ADU laws in Delaware

In plain words

Delaware has no statewide law that makes towns or counties allow accessory dwelling units (ADUs). An ADU is a small second home on the same lot as a house. Examples are a garage apartment, an in-law suite or a backyard cottage.

Zoning is the set of local rules that controls what you can build on your land. In Delaware, the three counties write zoning for land outside town limits. Each city or town writes its own. So the answer depends on exactly where your property sits.

Rules vary a lot. Outside towns in Sussex County, county staff can approve one ADU without a public hearing. It can be up to 1,000 square feet, on a lot of at least 10,000 square feet. Outside towns in New Castle County, the owner must live on the property. A detached ADU there needs at least half an acre. In Dover, ADUs are mostly limited to special planned neighborhoods.

Lawmakers tried to change this. Bills in 2024 and 2025 would have made every local government allow one ADU "by right." By right means approval without a public hearing if the plans meet the rules. Neither bill passed.

In July 2026, Delaware passed the Housing for Every Delawarean Act. It does not legalize ADUs directly. Counties and towns over 2,000 people must write affordable housing plans. Those plans must include allowing a mix of home types without special permits, and ADUs are named as one type. Each plan becomes part of the place's comprehensive plan, its long-range plan for land use. Plans are updated on a multi-year cycle, so changes will roll out over several years.

Check your local code and any homeowners association (HOA) rules first. Build only if local rules and your property allow it.

The rules at a glance

What to do next

1. Find out whether your property is inside a city or town or on unincorporated county land, using your county's parcel search or tax bill.
2. Read the local ADU section (Sussex County Code § 115-20A(15); New Castle County UDC § 40.03.410(I)) and check lot size, owner-occupancy and parking rules.
3. Call the local planning or zoning office and ask whether an ADU is approved by staff or needs a hearing, such as a special use exception or variance.
4. Confirm sewer or septic capacity early; both Sussex and New Castle Counties tie ADU approval to it.
5. Read your HOA covenants and deed restrictions, which Sussex County says take precedence over its ADU rules.
6. If you live in a DSHA pilot town (Bridgeville, Dover, Georgetown, Laurel, Lewes, Milford, Newark, Rehoboth Beach) or Sussex County, watch for proposed zoning changes and public comment periods.

Grants, loans and tax breaks

• DSHA Zoning and Land Use Reform Pilot Program (SJR 8): Free consultant help for local governments, not homeowners. Announced February 26, 2026 for Bridgeville, Dover, Georgetown, Laurel, Lewes, Milford, Newark, Rehoboth Beach and Sussex County; each picks reforms from a menu that includes allowing ADUs as a permitted use in residential zones. Program page

What your town still decides

No Delaware statute requires local governments to allow ADUs. New Castle, Kent and Sussex Counties zone the unincorporated land, and each incorporated city and town zones its own land, so the rules change at town lines. Two state actions push in the ADU direction without mandating it: (1) Senate Joint Resolution 8 (signed August 21, 2025) had the Delaware State Housing Authority (DSHA) fund consultants to help nine volunteer jurisdictions rewrite zoning, with allowing ADUs as one menu option; (2) the Housing for Every Delawarean Act (signed July 13, 2026) makes counties and towns over 2,000 people adopt affordable housing plans, built with DSHA, that include authorizing a mix of housing types including ADUs without special permits. Those plans arrive with each jurisdiction's next comprehensive plan; a place adopting its next plan before February 1, 2027 can wait until its next 5-year review. In practice, a homeowner's answer still comes from the local zoning code and the local planning office.

Examples of local rules

• Sussex County (unincorporated areas): Ordinance 3027 (June 25, 2024) renamed garage/studio apartments as ADUs. One ADU is approved by the planning director without a Board of Adjustment hearing. It can be attached, detached or a converted basement, up to 1,000 sq ft and no more than half the house's floor area, with at least one parking space. It must meet setbacks, sit behind the house on lots under 3 acres, and the lot must be at least 10,000 sq ft. A signed survey is required. HOA and deed rules still control. Source
• New Castle County (unincorporated areas): Unified Development Code § 40.03.410(I) allows one ADU per single-family detached lot, inside the house or as an attached addition. Ordinance 24-087 (signed October 4, 2024) cut the minimum lot for a detached ADU from 2 acres to half an acre, removed the countywide cap on ADU permits, and allowed small homes as ADUs; a detached ADU must meet the house's setbacks. The owner must live in one unit (affidavit plus a recorded document), only one unit may be rented, one extra off-street parking space is required, rentals must be registered, and sewer or septic capacity must be adequate. Source
• City of Dover: Dover's zoning code mentions ADUs only in two special districts: the Traditional Neighborhood Design (TND) zone, which allows one ADU with a detached single-family house, and the Planned Neighborhood Design option, where the Planning Commission may approve a limited number of ADUs as part of the overall plan. Dover is one of the nine jurisdictions in DSHA's 2026 zoning reform pilot. Source
• City of Wilmington: A search of Wilmington's online code (October 2026) returned no section using the terms 'accessory dwelling unit' or 'accessory apartment'. Any second unit would fall under the city's general zoning rules for dwellings, so ask the city's zoning staff before planning one. Source

What we’re still confirming

• Whether the 2026 Housing for Every Delawarean Act makes every covered town or county allow ADUs, or only a mix of housing types, will depend on how the state housing authority reviews local plans.

Laws, bills and citations

This is general information, not legal advice. Your town, village, city or county decides what can be built on your property. If something here looks out of date, email the team.