ADU Pass
Delaware County
ADU Pass helps homeowners in Delaware County, Ohio navigate the permit paperwork for building an accessory dwelling unit. We cover 9 cities and 11 ZIP codes in this county.
Map
County ADU details
County ADU ordinance
Delaware County, Ohio (north-Columbus suburban / exurban county on the Olentangy River; ~232,000 residents as of the 2024 ACS estimate, by some measures the fastest-growing or among the top-three fastest-growing counties in Ohio for the 2010-2024 decade; county seat City of Delaware; eighteen townships including Berkshire, Berlin, Brown, Concord, Delaware, Genoa, Harlem, Kingston, Liberty, Marlboro, Orange, Oxford, Porter, Radnor, Scioto, Thompson, Trenton, and Troy; incorporated places City of Delaware (county seat), City of Powell, City of Westerville (mostly in Franklin County with a Delaware-County remainder), Village of Galena, Village of Ostrander, Village of Sunbury, Village of Shawnee Hills, Village of Ashley, and unincorporated Lewis Center / Polaris CDP) does NOT operate a unified countywide zoning ordinance for unincorporated territory and has not adopted county-tier zoning under O.R.C. Chapter 303. Ohio is a home-rule state under Article XVIII of the Ohio Constitution and Dillon's Rule otherwise; O.R.C. § 303.02 permits a board of county commissioners to adopt county zoning subject to a referendum, but Delaware County has never put a countywide zoning question to its voters (Lake County is the canonical Ohio county that does operate county-tier zoning). Zoning in unincorporated Delaware County is therefore performed township-by-township under O.R.C. Chapter 519 (Township Rural Zoning), and the Delaware County Regional Planning Commission (DCRPC) provides advisory subdivision and plat review under O.R.C. § 711.10 plus county-level coordination. Every one of Delaware County's eighteen townships HAS adopted township zoning (a notable contrast with rural Ohio counties where many townships are unzoned); this is a consequence of Columbus-driven development pressure since the 1990s. ADU regulation in unincorporated Delaware County is thus set township-by-township; the County's land-use role is limited to subdivision/plat advisory review, addressing, the County Engineer (county roads, drainage), the General Health District (private septic and water), the Delaware Soil and Water Conservation District (erosion and sediment), and the County Auditor (assessment). The City of Delaware, City of Powell, the Delaware-County portion of Westerville, and the villages of Galena, Sunbury, Ostrander, Ashley, and Shawnee Hills all zone independently under their charters or home-rule grants.
County assessor
Assessment policy: The Delaware County Auditor (George Kaitsa, 2026) is the elected property-assessment authority under O.R.C. § 5713.01. Ohio assesses real property at 35% of true value (O.R.C. § 5713.03). New ADU construction is added to the parcel record on the next regular revaluation cycle (Ohio runs a triennial-update / sexennial-reappraisal cycle under O.R.C. § 5715.24; Delaware County's most recent full reappraisal was tax year 2023 with the next triennial update due tax year 2026) and reassessed at true value as of January 1 following completion. The Ohio Owner Occupancy Credit (O.R.C. § 323.151 et seq.) provides a 2.5% tax reduction on owner-occupied homestead; the Homestead Exemption (O.R.C. § 323.152) reduces taxable value by $25,000 for owners 65+ or totally and permanently disabled (income-qualified). An ADU that is rented separately may carve out a non-homestead component subject to standard assessment, while the host dwelling retains the Owner Occupancy Credit. Delaware County also administers Current Agricultural Use Valuation (CAUV) under O.R.C. § 5713.30 - § 5713.38; CAUV enrollment is significant in the northern townships, and an ADU built on a CAUV parcel can trigger a partial recoupment (rollback) if the dwelling reduces qualifying agricultural acreage. Under O.R.C. § 5713.17, the owner must notify the Auditor of any construction or improvement valued over $2,000. Delaware County saw exceptional valuation increases (median residential values up 25-40% county-wide) in the 2023 sexennial reappraisal driven by the south-county housing market; ADU additions in 2024-2026 are being captured on the triennial-update cycle.
County overlays (5)
Known county issues (5)
- other — Researchers should consult the specific township zoning inspector for any unincorporated parcel before assuming ADU permission or prohibition. Township ordinances are not centrally indexed at the county level; many townships publish ordinances on township websites with limited search facility, and the County Regional Planning Commission's role is advisory rather than authoritative. Southern townships (Orange, Liberty, Genoa, Berlin) tend toward suburban-residential frameworks that are restrictive on second dwellings; northern townships (Radnor, Thompson, Marlboro) tend toward agricultural-residential frameworks that are more permissive on accessory dwellings serving farm-family or caretaker uses.
- other — Researchers should not generalize ADU cost or feasibility across Delaware County. South-county feasibility is dominated by township zoning posture and utility tap fees; north-county feasibility is dominated by septic siting and CAUV considerations. The City of Delaware (county seat) is a hybrid: central utilities are available, but the city's zoning posture on ADUs is set by city ordinance, not township rule.
- other — Enumeration of Delaware County cities here includes both for fidelity to the highlights tree, but consumers should not attribute Westerville's full ~39,190 residents or Richwood's ~2,281 residents to Delaware County for population-weighted statistics. The Phase 8 cascade will dispatch Delaware-County-specific city-adu-check runs only for the seven cities actually centered in Delaware County (Delaware, Galena, Lewis Center, Ostrander, Powell, Radnor, Sunbury); Westerville and Richwood should be researched under their primary counties.
- other — ADU projects in Concord, Liberty, Delaware Township, City of Delaware, and Berlin Township along the Olentangy should plan for Scenic River program consultation and additional setback / riparian-buffer expectations. Big Darby Accord parcels in Scioto Township face stream setbacks and impervious-surface caps tighter than baseline township zoning. Floodplain mapping along all three Scenic / Accord systems is independently administered through NFIP.
- policy-review — Researchers should monitor the Ohio General Assembly for any future ADU preemption proposal; until one passes, Delaware County's ADU framework remains the patchwork sum of eighteen township resolutions plus eight municipal codes (City of Delaware, City of Powell, Westerville Delaware-County remainder, Galena, Sunbury, Ostrander, Ashley, Shawnee Hills).
Federal (United States) — ADU-relevant rules and programs
Federal ADU law
The United States has no federal statute that directly regulates accessory dwelling unit entitlement or design. Land-use authority over ADUs resides with states and local governments under the traditional police power. Federal engagement is limited to financing (Fannie/Freddie/FHA/VA/USDA), flood insurance (FEMA/NFIP), and discretionary housing programs (HUD), which are recorded in sibling sections of this file.
Federal financing programs
Federal housing-finance agencies and GSEs set nationwide underwriting rules that govern whether an ADU can be financed, appraised, and counted toward mortgage qualifying income. The relevant actors are Fannie Mae, Freddie Mac, FHA (HUD), VA, and USDA Rural Development.
Federal tax credits
There is no ADU-specific federal tax credit. ADUs may incidentally qualify for existing federal energy-efficiency and clean-energy tax credits when the ADU construction includes qualifying measures.
Federal housing programs
HUD administers several discretionary programs that can fund ADU-related activity at the grantee's election, but none is an ADU-specific program.