Does Montgomery County, OH have its own adu rules ordinance?

No. Montgomery County, OH does not appear to have a local adu rules ordinance, Ohio state law applies instead. The rules summarized on this page come from Ohio R.C. Chapter 519 - Township Zoning.

Key Facts Ordinance Text Full Breakdown Violations FAQ Sources More in Montgomery County

Montgomery County, OH Accessory Structures: ADU Rules (2026)

Some Restrictions

Compiled from the official code textEditor Martyn O'NeillLast verified September 2026

ADU rules in Montgomery County, OH, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.

Key Facts

Zoning authority: Your city, village, or township
County ADU ordinance: None (home rule)
Township enabling law: ORC Chapter 519
Building standard: Ohio Residential Code
County seat: Dayton, Ohio

ADU Eligibility Quick-Check

An Accessory Dwelling Unit (ADU) is a smaller, independent living unit on the same lot as a single-family home: converted garages, detached cottages, basement or attic conversions, and attached additions all qualify. Most states have streamlined ADU permitting since 2020, but local rules still control size, height, and setback.

Is your lot zoned single-family or multi-family residential?
Does your lot have at least 1,200 sq ft of buildable space?
Is your existing home owner-occupied (in most states this is not required, but some require it for ADU permits)?
Will the ADU stay under your state's size cap (commonly 850-1,200 sq ft for detached)?
Can you provide one off-street parking space (waived in many states within 0.5 mi of transit)?

If you answered 'yes' to most of these, you likely qualify in Ohio under recent ADU streamlining laws. The Montgomery County, OH rules below cover local size, height, and setback requirements.

Summary

Montgomery County has no countywide accessory-dwelling-unit ordinance. Whether an ADU, in-law suite, or backyard cottage is allowed on your lot is decided by your city, village, or township zoning code, not by county government.

City-specific rules exist: Dayton has its own adu rules rules that differ from Montgomery County's county-level regulations. If you live in Dayton, check the city-specific page instead.

The board of township trustees may regulate by resolution, in accordance with a comprehensive plan, the location, height, bulk, number of stories, and size of buildings and other structures... and the uses of land for trade, industry, residence, recreation, or other purposes in the unincorporated territory of the township.

Source: Ohio R.C. Chapter 519 - Township ZoningView official code

Full Breakdown

Ohio is a home-rule state for land use. Cities and villages zone within their limits, and townships zone unincorporated land under Ohio Revised Code Chapter 519. Montgomery County is heavily incorporated (Dayton plus roughly 25 municipalities and townships such as Washington, Miami, Harrison, and Jefferson), so there is no single countywide ADU rule. Under ORC 519.02 a township may regulate the location, size, and uses of buildings and the density of population in its unincorporated territory. Whether an ADU is a permitted use, and its size, setbacks, owner-occupancy, and parking rules, is set by whichever municipality or township you live in. Any ADU is still a dwelling and must meet the Ohio Residential Code, enforced locally.

Violations & Fines

Building or renting an ADU not permitted under your local zoning is a municipal or township zoning violation, enforced by your city, village, or township, not the county. Penalties, stop-work orders, and removal orders are set by local law.

Frequently Asked Questions

Does Montgomery County allow ADUs?

Montgomery County has no ADU zoning. Whether an ADU is allowed is set by your city, village, or township under Ohio home rule. Check with your local zoning or building office for size, setback, and permit rules.

What law lets townships regulate ADUs?

Ohio Revised Code Chapter 519 lets township trustees zone unincorporated land, including the location, size, and uses of buildings. Cities and villages zone their own limits separately. The county does not zone incorporated areas.

Sources & Official References

Other rules in Montgomery County

Shed & Carport RulesSome Restrictions Noise Ordinances: Aircraft NoiseSome Restrictions Noise Ordinances: Decibel LimitsSome Restrictions Noise Ordinances: Vehicle NoiseSome Restrictions Noise Ordinances: Amplified Music & Outdoor SoundSome Restrictions Noise Ordinances: Leaf Blower RulesSome Restrictions Noise Ordinances: Barking DogsSome Restrictions

All Montgomery County rules

How Montgomery County compares: Easiest Cities to Build an ADU·Compare Montgomery County to another location·View the Ohio accessory structures overview

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ADU Rules in Cities Across Montgomery County

Dayton, OH