Middlesex County, NJ Accessory Structures: ADU Rules (2026)

Under the New Jersey Municipal Land Use Law (N.J.S.A. 40:55D), zoning belongs to each municipality, and Middlesex County's 25 municipalities each set their own ADU rules. The Middlesex County Planning Board's role under N.J.S.A. 40:27-1 et seq. is limited to county master planning and review of subdivision/site plan applications affecting county roads or facilities — it does not approve individual ADU applications. Middlesex County municipalities generally treat accessory apartments restrictively: typical minimum lot sizes of 10,000 to 20,000 sq ft in residential zones that permit them, unit size limits of roughly 30-40% of the primary dwelling or 800-1,000 sq ft maximum, and owner-occupancy requirements. New Brunswick (university-driven housing demand), Edison Township, and Woodbridge Township have not adopted dedicated ADU ordinances and would require a use variance from the Zoning Board of Adjustment under N.J.S.A. 40:55D-70(d). As of May 2026, S1786 is pending in the Senate Community and Urban Affairs Committee but has not been enacted. Property owners should check the specific municipal zoning ordinance on eCode360 or contact the local Zoning Officer.