Union County, NJ Building Setbacks & Zoning: Lot Coverage Limits (2026)

Lot coverage regulation in Union County combines zoning-based building/impervious coverage caps with stormwater management requirements under NJ DEP rules. Elizabeth Land Development Code Chapter 20 establishes R-1 maximum building coverage of 35% with total impervious coverage (buildings plus driveways, patios, walkways) capped at 60%; R-2 building 40%, total 65%; commercial zones vary. Westfield Land Use Ordinance §13.03 establishes tight suburban caps: RS-24 building 20%/impervious 30%, RS-18 25%/35%, RS-12 30%/40%, RS-8 30%/45%. Summit RA district 25% building/35% impervious; RB 30%/45%. Cranford Chapter 255 typical suburban ratios. NJ Stormwater Management Rules (N.J.A.C. 7:8-5) impose additional requirements on major development disturbing 1+ acres or adding 1,000 sq ft of impervious, and 'minor development' adding 0.25+ acres or 400+ sq ft of new impervious may trigger municipal stormwater review. Elizabeth, Linden, Plainfield, Rahway, and Cranford all implement stormwater ordinances under their municipal separate storm sewer system (MS4) permits. The Rahway River and Elizabeth River watersheds are subject to the FEMA flood hazard area rules and NJ Stormwater Best Management Practices Manual. Permeable pavers typically receive 50% credit in impervious calculations in Union County municipalities. Reducing existing impervious below zone maximum may earn offset credits under some local stormwater programs.