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Proposed Rule – Rules relating to Ancillary Dwelling Units in 1 and 2 Family Dwellings

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Rule status: Proposed

Agency: DOB

Comment by date: August 18, 2025

Rule Full Text
Proposed-Rule-Rules-relating-to-Ancillary-Dwelling-Units-in-1-and-2-Family-Dwellings.pdf

The New York City Zoning Resolution (ZR) was amended to define and allow ancillary dwelling units (ADU or ADUs) as part of the City of Yes Housing Opportunity text amendment, effective 12/6/2024. The ZR defines an ADU in part as "an additional dwelling unit, permitted on the same zoning lot as a single- or two-family residence that does not exceed eight hundred square feet of floor area. Only one ancillary dwelling unit shall be permitted per every single- or two-family residence on a zoning lot." The New York City Council also adopted corresponding construction requirements for ADUs in existing buildings in Local Law 127 of 2024 (LL127), effective June 16, 2025.

LL127 gives authority to the Department of Buildings (DOB) to promulgate rules in consultation with the Fire Department and Office of Emergency Management for any standards protective of life. This proposed rule provides safety features and administrative requirements necessary to implement LL127 in conjunction with the ZR for single- and two-family homes.

It should also be noted that additional safety requirements necessary to implement LL127 are being promulgated by: 1) the Department of Environmental Protection (DEP) related to establishing flood maps in the 10-year rainfall flood risk area; and 2) the Department of Health and Mental Hygiene related to testing and protection for both vapor and radon levels.

The proposed rule 105-08:

• establishes the scope of the rule to include ADUs associated with single- or two-family residences and incorporates references to both NYC Building Code Appendix U (BC Appendix U) adopted by LL127, and the definition of "ancillary dwelling unit" in ZR section 12-10,

• incorporates references to eligibility criteria from the ZR definition and BC Appendix U for constructing ADUs, including the reference to the limitations on ADUs in areas of special flood hazard as defined by the NYC Construction Codes, and the 10-year rainfall flood risk area, which will be set out in a rule promulgated separately by DEP,

• clarifies the criteria to be applied when an ADU is proposed to be included in the development of a new single- or two-family residence,

• sets administrative requirements for identifying ADU filings and includes requirements for certificates of occupancy, building identification numbers (BINs), and requirements to obtain house numbers from the requisite Borough President's office Topographical Bureau,

• establishes technical requirements for ADUs including, flood mitigation, water sensors, entrance identification, and occupancy restrictions, and

• adds requirements regarding egress, sprinklers and windows for ADUs located in cellars as part of such development."

DOB’s authority for these rules is found in sections 643 and 1043(a) of the City Charter, Appendix U of the New York City Building Code, and Local Law 127 of 2024.

Send comments by

  • Email: [email protected]
  • Mail: Department of Buildings, 280 Broadway ; New York, New York 10007

Public Hearings

Attendees who need reasonable accommodation for a disability such as a sign language translation should contact the agency by calling 1 (212) 393-2085 or emailing [email protected] by August 4, 2025

Date

August 18, 2025
11:00am - 12:00pm EDT

Connect Virtually
https://events.gcc.teams.microsoft.com/event/f8f26909-9dfe-4807-a277-0bd5844223e8@32f56fc7-5f81-4e22-a95b-15da66513bef
Phone: 646-893-7101

Phone Conference ID: 244 039 527#

Disability Accommodation
  • Communication Access Real-Time Translation

Comments are now closed.

Online comments: 14

  • Esah Ali

    I live in Old Mills Basin and have space in my very large backyard to extend my home or build an ADU. I also have a finished basement that I would like to certify as a dwelling unit. When is my neighborhood eligible? How do I start the process?

    [PERSONAL INFORMATION REMOVED BY WEBSITE ADMINISTRATOR]

    Comment added July 19, 2025 11:37am

  • Chelsea Albucher

    I am really excited about ADU policy, and hope the implementation includes programs to support 1. seniors both in terms of providing housing, and in terms of providing additional income older homeowners, 2. an emphasis on assisting people of color in maintaining / developing inter-generational wealth – e.g. financing, technical assistance, not only for ADU development but also succession planning, 3. assistance with requirement and/or options for participating in housing affordability programs for a set time-frame, not in perpetuity so that accommodation may be available for older family members, 4. work with financial community to ensure financing availability (many banks do not understand how to finance ADUs). Thank you for your work. I truly believe ADUs can help provide more housing options without significantly altering neighborhood fabric. Note this is support from a Staten Island property owner.

    Comment added July 21, 2025 10:29pm

  • RACHELE A GARGIULO

    This program is the most ridiculous program i have ever heard . Who is making these proposals. I am against ADUs.
    You people are destroying the 5 boros of this city. Certain areas are already terrible and destroyed. Remove the illegal first. Then get the drug attics and homeless off the streets. Get them the professional help they need in a facility. All the city council members constantly waste millions of our tax dollars and accomplish nothing . You never have a good plan. We the people who pay the taxes do not want homeless people, drug attics, illegals who have problems and are broke living in our community. Stop destroying our city. Wake up and save the taxpayers money. And the people who want these ADUs on their property are just looking for money from the city and state, and they dont care about the people. If you people vote for Mamdani , he will totally destroy the boros and the city. Your plan is terrible.

    Comment added July 24, 2025 9:02am

  • Nim Ginsburg

    Please see the attached PDF document containing my comments to the Proposed Rule.

    Comment attachment
    Comments-on-DOB-Proposed-Rule.pdf
    Comment added July 24, 2025 3:08pm

  • Thomas Soviero

    According to Section U202.7 – Fire Separations:
    Why is an Accessory Dwelling Unit (ADU) located in a basement required to have a minimum one-hour fire-resistance-rated separation constructed of non-combustible materials, while an apartment unit within a two-family building is allowed to meet the same one-hour rating using any code-permitted materials, including combustibles? Both ADUs and apartments serve the same function as independent dwelling units. Requiring stricter material standards for ADUs, despite their functional similarity to apartments, appears inconsistent with the intent of uniform safety provisions.

    Comment added August 5, 2025 10:38am

  • Thomas Soviero

    There is an inconsistency between the Proposed Rule 105-08(d)(4)(iii) and 105-08(d)(4)(vii)(D) and section 27-2087(a) of the Housing Maintenance Code. The Proposed Rule 105-08(d)(4)(iii) states that Occupancy of an ADU in a cellar, as defined by section 202 of the Building Code, must be in accordance with section 27-2087 of the Housing Maintenance Code. However, HMC Section 27-2087(a) states that no room in the cellar of a one or two family dwelling shall be rented and no member of the family or families occupying the dwelling shall use such room for sleeping, eating or cooking purposes. Furthermore, Proposed Rule 105-08(d)(4)(vii)(D) states that applications for ADUs in a cellar may not be submitted unless and until section 27-2087 of the Housing Maintenance Code provides for such occupancy in cellars. When will the HMC be updated? Please clarify.

    Comment added August 5, 2025 11:44am

  • Thomas Soviero

    Proposed Rule 105-08(f)(2)(i) states that water sensors and alarms must be installed in every habitable space in an ADU located in a basement or cellar to provide warning to the occupants in the event of a flood. Why would this be applicable if ADUs are prohibited from being located in a basement or cellar within the Special flood hazard area, 10-year rainfall flood risk area or Coastal flood risk area? If the ADUs are located outside of these areas, the likelihood of flooding is significantly reduced and water sensors and alarms would not be necessary.

    Comment added August 5, 2025 12:01pm

  • Gaetano Donatantonio

    There seams to be some confusion as to wether Basement and/or Cellar ADU’s are permitted in new construction of 1 and 2 family dwellings. Both Appendix U [U202.1] and this proposed new section 105-08 [(e)(1)(ii)] refer to … cellar and basement ADU’s in ‘EXISITNG’ in existing building…

    Comment added August 5, 2025 3:26pm

  • Gaetano Donatantonio

    Regarding Cellar ADU’s: Is there any insight as to when the Housing & Maintenance Code (HMC) will be amended to allow for habitable rooms in a cellar? Until the HCM is amended – I do not see any ADU’s in cellars of either existing or new construction.

    Comment added August 5, 2025 3:28pm

  • Wil Fisher, Unit Two Development LLC

    On behalf of Unit Two Development LLC, we respectfully file the attached comments. Thank you

    Comment attachment
    Unit-Two-Comments-ADUs-in-1-and-2-Family-Dwellings.pdf
    Comment added August 10, 2025 7:30pm

  • Chaya Raichik

    Hi,

    I would like to comment that

    1. The rules should include basement egress windows as a valid form of egress, in addition to a door, from a basement or celler unit.

    Nearly all other fire and egress building codes, including IBC, allow for basement egress windows, with window wells (and ladders) to be used as a means of egress.

    I am specifically referring to windows that are more than 50 percent underground and use a well or similar.

    See here: https://codes.iccsafe.org/s/IRC2015/chapter-3-building-planning/IRC2015-Pt03-Ch03-SecR310.2.3

    2. Please amend the rule to include allowing existing basements and
    Cellers to convert to ADU, not just new construction.

    Comment added August 14, 2025 2:06pm

  • Fernando Estrella

    I am NOT in favor of allowing ADUs be built. You have not provided a plan for how you will mitigate the greater demand on the city’s infrastructure. More units on a lot means more people; more cars; more traffic; more demand on water, electricity, sewage and garbage; more kids in an already crowded school system. What is your plan for addressing these challenges? Until you address these issues, the answer should be no.

    Comment added August 15, 2025 8:00pm

  • William S.

    If ADUs needs a $20,000 – $60,000 sprinkler, no ADUs will get built. If the goal is to create only 10 of the 15,000 new home goal, this will fail spectacularly, just as the pilot program in East NY because of cost due to impossible rules and gross over regulation.

    The Basement Apartment Conversion Pilot Program, launched in 2019 to legalize basement units in East New York and Cypress Hills, began with over 8,000 potential homes identified—but only about 100 homeowners reached the assessment stage. As of mid-2023, just five homes remained enrolled, and only one had begun construction—an wholesale failure by any measure.

    Another report put it even more sharply: only two of a projected 102 potential units proceeded due to sky-high costs—averaging as much as $250,000 per home—and regulatory hurdles that blocked the rest of the applicants.

    The goal of ADUs is to create safe, legal, and affordable homes. But cost due to impossible requirements and over regulation, like the sprinkler mandate, makes them financially unfeasible. Safety standards can be achieved through less costly measures—otherwise this will fail just as all the rest did.

    It’s great that there is aid for low income homes, but the middle class is forgotten. The project will fail just as it did in East NY.

    Comment added August 16, 2025 10:11am

  • vishal narine

    Im located in south ozone park. will sprinkler be required for deatched adu located in rear of the property that have a 5 ft or more fdny access path. along with if you do a garage under the adu as stated in the zoning code will you allow for the one side to be 1 foot from the property as garages are permitted to be 1 foot from the property line.

    Comment added August 18, 2025 10:26am