New Castle County, DE Accessory Structures: ADU Owner Occupancy (2026)
Key Facts
- ADUs per lot
- One per single-family lot
- Occupancy proof
- Signed affidavit required
- Deed filing
- Recorded before permit issues
- Rentable units
- Only one unit at a time
- Parking
- One extra off-street space
Summary
New Castle County requires ADU owners to live in either the main house or the accessory unit, backed by a signed affidavit and a deed restriction recorded with the Recorder of Deeds before a building permit issues.
4. The property owner shall occupy and reside in either the principal dwelling unit or the ADU as his or her principal legal residence. An affidavit (available from the Department) of owner occupancy shall accompany the application for a building permit for the ADU.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Ordinances: Supplement 5).
Full Breakdown
Under Code § 40.03.410.I, New Castle County allows one accessory dwelling unit per single-family detached lot, but only if the property owner actually lives in either the principal house or the ADU as a full-time residence. The Department of Land Use requires a signed owner-occupancy affidavit with the ADU building permit application, plus a document recorded in the New Castle County Recorder of Deeds confirming that residency condition runs with the property. Only one of the two units can be rented out at a time, an extra off-street parking space is required, and if the ADU is rented it must be registered under the Chapter 19 rental licensing program before occupancy. This is county zoning, applying in unincorporated New Castle County; Wilmington and Newark run their own separate zoning and ADU rules.
Violations & Fines
Renting the ADU without the required occupancy affidavit or Chapter 19 rental registration is a Code violation; the county can deny, revoke, or refuse to renew the building or occupancy permit.
Frequently Asked Questions
Can I rent out both the main house and the ADU in New Castle County?
What paperwork does New Castle County require before an ADU building permit issues?
Sources & Official References
Other rules in New Castle County
Compare New Castle County to another location·View the Delaware accessory structures overview
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