ADU rules in Brookhaven

Brookhaven's only ADU pathway is the accessory apartment, and it has to be inside the house. Section 85-258B(2) says flatly that an accessory apartment 'shall be located in the principal dwelling,' and the Chapter 85 definition describes it as a dwelling unit 'located within the principal structure.' A full read of Chapter 85 turned up no detached-ADU, backyard-cottage or garage-conversion provision anywhere in the code, and no defined term 'accessory dwelling unit' at all. The nearest detached accessory living space the code recognizes is a guesthouse, defined as temporary accommodation for guests 'without any cooking facilities,' which is not a dwelling unit.

An accessory apartment carved out of the principal one-family dwelling (basement, attic, wing or internal conversion) is allowed, but as a licensed accessory use with real gates rather than an as-of-right unit. Section 85-258A authorizes accessory apartments in the A Residence, A Residence 1, A Residence 2, A Residence 5, B Residence, B Residence 1 and C Residence Districts, and § 85-190B(8) lists them as an accessory use in the A Residence District (the other residence districts adopt that accessory-use list by cross reference). The conditions that most often bite: the owner must live in the same dwelling, only one accessory apartment is allowed per lot and per dwelling and per homeowner, the unit may have only one bedroom, entities such as LLCs and corporations cannot hold a license, an accessory apartment is barred in an existing multifamily structure, and no license may issue where 5% or more of the lots within a half-mile radius already have accessory apartments.

Section 85-258B(4) sets both an absolute range and a share-of-house ceiling, and Table 1 ties the two together: the standard band is 300 to 650 square feet at up to 40% of the dwelling's habitable area, while 651 to 750 square feet (35%) and 751 to 850 square feet (30%) are available only 'in certain compelling circumstances' at the Chief Building Inspector's discretion. The percentage is measured against the habitable area of the dwelling building containing the apartment, so a small house can hit the 40% ceiling well below 650 square feet. The one-bedroom cap is absolute: 'In no event may there be more than one bedroom per accessory apartment.'

Owner occupancy is required at application and continuously afterward. Section 85-258B(1) requires the owner of the lot to 'reside within the dwelling that contains the accessory apartment,' and the owner may occupy either the larger unit or the apartment; no co-owner may hold a larger share than the owner-occupant, and entities (LLCs, corporations, partnerships, professional corporations) are expressly barred from obtaining a license. Under B(11) the applicant must file an acknowledged statement that the license terminates on the owner's death, on transfer of title, or when the owner no longer occupies the premises as a principal residence. The current PAAL owner affidavit in the Town's application makes the applicant swear the property is 'my PRIMARY and ONLY RESIDENCE' and consent to periodic inspections. New York has no statewide ADU law preempting this.

Section 85-258B(8) requires a minimum of two off-street spaces for the resident-owner plus at least one on-site space designated for the apartment's occupants, shown on a plan filed with the application and reserved for those occupants only. Tandem stalls count as a single space, and the spaces and the driveway serving them must be paved with asphalt, concrete or similar material; gravel and other permeable surfaces are not accepted. Failure to keep the parking in compliance is grounds for revoking the license. The Chapter 85 Table of Parking Requirements repeats the add-on: '1 on-site off-street parking space per dwelling unit when an accessory apartment is permitted by § 85-258.'

Administrative, with a license rather than a hearing. The applicant files with the Building Division for a Provisional Accessory Apartment License plus all necessary building permits, and the Chief Building Inspector issues the license once the apartment is complete and safe to occupy; the Town's current form charges a $250 fee, requires in-person filing, and states the license is valid for 2 years. The only public-input step is a poster the applicant must post along each road frontage for 10 consecutive days once the application is deemed complete, telling neighbors they may contact the Building Division within 10 days; no Zoning Board of Appeals or Town Board hearing is required. L.L. No. 3-2024 (effective 2-27-2024) moved this process from the former Accessory Apartment Review Board to the Chief Building Inspector, and the word 'Review Board' no longer appears anywhere in Chapter 85, although the Town website still carries a Review Board directory entry and a 2019 FAQ that describe the old process.

Section 85-2D makes it 'unlawful for either an entire dwelling unit or a portion thereof, including but not limited to a residence with an accessory apartment, to be occupied by a transient residential occupancy,' and § 85-884B bars transient residential occupancy in every district. The § 85-1 definition covers a 'dwelling unit or portion therein' rented for under 28 nights to anyone other than the owner or a family member, and a rebuttable presumption treats any listing on Airbnb, HomeAway, VRBO or similar media as proof of the use. Chapter 82 runs the separate rental registration regime (a registration is valid 15 months, requires an inspection, and § 82-10A(2) forbids issuing one for a transient residential occupancy); the Town's rental license forms and fee schedule are aimed at non-owner-occupied dwellings, while an owner-occupied house with an accessory apartment is licensed under § 85-258. The apartment cannot be sold off separately: it is part of a one-family dwelling and the license is personal to the owner-occupant, although § 85-258D(3) lets a license be transferred to a new owner for the unexpired term.