County · Delaware
ADU rules in New Castle County
These are the primary sources for accessory dwelling unit regulations in New Castle County: the county's own zoning code, planning department pages, and permit guides. Start here before talking to anyone: the rules below are what your permit reviewer will apply.
Unincorporated areas only
County zoning applies only outside city limits. If your property is inside a city or town, that municipality's own ADU ordinance governs instead, even though it sits within New Castle County.
Find your city's rules in DelawareADU regulations
- newcastlede.govOfficial sourceVerified July 2026https://www.newcastlede.gov/DocumentCenter/View/420/Accessory-Dwelling-Unit-Permit-Requirements
- library.municode.comOfficial sourceVerified July 2026Code of Ordinances §40.03.410https://library.municode.com/DE/New%20Castle%20County/CODES/Code_of_Ordinances?nodeId=CH40UNDECO_ART3USRE_S40.03.410ACUSRE
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Zoning codes change. If a link is dead or New Castle County has updated its ordinance, report it and we'll verify against the official source.
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