use easements that can constrain ADU siting on private parcels under O.R.C. Chapter 1509, and (c) the legacy of historic coal mining (Cambridge Limestone and various coal seams) and clay extraction, which expresses as undermined ground and as Abandoned Mine Land (AML) features in parts of the county. The county itself does not maintain a historic-district overlay; portions of Cambridge's downtown carry a National Register district administered through Cambridge's own historic preservation framework. Wildland-urban-interface fire mapping is not maintained as a binding overlay in Ohio at the county level.

• Guernsey County Floodplain Management (FEMA NFIP participation) — A new ADU in a Zone AE SFHA parcel must be elevated to or above the Base Flood Elevation per the local floodplain ordinance and 44 CFR 60.3. Substantial-improvement triggers apply when an ADU project's cost exceeds 50 percent of the host structure's pre-improvement market value. The 1998 Wills Creek flood and subsequent events make this a live concern in central Guernsey County.
• Utica / Marcellus shale unitization and surface-use easements — This is a parcel-level title and surface-easement issue rather than a zoning overlay; the county itself does not administer oil-and-gas operations (ODNR has sole-and-exclusive jurisdiction under O.R.C. Sec. 1509.02). It is included here because it is one of the most common Guernsey-specific factors that derails an otherwise-allowed ADU.
• Historic coal mining and Abandoned Mine Land (AML) features — Subsidence is not a zoning overlay in the regulatory sense — the county does not block construction — but it is a material constructability and insurance consideration distinguishing ADU work in Guernsey County from ADU work in non-mining Ohio counties.