Accessory Structures in New Castle County, DE (2026)
5 county-level rules, plus city-specific rules for 1 city in New Castle County, Delaware.
Verified from official government sources
ADU Rules
New Castle County allows one accessory dwelling unit per single-family detached lot, but the owner must live in the main house or the ADU, record a residency restriction with the Recorder of Deeds, and get a building permit before occupying it.
New Castle County ADU Permit Rules
Some RestrictionsNew Castle County Code § 40.03.410.I
Only one (1) ADU is permitted per single-family residential detached lot. The ADU may be constructed within the home or as an attached addition to the home... 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 bui...
ADU Owner Occupancy
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.
New Castle County ADU Owner-Occupancy Rule
Some RestrictionsNew Castle County Code § 40.03.410.I.4
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.
ADU Rental Restrictions
New Castle County caps ADU rentals at one unit per lot, requires owner-occupancy of the principal home or ADU, and makes rental ADUs register under Chapter 19 before occupancy.
New Castle County ADU Rental Restrictions
Some RestrictionsNew Castle County Code § 40.03.410(I)
Once an ADU is established, the primary structure shall not be used for apartment conversion and only one (1) of the dwelling units may be rented. ... Rental code registration. If the ADU is to be rented and prior to the issuance of a certificate of occupancy, the property owner shall register the ADU pursuant to the requirements of Chapter 19.
Shed & Carport Rules
Carports count as freestanding accessory structures under the Unified Development Code: they're barred from front, street, and side yard setbacks, must clear rear and side lot lines by at least 3 feet, and are capped at 20 feet in height.
New Castle County Carport Setback Rules
Some RestrictionsNew Castle County Code § 40.03.410
A.General standards. Unless otherwise provided in Subsections B. through M. of this Section, all accessory structures (e.g., detached garages, sheds, pergolas, and similar structures) shall meet the following standards:...2.Freestanding accessory structures shall not be located in any side yard setback or any required bufferyard.3.Freestanding accessory structures may be located in the rear yar...
Tiny Homes
New Castle County zones tiny homes as "small single-family detached dwellings," a defined use capped at under 750 square feet and allowed only as an ADU or inside a permitted pocket neighborhood.
New Castle County Tiny/Small Homes
Significant RestrictionsNew Castle County Code § 40.33.300
Dwelling, small single-family detached. A one (1) or two (2) story dwelling unit, designed for and occupied by not more than one (1) family and having no roof, wall or floor in common with any other dwelling unit. A. It has a minimum of four hundred (400) square feet of gross floor area and less than seven hundred fifty (750) square feet of gross floor area. B. It is of light-frame or masonry c...
Accessory Structures by City in New Castle County
1 cities in New Castle County have their own accessory structures rules. Each link goes to that city's dedicated page with code citations.
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