Mahwah, NJ Accessory Structures: ADU Rules (2026)

Mahwah's land use program is set out in Chapter 24 of the Township Code, adopted under the New Jersey Municipal Land Use Law (N.J.S.A. 40:55D-1 et seq.). Under Section 24-4.1(d), accessory apartments are permitted as a conditional accessory use in all residential zoning districts, subject to the standards in Section 24-6.1(j). Those standards establish that a maximum of one accessory apartment is permitted for each existing or future single-family residence; the minimum floor area is 400 square feet and the maximum floor area is 800 square feet; in no instance may the apartment exceed 30% of the habitable living space of the dwelling; a maximum of three occupants per apartment is permitted; and the building must be owner-occupied at all times. Section 24-6.1(j) further specifies that, after July 1, 1997, no new affordable accessory apartments shall be created. Because accessory apartments are conditional uses, applicants must obtain conditional use approval from the Planning Board (or Zoning Board of Adjustment, where applicable) under the Municipal Land Use Law. New Jersey Uniform Construction Code permits (N.J.A.C. 5:23) are required for any construction work to create or convert the apartment, including separate egress, smoke and carbon monoxide alarms, and any required electrical, plumbing, or mechanical work.