Building permits, zoning and septic rules in Union County, Ohio

Yes. Building permits are required for construction in areas served by the Union County Building Department, and plumbing, electrical and mechanical work also requires permits¹. The county does not provide building-code enforcement in Unionville Center, incorporated Plain City or the City of Dublin; Dublin has its own building department, while the West Jefferson Building Department handles incorporated Plain City². Small residential sheds of 200 square feet or less and commercial sheds of 120 square feet or less are exempt, and patios do not require a building permit, although zoning approval may still apply¹. An owner-builder does not receive a general exemption from plan approval: the owner must submit plans to the building department with jurisdiction and wait for approval before starting⁶. An agricultural building qualifies for the building-code exemption only after the township zoning inspector determines that its use is agricultural rather than residential accessory or commercial storage; a later residential or commercial conversion requires change-of-occupancy approval and compliance with the new use's code requirements².

The Union County Building Department reviews construction documents and issues permits in its service area from 233 West 6th Street in Marysville⁷. Applicants submit the online application with drawings and specifications, then secure plan approval, local zoning approval, any required Health Department approval and payment of fees². Applications with construction drawings must be reviewed within 30 days, while permits without drawings are typically issued within 1 week². The residential fee schedule charges a $35 application fee and a $105 plan-review fee for a new building, addition or accessory building, both due when the application is submitted, with the permit fee based on square footage plus a 1% Ohio surcharge⁸. Inspections are mandatory for work constructing, altering or adding to one-, two- and three-family residences⁹. A regulated building cannot be used or occupied until required inspections are complete and the building official issues a Certificate of Occupancy¹⁰.

Union County does not administer a countywide zoning ordinance: zoning authority has been voted to the individual townships, with municipal zoning inside cities and villages³. Zoning permits are required in most municipalities and all townships except Jackson Township¹. Minimum road frontage, setbacks and minimum square feet per household vary with the local district¹. A parcel's mailing address alone therefore does not answer what can be built: identify the governing township or municipality and ask its zoning official whether the intended use is allowed before commissioning plans. Jackson Township's zoning-permit exception does not erase applicable building, septic, well, driveway or floodplain requirements^1,4. Union County's building workflow treats local zoning approval as a separate prerequisite where required².

Where public sewage service is unavailable, Union County allows an on-site household sewage treatment system, but the site must also reserve space for a backup system⁴. Before installation, submit the site and design application, house plan, soil report from a registered soil scientist, and applications for both installation and operating permits to the Union County Health Department⁴. The installer must arrange an inspection before backfilling, and the Health Department returns 12 months after a new system is completed; later operation-and-maintenance inspections depend on system type⁴. Only about 0.1% of Union County soils are rated without severe limits for a conventional drain field, so settle septic feasibility before choosing a house location¹¹. Site-specific soil, water table, bedrock, slope and floodplain conditions can constrain the approved design⁴.

We could not confirm a countywide rule allowing an RV or tiny home as a residence on private land. The applicable township or municipality controls zoning, including district-specific setbacks and minimum square feet per household, so ask that zoning official about the proposed unit and occupancy before buying¹. A tiny home used as a dwelling still faces the applicable building-permit process in the Union County Building Department's service area¹. An off-grid plan also needs an approved septic system where public sewage service is unavailable, and a private well requires a Health Department permit and a site inspection before permit issuance^1,4. A manufactured home generally cannot be occupied until the state inspector issues its inspection seal, apart from the temporary-occupancy exception¹².

1. Identify the township or municipality and confirm permitted use, minimum dwelling size, frontage and setbacks with its zoning official¹.
2. Confirm whether the Union County Building Department or an alternative authority serves the parcel².
3. If public sewer is unavailable, obtain a soil report and complete the Health Department's septic site-and-design process⁴.
4. Apply to the Health Department for a private-well permit and complete the required site inspection before permit issuance¹.
5. Obtain a driveway permit from the Union County Engineer for a county or township road, or contact the Ohio Department of Transportation for a state highway¹.
6. If the home site is in a flood hazard area, obtain the county permit for unincorporated land; check with local officials inside a municipality¹.
7. Submit the building application and drawings, secure approvals, pay the fees, and wait for issuance before work begins^1,2.
8. Complete required inspections and obtain the Certificate of Occupancy before using the building^9,10.

Confirm septic capacity, water, legal access, floodplain status and any planned land split before closing. Only about 0.1% of Union County soils are rated without severe limits for a conventional drain field, and the Health Department requires a soil report for the septic application^4,11. A private well needs a permit and a site inspection before permit issuance¹. The County Engineer permits new driveways on county and township roads; the Ohio Department of Transportation handles state-highway access¹. A home planned within a flood hazard area in unincorporated Union County needs a flood hazard area permit; inside a municipality, ask city or village officials¹. In unincorporated Union County, selling or subdividing part of a property must follow the Union County Subdivision Regulations, and the County Engineer reviews the plats^13,14. Verify the local zoning district because setbacks, frontage and dwelling size vary¹.