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