ADU Design in Defiance, OH

ADU Design in Ohio: what governs your project

Ohio has no statewide ADU statute; ADUs are regulated entirely by local zoning. Columbus, Cleveland, and Cincinnati each maintain their own accessory-dwelling standards within their zoning codes.

Energy code

Permitting varies by jurisdiction: many Ohio cities cap ADU floor area as a percentage of the primary home, require owner occupancy of one unit, and use standard residential permits. Older neighborhoods may need zoning variances for lot coverage.

Permitting & plan check

Ohio uses a certified building department system: the Ohio Board of Building Standards certifies local departments to perform non-residential plan review and inspection. Where no certified local department exists, the state Division of Industrial Compliance handles review. Building permits are issued locally under the Ohio Building Code.

Good to know

• Northeast Ohio's snow belt, downwind of Lake Erie, produces some of the highest snow loads in the state due to lake-effect snow.
• Western Ohio has experienced notable historic earthquakes near Anna, and the state carries low-to-moderate seismic design requirements.
• Ohio's building code is administered by the Ohio Board of Building Standards, with plan review performed by state-certified local building departments.

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