ADU rules in Babylon

A detached backyard cottage or garage conversion is not available in Babylon. The Town Code recognizes only an "accessory apartment," defined in section 153-13 as a self-contained dwelling unit "incorporated within a one-family dwelling," and section 153-18D adds that "No rental unit may be contained in any building or structure other than the main dwelling." Zoning reinforces this from the other direction: in the A, B and C Residence districts only one accessory building is allowed, capped at 500 square feet and 14 feet in height, and it may contain no interior plumbing fixtures and "no habitable or occupied space" (sections 213-71, 213-86 and 213-101). The zoning definition of "accessory building" in section 213-1 likewise says it is "not used for habitation." The residence-district permitted-use lists (for example section 213-61 in the A Residence district) allow a one-family dwelling and accessory buildings, and nothing else residential.

An internal accessory apartment inside an existing one-family house is allowed, but only with a special permit granted case by case by the nine-member Accessory Apartment Review Board after a noticed public hearing, not as of right. Section 153-14 gives the Board the power to hear "all accessory apartment permit applications" and to "impose such conditions and safeguards as it may deem appropriate," and section 153-16A requires a public hearing for every new application. The unit must be inside the main dwelling and no part of it may be in the cellar (section 153-18D); zoning section 213-250.4, added 8-7-2024 by L.L. No. 15-2024, separately bans kitchens in basements and states that "accessory apartments shall be prohibited in basements" in the AA, A, B, C and D Residence districts, which closes off the most common conversion. Section 153-18H also bars any application for three years after a certificate of occupancy is issued for the dwelling. Practically, an attic, second-floor or first-floor conversion is the path that remains.

Babylon caps the accessory apartment by room count rather than floor area. Section 153-18D provides that "Each dwelling unit must have a minimum of 350 habitable square feet" and that "One of the dwelling units shall be limited in size to a total of three rooms, not including a kitchen, a living room or bathrooms." The same subsection confines the unit to the main dwelling and keeps any part of it out of the cellar, and zoning section 213-250.4C(3) keeps it out of the basement as well. These size rules apply to new and pending applications, not to renewals or permit transfers, so older permitted apartments may be larger. There is no separate height or lot-coverage envelope for the apartment because it sits inside the existing house, which is governed by the underlying district's height, yard and building-area limits (for example 30 feet and 2 1/2 stories in the A Residence district under section 213-63).

Owner occupancy is the core condition and it is ongoing, not just a box ticked at application. Section 153-18A states flatly that "The dwelling must be owner-occupied," and section 153-15B terminates the permit immediately on the death of all owner-occupants named on it or "When all persons named on the permit are no longer owner-occupants." The owner is defined in section 153-13 as a natural person holding fee simple or a life estate of at least an undivided 50% interest, and section 153-18I sends any property owned wholly or partly by an entity to the rental permit process instead. The owner may live in either unit: section 153-18C says "The owner-occupant may reside in the accessory apartment." A buyer can take over the permit if the transfer paperwork is filed within 30 days of the transfer of title (section 153-15C through E). New York has no statewide ADU law that would preempt this; Town Law section 261 leaves zoning to the town.

Section 153-18B requires that "The dwelling must have adequate on-site parking spaces per dwelling unit" and that those spaces be paved with asphalt, concrete or another approved permanent material, though the Accessory Apartment Review Board may waive the requirement where it is not feasible and the Commissioner of Planning and Development recommends it. The zoning schedule supplies the number: section 213-286A requires two off-street spaces for each dwelling unit in one-family and two-family dwellings, dropping to one space per unit where the lot is under 5,000 square feet. The Town's own Accessory Apartment Review Board page states the practical test as "Provide sufficient off street parking for four cars," which is two units times two spaces. Front-yard parking is constrained separately: in the A Residence district no part of the required front yard other than a driveway or garage may be used for parking, no more than 40% of the required front yard may be driveway or parking, and there may be only one curb cut (section 213-65B through D).

This is a discretionary special permit, not an over-the-counter approval. Section 153-14 vests the nine-member Accessory Apartment Review Board with the power to "make a final determination as to whether the applicant should be granted any such permit" after finding that the use will not impair neighboring properties and will be in harmony with the article, and it may attach conditions. Section 153-16A requires a public hearing on every new application, with newspaper notice at least five days out, and section 153-17 requires the applicant to post 30-inch by 40-inch blue-on-white signs on the property for at least 10 days beforehand. Renewals skip the hearing if there have been no code violations or neighbor complaints during the permit term (section 153-16B). Building Division review, a floor plan, a survey and an inspection (or a licensed engineer's or architect's certification) come on top, and the only appeal from the Board is an Article 78 proceeding in State Supreme Court (section 153-26).

Renting the accessory apartment long term is the whole point of the permit, but the permission is temporary and personal. Section 153-15A lets the Board grant the special permit for a minimum of two and a maximum of three years, with renewal applications due at least 90 days before expiration, and the Board may refuse renewal where the applicant has code violations. The permit dies when owner occupancy ends (section 153-15B) and may be revoked for nuisance conditions, repeated police calls or any code violation on the premises (section 153-15F). No owner may hold accessory apartment permits on two Babylon properties: section 153-18A bars a permit where the same individual is an owner or co-owner of any other Babylon dwelling that already has one. The apartment cannot be sold off separately; it is an additional unit inside a one-family dwelling, not a separate lot or condominium. Babylon has no short-term-rental chapter, but section 153-2C makes it unlawful "to list, show or otherwise offer for lease, rent or occupancy any dwelling unit for which a current rental permit has not been issued," and Chapter 161 (L.L. No. 17-2023) bans "party houses," meaning dwelling units used for paid commercial events. Section 153-29 also offers a lighter alternative, a Home Share Program permit costing $5 that lets a homeowner aged 60 or older rent a spare bedroom to an employed adult or student through Homeshare LI.