Pole barns and barndominiums in New Castle County, Delaware.

Outside incorporated towns, building permits come from the New Castle County Department of Land Use at the New Castle County Government Center, 87 Reads Way, New Castle, DE 19720. The Permits/Inspections/Planning line is (302) 395-5400, Code Enforcement is (302) 395-5555, and the office is open Monday to Friday, 8 a.m. to 4 p.m., with applications filed online through eApply/ePlans. Under 9 Del. C. § 2515, the county building code does not apply inside municipalities unless the county provides that service there. The building code is Chapter 6 of the County Code and zoning is the Unified Development Code (Chapter 40); we confirm the edition in force with Land Use before drawings are final.

For a garage, pole barn or other accessory building, the county’s residential addition and accessory structure checklist (revised November 2025) asks for a signed and sealed plot plan of existing and proposed improvements, building plans and a licensed contractor. Buildings of 480 square feet and larger also need a Lines and Grades plan sealed by a Delaware-licensed engineer or surveyor. The county’s shed permit packet notes that a homeowner cannot get the permit by listing a hired contractor; the contractor pulls it. On the county’s fee form (revised July 2019), the permit review fee is $12 per $1,000 of valuation with a $60 minimum, garages are valued at $16 per square foot and the bundled fees carry a $142 minimum, so confirm current fees with Land Use.

State law treats farm buildings differently. Under 9 Del. C. § 2515, the county building-code chapter does not apply to a building or structure devoted to agricultural use, and 9 Del. C. § 2601(b) bars county zoning regulations from agricultural land and structures. A structure qualifies if the land is farmland-assessed under § 8335, is in an Agricultural Preservation District, operates under a nutrient-management or agricultural-waste plan while producing plants or animals for sale, or is in a federal soil-conservation program. The county’s 2023 requirement sheet lists a $50 Certificate of Use for Agricultural Purposes, which needs a plot plan, building plans, Conservation District approval and proof of agricultural use under 9 Del. C. § 8333.

Check the flood maps before placing any building. County floodplain rules, as published in its administrative procedures, require 18 inches of freeboard (UDC 40.10.320 E, also adopted in Chapter 6), hold construction in the Limit of Moderate Wave Action to coastal high-hazard (VE) standards, prohibit net fill and require compensatory storage, and bar replacing or substantially improving structures in the floodway. A 2011 University of Delaware analysis put 67 square miles of the county, 16% of its land, in the mapped 100-year floodplain, with 2,431 structures, 1,007 of them in the Christina River watershed. County documents change, so we confirm each of these requirements with Land Use before we file.