Unincorporated New Castle County, Delaware requires a building permit for a home, garage or other structure, issued by the county's Department of Land Use1. The county also has countywide zoning through its Unified Development Code, which sets districts, lot standards and permitted uses for unincorporated land2. Septic systems are a state matter: Delaware's DNREC designs, permits and inspects onsite wastewater systems statewide, not the county3. An owner can hold their own building permit rather than hiring a registered contractor4.
At a glance
- Building permit
- Required — issued by the Department of Land Use1
- Zoning
- Yes — countywide Unified Development Code2
- Septic (OSSF) permit
- Permitted by the state (DNREC), not the county3
- Owner-builder exemption
- Yes — an owner may hold their own building permit4
- Tiny home / ADU
- Allowed as an accessory dwelling unit, one per lot5
- Manufactured home
- Limited — only in a manufactured home park or on ag-zoned land6
- New single-family building permit fee
- $12 per $1,000 of valuation, plus a $60 C.O. fee7
- Property tax
- About 0.7% effective rate; median bill $2,444/yr89
Who to call
Building permits
New Castle County Department of Land Use
Building permits, zoning, code enforcement and land-use administration for unincorporated New Castle County
87 Reads Way, New Castle, DE 19720
Septic permits
Statewide septic (onsite wastewater) and well permitting for New Castle County and the rest of Delaware
Richardson and Robbins Building, 89 Kings Highway, Dover, DE 19901
Contact details are copied from each office’s official page and were checked against it on September 24, 2026.
Do you need a building permit in New Castle County, DE?
Unincorporated New Castle County requires a building permit for construction, issued and enforced by the county's Department of Land Use under County Code Chapter 61. The county has adopted current model codes as its local building standards: the 2024 International Building, Residential, Existing Building and Swimming Pool and Spa Codes, the 2018 International Energy Conservation Code, and the 2021 International Mechanical, Fuel Gas and Plumbing Codes10. For a new single-family home, the building permit itself costs $12 per $1,000 of valuation, and a Certificate of Occupancy adds $607. If you act as your own contractor rather than hiring one, New Castle County's code allows an individual to hold their own building permit4.
Who is the New Castle County building department, and how do you reach them?
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 1972011. Planning & Permits can be reached at 302-395-5400, and Code Enforcement at 302-395-555511. The office is open Monday through Friday, 8 a.m. to 4 p.m.11. 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 documents12. If your land sits inside an incorporated town rather than unincorporated New Castle County, that municipality issues its own permits instead13.
Does New Castle County have zoning?
New Castle County zones unincorporated land under its Unified Development Code, which creates and administers zoning districts and controls the use, bulk, design and location of land and buildings2. The county publishes a range of urban, suburban and special zoning districts, and confirming which one applies to your parcel — through the county's zoning maps or a zoning certification — is the real first step before you plan anything14. Because zoning applies here, minimum lot size, setbacks and building height for your parcel come from its specific zoning district rather than one countywide number. Delaware's statewide framework confirms this is how it works everywhere in the state: Delaware delegates zoning entirely to counties and municipalities, and there's no single statewide district schedule to fall back on15.
How do septic permits work in New Castle County?
Septic systems in New Castle County are a state matter, not a county one: Delaware's DNREC designs the statewide rules and administers permitting for every onsite wastewater treatment and disposal system, including in New Castle County316. Before you can even apply for a permit, a Class D soil scientist must complete a site evaluation, and a licensed system designer — Class B for a standard gravity system, Class C for an engineered or pressure-dosed one — must design it; installation itself must be by a licensed Class E contractor17. Only about 12.4% of New Castle County's soils have no severe limitations for a conventional septic drain field, so an engineered system is a real possibility on many parcels18. DNREC's Division of Water handles septic-system questions at 302-739-9947, and well permits at 302-739-9944, from the Richardson and Robbins Building, 89 Kings Highway, Dover, DE 1990119. The county still has a say in sewer instead of septic: sewer availability, connection fees and feasibility vary by location, and you'd contact the county's drafting department to check20.
Can you live in an RV or tiny home on your land in New Castle County?
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 residence5. 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 it21. Manufactured or modular housing that doesn't qualify as a single-family dwelling is more restricted: it can only go into a manufactured home park or onto agricultural-zoned land, needs a state installer license and a county use permit, and costs $200 to install as a single-section home or $300 as a double-section one6. No official rule found addresses ordinary temporary camping or RV living on private land the way it addresses tiny homes and manufactured housing, so call the Department of Land Use before you park an RV as a residence11.
Building a home in New Castle County: the steps, in order
- Confirm your zoning district. Before anything else, use the county's zoning maps or request a zoning certification from the Department of Land Use to see what your parcel allows1411.
- Design your septic system. A Class D soil scientist must evaluate your site, and a licensed Class B or C designer must design the system, before you can apply for a DNREC permit17.
- Apply for your DNREC septic permit and, separately, your county building permit; the Department of Land Use accepts electronic applications and plans covering lines-and-grades, drainage, erosion control, sewage disposal, building, mechanical and plumbing work12.
- Budget for fees. A new single-family building permit runs $12 per $1,000 of valuation, plus a $60 Certificate of Occupancy fee and a zoning permit fee of 10% of the building-permit fee (between $21 and $145)7.
- Check your driveway and floodplain status. A new or modified driveway may need a DelDOT entrance permit, and any development in a mapped flood hazard area must meet the county's floodplain-management rules in effect since February 20152223.
- Build, inspect, and get your Certificate of Occupancy. New Castle County enforces its own adopted building codes throughout construction, and your septic contractor's inspections must be reported to DNREC within 72 hours of each inspection1024.
What to check before you buy land in New Castle County
New Castle County is genuinely suburban, not remote: population density runs about 1,357 people per square mile, and a metro area is about 42 miles away at most2526. Only about 12.4% of the county's soils have no severe limitations for a conventional septic drain field, so a soil evaluation matters even here, especially outside sewer service areas18. Development in a mapped flood hazard area has required compliance with the county's floodplain rules since February 2015, so check FEMA flood maps before you commit to a parcel23. Typical property taxes run about 0.7% of value, with a median bill near $2,444 a year — noticeably higher than in Delaware's more rural counties89.
Watch-outs
- New Castle County's Unified Development Code, not one countywide number, sets your parcel's actual lot size, setback and height limits — confirm your zoning district with the Department of Land Use before you plan a build14.
- If your land sits inside an incorporated town rather than unincorporated New Castle County, that town issues its own permits and sets its own zoning instead of the county13.
Sources
- New Castle County Code Chapter 6 - Building Code (2026 county census)
- Zoning | New Castle County, DE (2026 county census)
- Delaware DNREC Septic Systems (2026 county census)
- New Castle County Code Chapter 6 - Building Code (2026 county census)
- NCC2050 Housing Initiatives, quoted and re-checked
- Manufactured Modular Home Permit Requirements, quoted and re-checked
- Single Family Dwelling Building Permit Requirements, quoted and re-checked
- Effective property tax rate: Bolthole Index county data
- Median property tax bill: Bolthole Index county data
- County Laws & Code | New Castle County, DE, quoted and re-checked
- New Castle County Department of Land Use (newcastlede.gov)
- Online Payments - Land Use, quoted and re-checked
- Zoning | New Castle County, DE, quoted and re-checked
- Zoning, quoted and re-checked
- 2020 Delaware Strategies for State Policies and Spending (Delaware statewide rule), quoted and re-checked
- Septic Systems, quoted and re-checked
- Septic Systems, quoted and re-checked
- Share of soils without severe limits for a conventional septic drain field (USDA SSURGO): Bolthole Index county data
- DNREC Division of Water (dnrec.delaware.gov)
- New Castle County Frequently Asked Questions — Public Works, quoted and re-checked
- Accessory Dwelling Unit Requirements, quoted and re-checked
- Land Use Home Improvements FAQs, quoted and re-checked
- Article 10 Floodplain Management Regulations, quoted and re-checked
- 7101 Regulations Governing the Design, Installation and Operation of On-Site Wastewater Treatment and Disposal Systems, quoted and re-checked
- Population density: Bolthole Index county data
- Distance to the nearest metro area: Bolthole Index county data
Written September 24, 2026 from the rules quoted below, each taken from an official source and re-checked by an independent reviewer. This is research, not legal advice: rules change, so confirm with the office before you buy or build.