Byesville

Guernsey County is in east-central Ohio along the I-70/I-77 interchange corridor, with the county seat at Cambridge. Like the rest of Ohio, the county operates under home-rule (Ohio Const. Art. XVIII, Sec. 3), with land-use authority split between (a) the county under O.R.C. Chapter 303 (permissive county rural zoning), (b) the 19 civil townships of Guernsey County under O.R.C. Chapter 519 (permissive township zoning), and (c) the incorporated municipalities under their home-rule zoning power. Guernsey County has not adopted countywide rural zoning under Chapter 303; there is no county-administered ADU ordinance. Operative ADU rules in unincorporated parcels come from the township zoning resolution (where the township has adopted one) or, where the township is unzoned, from no zoning at all. Inside incorporated municipalities (Cambridge, Byesville, Lore City, Kimbolton, Pleasant City, Senecaville, Cumberland, Old Washington, Quaker City, Buffalo, Derwent), each municipality sets its own ADU rules.

• Ohio Const. Art. XVIII, Sec. 3 (Home Rule)
• O.R.C. Chapter 303 — County Rural Zoning
• O.R.C. Chapter 519 — Township Zoning

State-floor overlay: No Ohio statewide ADU preemption is in force as of 2026-05-20. The Ohio Residential Code (OBBS-adopted IRC with Ohio amendments) sets the building-code floor for one- and two-family dwellings, but use, density, setbacks, parking, and owner-occupancy are local. The county itself retains no zoning authority because Guernsey County has not adopted Chapter 303 rural zoning.

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.

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.