Wilmington ADU permit requirements
Last reviewed: June 22, 2026
Quick answer
Permitting an accessory dwelling unit (ADU) in Wilmington, Delaware means pulling a building permit from the local authority that issues it. ArchPermit tracks 12 source-cited requirements (8 required, the rest conditional) for this jurisdiction. Submittals go through Land Use & Planning intake (email/in-person) + MUNIS Citizen portal. These requirements were last reviewed June 22, 2026; confirm the exact forms and fees with the local permitting authority.
A source-cited checklist of what an ADU (accessory dwelling unit) permit package needs in City of Wilmington. Every item links to its authoritative source; items that vary are flagged to confirm locally.
Wilmington, Delaware has no ADU provisions in its zoning (Chapter 48). A full-code search for 'accessory dwelling unit' returns no hits, and 'accessory building' is defined as a non-dwelling subordinate building. There is no by-right ADU pathway; a second dwelling unit would have to fit a district that allows two-family dwellings (e.g. R-2) or go through the Zoning Board of Adjustment. The submittal set below is the general residential building-permit package (2018 IRC; § 48-36 requires scaled plans in duplicate, a Certificate of Zoning, and ultimately a Certificate of Occupancy). NOTE: most 'Wilmington ADU' information online is Wilmington, NORTH CAROLINA, a different state whose figures do not apply here. Confirm any ADU initiative with Land Use & Planning.
- 3 Sets of Drawings, Sealed by a DE-Registered Design Professionalrequired
Architectural + structural drawings (and MEP/gas/fire protection as applicable), sealed & signed by a Delaware-registered design professional.
source · reviewed 2026-06-22 - Building Permit Application (signed)required
The base application form, completed and signed by the applicant.
source · reviewed 2026-06-22 - Contractor/Subcontractor Licensing (City + State)required
All trades must hold City of Wilmington and State of Delaware licenses.
source · reviewed 2026-06-22 - Copy of Signed Contractrequired
A copy of the signed contract between the licensed contractor and the responsible party.
source · reviewed 2026-06-22 - Lines & Grades Planrequired
A One- & Two-Family new-construction submittal item.
source · reviewed 2026-06-22 - Mechanical / Plumbing / Electrical Plans (sealed)required
MEP plans signed & sealed by a DE-registered engineer, with the architectural & structural drawings.
source · reviewed 2026-06-22 - RESCheck (energy code compliance)required
Energy-code compliance documentation for new residential construction.
source · reviewed 2026-06-22 - Scaled Plans in Duplicate (zoning)required
Per § 48-36: plans drawn to scale ≥1/8" per foot, in duplicate, showing lot shape/dimensions, exact size/location of every building, intended use, and number of dwelling units.
source · reviewed 2026-06-22 - Approvals from Applicable City Departmentsconditional
Public Works / Water and other clearances, not required at intake but gating before issuance.
source · reviewed 2026-06-22 - Certificate of Occupancy (at completion)conditional
Required before lawful use/occupancy (§ 48-37), preceded by a Certificate of Zoning (§ 48-35).
source · reviewed 2026-06-22 - Fire Marshal Approval / Residential Sprinkler Submittalconditionalverify locally
'Comply with Fire Marshal's requirements (not required at intake)'; confirm the residential-sprinkler scope with the Fire Marshal.
source · reviewed 2026-06-22 - Site Plan / Plot Plan / Surveyconditional
Required for additions/exterior alterations; the § 48-36 plot info is required generally.
source · reviewed 2026-06-22
Wilmington ADU permit questions
- Do I need a permit to build an ADU in Wilmington?
- Yes. An accessory dwelling unit (ADU) in Wilmington requires a building permit. ArchPermit tracks 12 cited requirements for this jurisdiction (8 required, the rest conditional). Always confirm the exact forms, fees, and code edition with the local permitting authority that issues the permit.
- What does an ADU permit package require in Wilmington?
- Core required items include: 3 Sets of Drawings, Sealed by a DE-Registered Design Professional; Building Permit Application (signed); Contractor/Subcontractor Licensing (City + State); Copy of Signed Contract; Lines & Grades Plan; Mechanical / Plumbing / Electrical Plans (sealed), plus 2 more. Each requirement links to its authoritative source, and nothing is permit-ready until an independent licensed professional reviews and seals it.
- How are ADU permits submitted in Wilmington?
- Wilmington accepts permit submittals via Land Use & Planning intake (email/in-person) + MUNIS Citizen portal. ArchPermit prepares a draft package you can submit there after a licensed architect reviews and seals it.