ADU Permit Requirements in Clermont County, OH
Clermont County Permit Central issues building, electrical, mechanical, and plumbing permits for unincorporated Clermont County in the east Cincinnati metro (includes Miami Twp, Union Twp, Batavia Twp, Goshen Twp, and adjacent areas). Codes in force: 2019 Residential Code of Ohio (RCO) with April 2024 amendments, based on the 2018 IRC. NEC 2017. IECC Climate Zone 4A: R-49 attic, R-20 walls typical. Ground snow load 20 psf, frost depth 30 inches (RCO R403.1.4). Ice-barrier underlayment required per RCO R905.1.2. Plumbing, electrical, HVAC, and hydronics contractors licensed by the Ohio Construction Industry Licensing Board (OCILB) under ORC 4740, with an owner-builder carveout for primary residence. Septic permits issued by Clermont County Public Health at (513) 732-7499. County-road right-of-way work through Clermont County Engineer. ODOT approval required for driveway work on SR 32, SR 125, SR 28, US 50, or US 52. Duke Energy handles electrical interconnect. Passive radon mitigation per RCO Appendix F in new basements. Pool barriers per RCO Appendix AG. Published fee schedule in PDF.
By Joey, Founder · Last verified April 22, 2026 · How we research →
When you need a ADU permit in Clermont County
A detached accessory dwelling unit (ADU) requires building, plumbing, electrical, and mechanical permits. Confirm ADUs are allowed in the township's zoning resolution before applying. Septic capacity must be reviewed by Clermont County Public Health at (513) 732-7499 if the property is on septic.
An attached ADU (in-law suite, garage conversion with kitchen) requires building, plumbing, and electrical permits. Septic capacity must be reviewed by Clermont County Public Health at (513) 732-7499 if on septic.
ADU Permit Costs: Clermont County vs. Nearby
| City | Estimated Fee |
|---|---|
| Clermont County | N/A |
| Franklin County | $500 – $5,000 |
| Columbus | $500 – $5,000 |
| Cleveland | $500 – $5,000 |
Fees shown are estimates based on local building code data. Actual fees may vary based on project scope and valuation. See all Clermont County permit costs →
Zoning & HOA Considerations
ADU regulations vary dramatically by state and city. Many states (CA, OR, WA) have preemption laws that override local zoning restrictions. Check both state law and local zoning before designing.
If you live in an HOA community: hOAs have traditionally restricted ADUs, but state preemption laws in CA, OR, WA, and other states now limit HOA authority over ADUs. Check your state's ADU laws, your HOA may not be able to block construction even if CC&Rs appear to prohibit it.
Estimated Project Timeline in Clermont County
Here's a typical timeline for a adu project in Clermont County, OH:
Timeline is based on Clermont County's typical about 4 weeks permit processing time. Actual timelines vary by project complexity, completeness of application, and current department workload.
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Frequently Asked Questions
Contact Clermont County's building department for current ADU permit fee information. Fees typically vary based on project scope and valuation.
It depends on the specifics of your project. Some smaller ADU projects may be exempt from permit requirements, while larger ones typically require a permit. Use our free lookup tool to check your specific situation.
Working without a required permit in Clermont County can result in fines, stop-work orders, being required to remove completed work, and complications when selling your home. It's always best to check first.
Typical approval time for ADU permits in Clermont County is about 4 weeks. More complex projects may take longer if plan review is required.
If you live in an HOA community, you may need architectural review approval in addition to a building permit. HOA rules and city building codes are separate, you may need to satisfy both. Review your CC&Rs and submit to your HOA's architectural review committee before starting work.
Learn More About ADU Permits
Read our complete guide covering permit requirements, costs, common exemptions, and the application process.
Read ADU Guide →