Smithtown, NY Accessory Structures: ADU Rules (2026)

Section 322-82C(23) of the Building Zone Ordinance lists accessory apartment dwelling units as a special exception use, requiring Board of Appeals approval under the general standards in Section 322-94G before any unit is created. The dimensional and safety standards are specific: the apartment cannot be located on the first floor of the building, and it cannot contain more than two bedrooms, keeping units small and secondary to the ground-floor use below. A suitable, safe, and pedestrian-attractive means of access to the unit is required, separate from the building's principal entrance, and every unit must have a smoke detector, fire alarm, or sprinkler system installed.

Parking is handled flexibly: the Board applies the Town's general off-street parking standards, but it may accept fewer on-site spaces if the applicant shows a public parking lot lies within 200 feet walking distance, and even a reduction under the central-business-district provisions of Section 322-83B cannot cut required stalls below 60% of the normal standard. Importantly, this is not a residential backyard ADU program: as set out in Section 322-82C(23)(f), covered separately, an accessory apartment may only be created on premises that already contain a qualifying commercial use, so a homeowner on an ordinary single-family lot cannot use this section to add a rental unit.

The Board of Appeals special exception process means each application is reviewed individually, and any condition the Board attaches becomes an enforceable requirement of the permit.