Building permits, zoning and land rules in New Castle County, Delaware

Unincorporated New Castle County requires a building permit for new buildings, alterations and most repairs, issued and enforced by the Department of Land Use under County Code Chapter 6¹. Work is exempt only if the county's exempt-work list names it; if a project is not on that list, assume a permit is required¹. The county has adopted the 2024 building, residential, existing-building, and swimming-pool codes; the 2018 energy code; and the 2021 mechanical, fuel-gas, and plumbing codes¹⁵. After permit issuance, the county inspects applicable stages of work, and construction cannot pass an inspection point without approval². A final inspection and Certificate of Occupancy or Use are required before a permitted building can be occupied³. For a new single-family home, the building permit costs $12 per $1,000 of valuation and the occupancy certificate costs $60¹³. An owner-occupier may act as their own new-home builder only under a one-time exemption approved by the Code Official; the owner cannot put an unlicensed person in charge and remains responsible for compliance¹⁰.

The New Castle County Department of Land Use is the county's building department, handling permits, planning and zoning from the New Castle County Government Center, 87 Reads Way, New Castle, DE 19720³. Planning & Permits can be reached at 302-395-5400, and Code Enforcement at 302-395-5555³. The office is open Monday through Friday, 8 a.m. to 4 p.m³.. Applications and plans for construction in unincorporated areas can be submitted electronically, and typical documentation includes lines-and-grades, drainage, erosion-control, sewage-disposal, building, mechanical and plumbing documents¹⁶. If your land sits inside an incorporated town rather than unincorporated New Castle County, that municipality issues its own permits instead¹⁶. Septic and well permits still come from DNREC at every address, town or not⁸.

New Castle County zones unincorporated land under its Unified Development Code, which controls zoning districts and the use, bulk, design, and location of land and buildings³. The same code regulates land subdivision, so splitting or developing a tract may require Department of Land Use review and other approvals³. Lot standards are district-specific: for example, the NC10 residential district requires at least 10,000 square feet³. Commercial-stable rules are also specific: SR and SE parcels need at least 5 acres and 300 feet of width, while S parcels need at least 3 acres and 200 feet; their street, side, rear, and height limits differ¹⁷. Inside Wilmington, Newark, Delaware City and Townsend, the town's own zoning code applies instead of the county's^4,5,6,7. The county sets no single minimum house size for new homes that we could confirm; the one fixed floor-area figure in its code applies to converting an old single-family house into apartments, where each apartment must be at least 800 square feet¹⁴. Confirm the parcel's district before planning a home, stable, RV use, tiny home, or lot split³.

Septic systems in New Castle County are a state matter: Delaware DNREC administers the onsite-wastewater approval process⁸. Before applying for a new or replacement system permit, a Class D soil scientist must prepare the site evaluation; a licensed Class B designer handles a gravity system, while a Class C designer handles an engineered or pressure-dosed system; installation requires a Class E contractor¹⁸. Only about 12.4% of New Castle County soils lack severe limitations for a conventional drain field, so determine septic feasibility before relying on an undeveloped parcel¹⁹. Installations and repairs are inspected unless DNREC waives a qualifying pre-cover inspection, and a sale generally requires pumping and inspection unless an exception applies¹⁸. Off-grid does not mean untreated: wastewater fixtures must connect to a central system or a DNREC-approved onsite system, though DNREC may approve alternative technology that provides equivalent treatment²⁰. DNREC's Division of Water answers septic questions at 302-739-9947 and well-permit questions at 302-739-9944²¹.

New Castle County treats a tiny home as an accessory dwelling unit, not as a way around zoning: it can be added to a qualifying single-family lot if it meets County Code's ADU standards, only one ADU is allowed per lot, and the owner must live in either the main house or the ADU as their primary residence¹¹. A detached tiny home or ADU needs at least half an acre of lot, plus its own building permit and Certificate of Occupancy, before anyone can live in it²². Delaware's housing code uses an occupant-based floor-area standard rather than one fixed minimum home size: at least 150 square feet for the first occupant and 100 square feet for each additional occupant²³. Manufactured or modular housing that does not qualify as a single-family dwelling is limited to a manufactured home park or agricultural-zoned land and requires a state-licensed installer and county use permit¹². We could not confirm the current rule for residential RV occupancy or ordinary temporary camping on private land; ask the Department of Land Use before relying on either use³.

1. Confirm zoning and whether subdivision review applies. Use the county's maps or request a zoning certification, and ask the Department of Land Use before splitting or developing a tract³.
2. Resolve wastewater and water. Obtain the soil evaluation and licensed septic design needed for a DNREC permit; if using a well, have a licensed well contractor submit the DNREC application^9,18.
3. Submit the county application and plans. Electronic filing is available, and typical documents cover lines and grades, drainage, erosion control, sewage disposal, building, mechanical, and plumbing work¹⁶.
4. Budget for approvals. A new single-family permit costs $12 per $1,000 of valuation, plus a $60 occupancy-certificate fee and a zoning fee equal to 10% of the building-permit fee, subject to a $21 minimum and $145 maximum¹³.
5. Clear access and floodplain issues. A new or modified driveway may require a DelDOT entrance permit, while regulated flood-hazard development must meet county floodplain rules^24,25.
6. Schedule each required county inspection and do not build past an inspection point without approval². After the final inspection and correction of outstanding issues, obtain the Certificate of Occupancy or Use before moving in³.

New Castle County has about 1,357 people per square mile, and the nearest city of 100,000 or more is about 42 miles from the county center¹⁹. Only about 12.4% of county soils lack severe limitations for a conventional septic drain field, so establish septic feasibility before buying outside a sewer service area¹⁹. If the parcel needs a well, budget for a DNREC permit, a licensed well contractor, and contamination review of the proposed location⁹. For sewer, contact the county's drafting department to learn whether a connection is feasible; the county does not own or maintain water lines, so ask the local water company about water service²⁶. Check flood maps because regulated flood-hazard development must comply with county floodplain rules²⁵. Confirm legal driveway access because a new or modified driveway may require a DelDOT entrance permit²⁴. Typical property taxes are about 0.7% of value, with a median annual bill near $2,444¹⁹.