Brookhaven, NY Accessory Structures: ADU Rental Restrictions (2026)
Key Facts
- Minimum size
- 300 square feet habitable area
- Standard maximum size
- 650 square feet, 40% of home
- Discretionary maximum
- Up to 850 square feet, Inspector approval
- Bedrooms allowed
- One bedroom per accessory apartment
- Units per lot
- One accessory apartment per lot
- Transient rentals
- Barred under Town Code § 82-10
Summary
Brookhaven caps every accessory apartment at 650 square feet by right, one apartment per lot, and one bedroom, so owners can't turn a single-family lot into a rental compound. The license tied to the unit ends the moment the owner sells or moves out, and the Town won't register the unit for transient or short-term rental.
The minimum habitable area for an accessory apartment shall be 300 square feet and a maximum of 650 square feet; in no case shall it exceed 40% of the habitable area of the dwelling building in which it is located, except in certain compelling circumstances a maximum of 850 square feet may be approved, at the discretion of the Chief Building Inspector, in accordance with Table 1 below. In no event may there be more than one bedroom per accessory apartment. ... Number of accessory apartments per lot. There shall be no more than one accessory apartment permitted per lot.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: rev 4966897; v79 updated 2026-05-28; through 05-28-2026).
Full Breakdown
B(4) fixes accessory apartment size at a minimum habitable area of 300 square feet and a maximum of 650 square feet, capped at 40% of the principal dwelling's habitable area; the Chief Building Inspector may approve up to 850 square feet only in "certain compelling circumstances," using the chapter's Table 1, which drops the allowed percentage to 35% for units of 651 to 750 square feet and 30% for units of 751 to 850 square feet. B(5) limits every lot to a single accessory apartment regardless of lot size.
B(11) requires the owner to file an acknowledged statement that the provisional accessory apartment license terminates on the owner's death, on transfer of title, or the moment the owner no longer occupies the premises as a principal residence. A(2) (Chapter 82, Neighborhood Preservation), the Town will not issue a rental registration to a transient residential occupancy, defined at § 82-2 as renting for less than 28 nights, so an accessory apartment cannot be marketed as a nightly or short-term rental. B(1).
Violations & Fines
A violation of the size cap, one-per-lot limit, or license terms in § 85-258 is punishable under § 85-158.E: $2,500 to $6,000 or up to 15 days for a first offense, $5,000 to $10,000 or up to six months for a second offense within five years, and $7,500 to $15,000 with up to six months for a third offense; each week of noncompliance counts as a separate violation, and the Chief Building Inspector may revoke the license after a hearing on notice.
Frequently Asked Questions
How big can a Brookhaven accessory apartment be?
Can I have two accessory apartments on one Brookhaven lot?
Can a Brookhaven accessory apartment be rented out as a short-term or nightly rental?
Sources & Official References
Other rules in Brookhaven
New York rules heatmap·Compare Brookhaven to another location·View the New York accessory structures overview
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How other cities in Suffolk County handle adu rental restrictions.