How building permits work in Delaware
These rules apply across Delaware. Each local guide above covers what is specific to that city, town, township or county: its building department and contacts, local rules, fees and inspections.
Who holds the code and the state reviews
The state layer is narrow but firm. Under Delaware law the State Fire Marshal must review plans for all new buildings and additions, for any building undergoing a change of occupancy, and for any part of a building damaged by fire, explosion or other cause — with two exceptions that matter: buildings used wholly as dwellings of no more than two families, and buildings used wholly for farming. That means almost every commercial project in Delaware carries a state plan review alongside its county or municipal permit, and almost no ordinary house does. Electrical work is separately regulated at state level, and licensed electrical inspection agencies rather than the county carry out the inspections.
Delaware has no statewide building code, but several construction codes are set at state level and every county and town must enforce them: the plumbing code (16 Del. C. 7904), the mechanical and fuel gas codes adopted by the State Board of Plumbing, Heating, Ventilation, Air Conditioning and Refrigeration Examiners (24 Del. C. 1806), the energy code (16 Del. C. 7602; counties must adopt each new state edition within 12 months) and the State Fire Prevention Regulations. Electrical work everywhere must be inspected by a state-licensed inspection agency (24 Del. C. 1420).
The fire marshal’s plan review also covers sprinkler and alarm systems, fuel tank installations, subdivision and site plans, and tenant fit-outs and renovations. Four cities — Dover, Newark, New Castle and Wilmington — have their own fire marshal, who carries out that review inside the city (16 Del. C. 6612). In Sussex County, and in other places with no local plumbing programme, plumbing permits and inspections come from the Division of Public Health.
Which authority holds the code for your address
This is the first question on any Delaware project and it has three possible answers. In an unincorporated area the county is the building authority. In a municipality that runs its own building department — the larger cities do — the municipality issues the permit and the county does not. And in a number of smaller incorporated towns the county enforces the building code while the town handles zoning, so a project needs both and neither office can answer for the other. Because the three counties are on different code editions with different amendments, the answer also determines which standard the work is built to.
The state reviews that run alongside the permit
Three state processes commonly run in parallel with a Delaware building permit. The State Fire Marshal's plan review is required on the categories set out in statute, is charged on the estimated cost of construction against a published formula, and must be approved before the work it covers proceeds. Electrical inspection is carried out by licensed inspection agencies rather than by the county or the town. Sediment and stormwater plans go to the delegated agency for the site — the Kent or Sussex Conservation District, New Castle County, the New Castle Conservation District, or Newark, Middletown or Wilmington for their own areas — while wetlands, subaqueous-lands and beach building-line approvals come from DNREC.
Business and trade licences
Delaware does not issue a general contractor competency licence. Contractors instead need a Delaware contractor business licence from the Division of Revenue (30 Del. C. 2502) and must register with the Department of Labor’s Office of Contractor Registration before starting work (19 Del. C. 3604); since January 2026 the Department can also suspend a contractor who uses unregistered subcontractors. Many permit offices ask for the business licence number on the application, and some municipalities require their own local licence on top. Trade competency is regulated at state level: electricians are licensed through the State Board of Electrical Examiners, plumbers and HVACR contractors through the State Board of Plumbing, Heating, Ventilation, Air Conditioning and Refrigeration Examiners, and fire protection contractors by the State Fire Marshal, whose licence number must appear on a fire protection plan review application. Homeowners may do their own wiring or plumbing in their own home with the relevant homeowner permit.
Trade work in Delaware is regulated at state level even where the building code is not. Electricians, plumbers and fire protection contractors hold state licences, and electrical inspection is carried out by licensed agencies rather than by the authority that issued the building permit.