New Castle County, DE Building Setbacks & Zoning: Setback Rules (2026)

New Castle County building setbacks are established in the Unified Development Code (UDC), primarily Article 40, and vary by zoning district. Common residential districts and typical setback requirements: S (Suburban): 40 ft front, 15 ft side, 40 ft rear on lots 1 acre+; NC5: 25 ft front, 10 ft side, 30 ft rear; NC6a: 25 ft front, 10 ft side combined minimum, 30 ft rear; NC6b: 20 ft front, 5 ft side, 25 ft rear for smaller lots; NC10: 20 ft front, 5 ft side, 20 ft rear in compact patterns; NC21: urban infill with reduced setbacks. Commercial and mixed-use districts have different rules. Corner lots are treated as having two front yards, with a primary front yard along the longer street frontage and a secondary setback along the shorter. Accessory structures (sheds, detached garages) have reduced setbacks, typically 3 to 5 ft from side and rear lines if under 150 sq ft. Eaves and architectural features may project up to 2 ft into setbacks. Variances require application to the NCC Board of Adjustment (UDC Article 40, Section 30.300) with a public hearing. Pool decks, HVAC units, and generators have specific setback rules. Floodplain and riparian buffer setbacks (Brandywine Creek, Christina River, Red Clay Creek) add layers under the Chesapeake Bay and Coastal Zone protections.