Preconsidered Int. No.

By Council Member Sanchez (by request of the Mayor)

A Local Law to amend the administrative code of the city of New York, in relation to construction of ancillary dwelling units

Be it enacted by the Council as follows:

Section 1. Chapter 8 of title 24 of the administrative code of the city of New York is amended by adding a new section 24-809  to read as follows:

§ 24-809 Flood risk areas. a. Definitions. For the purposes of this section the following terms have the following meanings:

10-year rainfall flood risk area. The term “10-year rainfall flood risk area” means an area designated on a map of the department of environmental protection that represents locations in the city where there is a 10 percent chance or greater of rainfall induced flooding in any year, incorporating the impacts of the projected 2050 sea level rise on sewer outfalls and storm drains as projected by the New York city panel on climate change.

100-year rainfall flood risk area. The term “100-year rainfall flood risk area” means an area designated on a map of the department of environmental protection that represents locations in the city where there is a 1 percent chance or greater of rainfall induced flooding in any year, incorporating the impacts of the projected 2080 sea level rise on sewer outfalls and storm drains as projected by the New York city panel on climate change.

Coastal flood risk area. The term “coastal flood risk area” means an area designated on a map of the department of environmental protection that represents locations in the city where there is a 1 percent chance or greater of flooding in 2080 based on New York city panel on climate change projections.

Rainfall flood risk areas. The term “rainfall flood risk areas” means the areas indicated by the 10-year rainfall flood risk area and the 100-year rainfall food risk area.

b. Rainfall flood risk areas and coastal flood risk area. 1. Interim rainfall flood risk areas. No later than 120 days after the effective date of the local law that added this section, the department of environmental protection, in consultation with the department of buildings, the office of long-term planning and sustainability, and other relevant agencies shall promulgate a rule to adopt an interim rainfall flood risk areas and post a map of such areas on the city’s website.

2. Updated rainfall flood risk areas. No later than January 1, 2028, the department of environmental protection, in consultation with the department of buildings, the office of long-term planning and sustainability, and other relevant agencies shall by rule adopt  rainfall flood risk areas to update and replace the interim rainfall flood risk areas established pursuant to paragraph 1 of this section. The rainfall flood risk areas adopted pursuant to this paragraph shall indicate a base flood level showing the projected elevation of flooding within such rainfall flood risk Areas. The department of environmental protection may update such rainfall flood risk area as it deems appropriate to reflect flooding risk based on available data. The department of environmental protection shall post and keep updated a map of such areas on the city’s website.

3. Interim coastal flood risk area. No later than 120 days after the effective date of the local law that added this section the department of environmental protection, in consultation with the department of buildings, the office of long-term planning and sustainability, and other relevant agencies shall promulgate a rule to adopt an interim coastal flood risk area and post a map of such area on the city’s website. Such map shall:

(a) Utilize federal emergency management agency coastal flood mapping data to define the current 100-year floodplain, and;

(b) Utilize the 90th percentile projection for sea level rise in New York City as determined by the New York  city panel on climate change to incorporate future flood extent.

4. Updated coastal flood risk area. Within one year of the issuance of new effective flood insurance rate maps for the city of New York by the federal emergency management agency, the department of environmental protection shall by rule adopt a coastal flood risk area to update and replace the interim coastal flood risk area established pursuant to paragraph 3 of this section. The department of environmental protection may update the coastal flood risk area adopted pursuant to this paragraph  as it deems appropriate to reflect flooding risk based on available data. The department of environmental protection shall post and keep updated a map of such areas on the city’s website.

§ 2. The definition of “FLOOD RISK AREA” in section BC 202 of the New York city building code, as added by local law number 126 for the year 2021, is amended to read as follows:

FLOOD HAZARD AREA. The following [two] three areas:

1. The area within a flood plain subject to a 1-percent or greater chance of flooding in any year. Also defined as the "special flood hazard area".

2. Where buildings are classified as Flood Design Class 4, the area within a flood plain delineated as shaded X-Zones.

3. Where an ancillary dwelling unit is constructed in a basement or cellar pursuant to Section U202, the rainfall flood risk areas and coastal flood risk areas adopted pursuant to section 24-809 of the administrative code.

§ 3. The New York city building code is amended by adding a new appendix U to read as follows:

APPENDIX U
ANCILLARY DWELLING UNITS

SECTION BC U101
GENERAL

U101.1 Scope. Except as modified by the express provisions of this appendix, in a one- or two-family dwelling, an ancillary dwelling unit shall be constructed in accordance with the requirements of this code applicable to a dwelling unit.

U101.1.1 Multiple dwelling law. Where the ADU is located within the same building as the primary dwelling, and the total number of dwelling units of such building exceeds two, the entire building shall be classified as Group R-2 occupancy and comply with all applicable requirements of Group R-2 occupancy in this code and the New York State Multiple Dwelling Law as applicable, except for basement and cellar units in the program area pursuant to U202.12. Buildings constructed as Type VA or VB construction may not be converted or altered to a three-family dwelling, such limitation shall not apply to eligible conversions made habitable pursuant to U202.12.

U101.2 General conditions. Any ADU permitted pursuant to this appendix must comply with the following conditions:

1. An ADU shall only be permitted to be associated with a primary dwelling that is classified in occupancy Group R-3.

2. An ADU shall not be used as a care facility providing custodial care to any persons pursuant to Section 310.5.

3. An ADU shall not be constructed in the rear yard, as such term is defined by the New York City Zoning Resolution, of an attached one- or two-family dwelling.

4. An ADU in a cellar must have a clear ceiling height that is at least 2 feet above the grade plane.

U101.3 Types of ADUs. Where permitted by the New York City Zoning Resolution, no more than one ADU may be constructed on each tax lot, in one of the following locations:

1. Above the grade plane, adjoining or within the same building as the one-family dwelling, including attic or enlargement, constructed in accordance with Section U201.

2. In the basement or cellar of the building containing the primary dwelling, constructed in accordance with Section U202.

3. Separated by a fire wall from the two-family dwelling, constructed in accordance with Section U203.

4. Detached from the primary dwelling, constructed in accordance with Section U204.

U101.4 Certificate of Occupancy. No ADU shall be occupied for dwelling purposes without a certificate of occupancy issued by the commissioner to permit such ADU in accordance with Section 28-118.3 of the Administrative Code. An ADU constructed in accordance with Section U203, or U204 shall require a separate certificate of occupancy from the primary dwelling unit. An ADU constructed in accordance with Section U201 and U202 shall require a new or amended certificate of occupancy for all the primary dwelling units and the ADU. In addition to Section 28-118.6 of the Administrative Code, such certificate of occupancy shall indicate the following as applicable:

1. An ADU located in the basement or cellar shall be identified as “ADU Apartment U per BC U202”.

2. An ADU located in the basement or cellar in the program area shall be identified as “ADU Apartment U per BC U202 and MDL Art 7-D”.

3. An ADU with the main entrance opening to the rear yard shall be identified as “ADU Apartment R”.

4. All ADUs shall have “Ancillary Dwelling Units per ZR 12-10 and BC Appendix U” in the comment.

5. An ADU located in the basement or cellar shall be indicated the applicable flood area designation where the premises are located, in accordance with Section U202.3.1.

Exception:  Notwithstanding Section 28-118.3 of the Administrative Code, where an authorization for temporary residence is issued by the department in accordance with a local law for the year 2024, amending the administrative in relation to a pilot program to convert existing basement or cellar apartments to habitable dwelling units and Section U202.12, a basement or cellar ADU shall be permitted to be occupied for dwelling purposes without the certificate of occupancy.

SECTION BC U102
DEFINITIONS

U102.1 Definitions. The following words and terms shall, for the purposes of this appendix, have the meanings shown herein:

ANCILLARY DWELLING UNIT (ADU).  Where permitted by New York City Zoning Resolution, the dwelling unit additional to a one- or two- family dwelling, providing permanent provisions for both sanitation and kitchen facilities, occupied or arranged to be occupied by not more than one family maintaining a common household.

PRIMARY DWELLING. The one- or two- family dwelling to which that the ADU is ancillary.

SECTION BC U103
GENERAL REQUIREMENTS

U103.1 Scope. All ADUs shall comply with this section and the applicable requirements in Sections U201 through U204.

U103.2 Light and ventilation of the primary dwelling. The creation of an ADU shall not diminish the light or ventilation of any habitable rooms of the primary dwelling in any way not in compliance with Chapter 12.

U103.3 Light and ventilation of ADU. All habitable rooms within an ADU shall be provided with natural ventilation in accordance with Section 1203.5 and natural light in accordance with Section 1205.2.

U103.4 Separate entrance required. An ADU shall be provided with a separate entrance from that serving the dwelling units of the primary dwelling, either from the exterior of the primary dwelling or directly from a public corridor within the primary dwelling.

U103.5 Separate utility required. An ADU shall be provided with separate heating, ventilation and air-conditioning system, electrical system, and gas piping  from the primary dwelling in accordance with Section U103.5.1 through U103.5.3, and separate water service or separate, accessible main shutoff valves in accordance with U103.5.4.

U103.5.1 Heating, ventilation and air-conditioning systems. A primary dwelling and an ADU shall be provided with:

1. Separate heating systems.

2. Separate ducting for heating and cooling systems. Return air openings for heating, ventilation and air-conditioning shall not be taken from another dwelling unit.

3. Separate climate controls.

U103.5.2 Electrical systems. A primary dwelling and an ADU shall be provided with:

1. Ready access to the service disconnecting means serving the dwelling unit.

2. Ready access for each occupant to all overcurrent devices protecting the conductors supplying each dwelling unit .

3. Separate sub-meters or separate meters.

U103.5.3 Gas piping. Where an ADU is served by gas piping, such piping shall be provided with:

1. Ready access for each occupant to shutoff valves serving the dwelling unit in which they reside.

2. Ready access for each occupant to appliance shutoff valves serving appliances in the dwelling unit in which they reside.

3. Separate sub-meter.

U103.5.4 Water service. A primary dwelling and an ADU may share a common potable water system, provided that there are separate, accessible main shutoff valves allowing the water to be turned off for each unit without affecting any other unit.

U103.5.5 Plastic piping. Notwithstanding any inconsistent provisions of the New York City Plumbing Code, plastic piping shall be permitted in ADUs as permitted by the New York State Residential Code.

U103.6 Fire protection system. ADUs shall be provided with fire protection system in accordance with Chapter 9 unless otherwise prescribed in Section U103.6.1 through U103.6.3.

U103.6.1 Automatic sprinkler system. Where the ADU is permitted to be classified as an R-3 occupancy by this code, the exception in Section 903.2.8 shall not apply, such ADUs shall be provided with automatic sprinkler system throughout the ADU in accordance with NFPA 13D as modified by Appendix Q.

U103.6.1.1 Sprinkler of basement or cellar ADU. Where permitted by Section U202.12, notwithstanding Section 901.9.2, the primary dwelling shall not be required to be sprinklered as a Group R-2 occupancy where the basement or cellar ADU is sprinklered in accordance with NFPA 13D as modified by Appendix Q and the building is provided with fire department access in accordance with Section 501.4.3.1 of the New York Fire Code.

U103.6.2 Smoke alarm. All ADUs shall be provided with smoke alarms in accordance with Section 907.

U103.6.3 Carbon monoxide alarm. All ADUs shall be provided with carbon monoxide alarms in accordance with Section 915.

U103.6.4 Gas alarm. Where gas service is provided in an ADU, gas alarms shall be required in accordance with Section 918

U103.7 Emergency escape and rescue openings. All habitable rooms of an ADU shall be provided with emergency escape and rescue openings in accordance with Section 1025 of the New York City Fire Code and Section 1030.

U103.8 Fire department access. For the purpose of Section 501.3.1, an ADU shall be considered as an accessory building.  Notwithstanding any inconsistent provisions of Section 501.3.2, where the main entrance to the ADU is set back no more than 100 feet from the curb line, a fire department access path shall be provided in accordance Table U103.8. Protruding objects, projections or overhangs shall not reduce such minimum clear width. Such access path shall open to the sky and unobstructed between the street and such ADU.

TABLE U103.8

MINIMUM CLEAR WIDTH OF FIRE DEPARTMENT ACCESS PATH AND MAXIMUM NUMBER OF STORIES OF AN ADU

a. “Attached” shall refer to ADUs constructed in accordance with Section U203. “Detached” shall refer to ADUs constructed in accordance with Section U204.

b. The construction class of an attached ADU shall not be lower than the primary dwelling in accordance with U203.3.1.

c. “SP” shall refer to ADUs sprinklered in accordance with Section U103.6.1.

U103.9 Sustainable roofing zones. An ADU with a roof constructed pursuant to sections U202.3 or U202.4 shall be exempt from the requirements for a sustainable roofing zone pursuant to section 1512 for any roof construction attributed to such ADU.

SECTION BC U201
ABOVE GRADE ADU WITHIN A ONE-FAMILY PRIMARY DWELLING

U201.1 Scope. An ADU located entirely above the grade plane and adjoining or within the same building of the one-family dwelling shall be constructed in accordance with Section U103 and Sections U201.2 through U201.4.

U201.2 Occupancy classification. Where the ADU is adjoining or within the same building as a one-family dwelling, both the ADU and the primary dwelling unit shall be classified as Group R-3 occupancy and comply with all applicable requirements of Group R-3 occupancy in this code.

U201.3 Fire separation. The ADU shall be separated from the primary dwelling by a fire barrier having at least a one-hour fire-resistance rating meeting the requirements of Section 420.

U201.4 Exit stairway.  The exit stair required by Section 1006.3.2 may be constructed as an interior or exterior stair serving a Group R-3 occupancy in accordance with Chapter 10. Where an interior stair is provided, such interior stair shall be enclosed in accordance with Section 1023. Where an exterior stair is provided, such exterior stair shall be permitted to be constructed of combustible materials where all of the following conditions are met:

1. The stair is at least 10 feet away from any lot line or wall of other building  on the same tax lot;

2. Sprinklers are provided throughout the in accordance with Section U103.6.1;

3. The building is lawfully constructed as Type VA or VB construction; and

4. The stair shall be constructed in accordance with Section 1011.7.2.

SECTION BC U202
ADU IN A BASEMENT OR CELLAR

U202.1 Scope. An ADU located in a basement or cellar of an existing one- or two-family dwelling shall be constructed in accordance with Section U103 and Sections U202.2 through U202.12, as required by this section.

U202.2 Definitions. The following words and terms shall, for the purposes of this section, have the meanings shown herein:

10-YEAR RAINFALL FLOOD RISK AREA: Shall have the same definition as such term is defined in Section 24-809 of the Administrative Code.

100-YEAR RAINFALL FLOOD RISK AREA: Shall have the same definition as such term is defined in Section 24-809 of the Administrative Code.

COASTAL FLOOD RISK AREA: Shall have the same definition as such term is defined in Section 24-809 of the Administrative Code.

COMMUNITY DISTRICT.  A community district established pursuant to chapter 69 of the New York city charter.

ELIGIBLE BASEMENT OR CELLAR RESIDENCE. A basement or cellar in an existing dwelling within the program area, unlawfully arranged to be occupied as an apartment and with kitchen and sanitation facilities acceptable to the department, and which apartment was in existence prior to April 20, 2024.

PROGRAM AREA. As permitted by Section 289 of the New York State Multiple Dwelling Law, Bronx community district 9; Bronx community district 10; Bronx community district 11; Bronx community district 12; Brooklyn community district 4; Brooklyn community district 10; Brooklyn community district 11; Brooklyn community district 17; Manhattan community district 2; Manhattan community district 3; Manhattan community district 9; Manhattan community district 10; Manhattan community district 11; Manhattan community district 12; and Queens community district 2 and such other community districts as may be authorized pursuant to section 289 of the multiple dwelling law.

U202.3 Prohibited locations. An ADU shall not be permitted in  a basement or cellar of a building in the following locations:

1. Within the special flood hazard area in accordance with Appendix G.

2. Within the 10-year rainfall flood risk area.

3. In Within the coastal flood risk area.

4. Within the 100-year rainfall flood risk area.

Exceptions:

1. A basement or cellar ADU shall be permitted for an eligible basement or cellar residence in the 100-year rainfall flood risk area in accordance with Section U202.12.

2. Construction of a basement or cellar ADU in the 100-year rainfall flood risk area shall only be permitted in accordance with rule of the department.

U202.3.1 Identification of flood hazard areas. Where an ADU is permitted in accordance with Section U202.3, the construction documents for the ADU shall include a statement to certify that the premises is:

1. Not located in any one of the following flood hazard areas:

1.1 Special flood hazard area, in accordance with Section G201

i. Coastal A-zone.

ii. Coastal high-hazard area.

iii. A-zone.

1.2 10-year rainfall flood risk area.

1.3 Coastal flood risk area.

2. Located or not located in the 100-year rainfall risk area.

Each such statement shall be accompanied with the applicable flood area map.

U202.3.2 Variances. The board of standards and appeals shall hear and decide requests for variances from the requirements of Section U202.3 where a building is located in 10-year or 100-year rainfall flood risk areas or the coastal flood risk area, but is not located in a special flood hazard area in accordance with Appendix G. In reviewing an application for a variance, the board of standards and appeals shall consider the conditions described in Section G105.6, and shall issue such a variance in accordance with section G105.7.

U202.4 Applicability. Where permitted by this code, a basement or cellar ADU may be permitted if one of the following conditions is met:

1. In the program area, eligible basement or cellar residences may be made habitable in accordance with a local law for the year 2024, amending the administrative in relation to a pilot program to convert existing basement or cellar apartments to habitable dwelling units and Section U202.12.

2. An existing basement or cellar space in a one-family dwelling may be converted to one ADU in accordance with Sections U202.5 through U202.11.

3. An existing basement or cellar space in a two-family dwelling may be converted to one ADU in accordance with all applicable requirements of the New York State Multiple Dwelling Law. Such ADU shall be classified as a Group R-2 occupancy and comply with all the requirements of Group R-2 occupancy in this code.

U202.5 Minimum ceiling height. Notwithstanding Section 1208.2, all habitable rooms in basements shall have a minimum clear ceiling height of 7 feet. The minimum clear ceiling height of all habitable rooms in a cellar shall be 7 feet and 6 inches.

Exceptions:

1. Where approved by the fire department, in accordance with the New York City Fire Code, the minimum clear ceiling height of all habitable rooms in a cellar shall be 7 feet.

2. Where the primary dwelling is a fully detached one- or two- family dwelling, and all exterior walls are at least 3 feet from any lot line, the minimum clear ceiling height of all habitable rooms in a cellar shall be 7 feet.

U202.6 Window requirements. Each habitable room shall have at least one window with 6 square feet of openable area to provide natural ventilation as required pursuant to Section 1203.5.1.2.1. The total net glazed area of all windows shall be not less than 10 percent of the floor area of the room served, or 12 square feet (1.1 m²), whichever is greater. Such area may include glazed areas in doors providing light directly into such room.

U202.6.1 Portions of windows below grade. Portions of windows below grade plane may be included in calculations of such minimum net glazed area required to provide natural light where all the following conditions are met: 

1. The window head is located not more than 6 inches below the lowest permitted projection below ceiling height; and

2. Such portions are surrounded by a window well or similar open area that: 

2.1 is at least 6 inches deeper than the bottom of the window; 

2.2 is at least 3 times as wide, in the direction perpendicular to the window, as the depth below grade plane of such window portions; 

2.3 is at least twice as wide, in the direction parallel to the window, including 6 inches wider on each side, as the depth below grade plane of such window portions; and 

2.4 is provided with a drain to prevent any ponding of storm water, in accordance with Chapter 11 of the New York City Plumbing Code.

3. No cantilever, permanent shading structure, or other obstruction, is less than 3 feet above the window head or protrudes more than 1 foot in the direction perpendicular to the window; and

4. No other encroachment or obstruction is within the window well, except as otherwise required by this code. Supplemental steps that provide access to the required yard, court, open space or street may also be permitted. Where provided, such steps shall be dimensioned in accordance with Section 1011.5 and shall include a landing at the bottom of such window well in accordance with Section 1011.6.

U202.7 Fire separation. An ADU in a basement or cellar shall be constructed with the following fire separations:

1. Boilers and furnaces. Any boiler or furnace in such ADU must be enclosed and separated from all habitable spaces by a noncombustible fire barrier having at least a one-hour fire-resistance rating in accordance with Section 707, provided that any opening in such fire barrier shall protected with a self-closing door.

2. Stairway enclosure. Any stairway connecting more than one dwelling unit shall be provided with an enclosure in accordance with Section 713. Where the stairway is fully contained within the ADU and such ADU is fully sprinklered in accordance with Section U103.6.1, such stairway shall be permitted to be unenclosed.

3. Existing above grade unit. The ADU must be separated from all other dwelling units by noncombustible construction having at least a one-hour fire-resistance rating meeting the requirements of Section 420.

U202.8 Means of egress. An ADU in a basement or cellar shall be provided with means of egress in accordance with this section.

U202.8.1 Emergency escape and rescue openings.  All sleeping rooms shall be provided with at least one emergency escape and rescue opening in accordance with Section 1030.

U202.8.2 Means of egress from a basement ADU. An ADU in a basement shall be provided with at least one means of egress directly to the outdoors in accordance with Chapter 10, including access to a public way. The exterior door shall swing inward and be provided with landings on both the interior and exterior sides in accordance with Section 1010.1.6, excepted as provided in Section U202.8.4.

U202.8.3 Means of egress from a cellar ADU. A ADU in a cellar shall be provided with one means of egress in accordance with Section U202.8.1, and a second means of egress to the outdoors in accordance with Chapter 10, including access to the public way, even if compliance with such standards is not otherwise required by Chapter 10 or any other law. In addition, the following shall be provided:

1. The means of egress provided in accordance with Chapter 10 shall be provided with landings on both the interior and exterior sides of the door in accordance with Section 1010.1.6, excepted as provided in Section U202.8.4.

2. Such cellar shall be considered as a story above a grade plane for the purpose of complying with Chapter 9 and Chapter 10.

202.8.4 Landing exception. An exterior landing shall not be required where the landing or floor on the exterior side is no more than 7.75  inches below the top of threshold of the exit door, and the door does not swing over the landing or floor.

U202.9 Radon levels. No certificate of occupancy or temporary certificate of occupancy may be issued for an ADU located in a basement or cellar unless a certification is submitted to the commissioner that the level of radon in such ADU after the completion of construction is tested in accordance with, and meets the standards set forth in rules promulgated by the Department of Health and Mental Hygiene.

U202.10 Vapor levels. No certificate of occupancy or temporary certificate of occupancy shall be issued for an ADU located in a basement or cellar unless a qualified environmental professional submits a certification to the department that the vapor level, after the completion of construction, is in accordance with applicable law].

U202.11 Basic stormwater prevention requirements. An ADU located in a basement or cellar shall comply with the following:

1. Water sensor and alarm. Every habitable room shall be provided with at least one water sensor with backup battery power to warn the occupants in the event of a flood. The department may promulgate rules to supplement the requirement of such water sensors and alarms.

2. Emergency preparedness information. The owner shall post all required signage in a manner proscribed by the housing maintenance code and the rules of the department of housing preservation and development and shall notify any tenants about enrollment in an emergency alert system operated by the Office of Emergency Management in accordance with rules established by the department of housing preservation and development.

U202.12 Special requirements for certain basement or cellar ADUs. An inhabited eligible basement or cellar residence and an eligible basement or cellar residence in the program area shall comply with Article 7-D of the New York State Multiple Dwelling Law, a local law for the year 2024, amending the administrative in relation to a pilot program to convert existing basement or cellar apartments to habitable dwelling units, Sections U202.12.1 and U202.12.2, and rules of the department.

U202.12.1 Authorization for temporary residence. An authorization for temporary residence pursuant to a local law for the year 2024, amending the administrative in relation to a pilot program to convert existing basement or cellar apartments to habitable dwelling units shall not be issued by the commissioner unless it is shown that the ADU located in the basement or cellar provides for the following:

1. At least one means of egress in accordance with Section U202.8.1;

2. A minimum clear ceiling height in accordance with Section U202.5; and

3. Documentation of successful inspection that such ADU does not pose an immediate risk to the life or safety of any inhabitants, furnished by the department.

U202.12.2 Phased mitigation. An ADU that has been issued a authorization for temporary residence shall meet the following requirements in accordance with a local law for the year 2024, amending the administrative in relation to a pilot program to convert existing basement or cellar apartments to habitable dwelling units:

1. No later than three months after the authorization for temporary residence is issued:

1.1 A smoke and carbon monoxide alarm in accordance with Section U103.6.2 and U103.6.3.

1.2 Emergency preparedness notification in accordance with Section U202.11.

1.3 Water sensor and alarm in accordance with Section U202.11.

2. No later than one year after the authorization for temporary residence is issued:

2.1. Fire separation in accordance with Section U202.7.

2.2. Automatic sprinkler system in accordance with Section U103.6.1.

2.3. A certification from the Department of Health and Mental Hygiene in accordance with Section U202.9 and a qualified environmental professional [ in accordance with Section U202.10.

3. No later than ten years after the authorization for temporary residence is issued:

3.1 The requirements of Section U103 and Sections U202.5 through U202.11.

3.2. A temporary certificate of occupancy or final certificate of occupancy in accordance with this code.

SECTION BC U203
ADU SEPARATED BY A FIRE WALL FROM A TWO-FAMILY PRIMARY DWELLING

U203.1 Scope. An ADU separated from the primary two-family dwelling by a fire wall that is constructed of concrete or masonry in accordance with Section 706, shall be constructed in accordance with all applicable requirements of a Group R-3 occupancy of this code, except as provided by in Section U103 and Sections U203.2 through U203.7.

U203.1.1 Occupancy classification. Where the ADU is separated from the primary two-family dwelling by a fire wall that, both the ADU and the primary dwelling unit shall be classified as Group R-3 occupancy and comply with all applicable requirements of Group R-3 occupancy in this code.

U203.2 Subgrade space limitation. The ADU shall be located above the grade plane. The finished ground level of an under-floor space below the story above the grade plane shall be level with or higher than the outside finished ground level on at least one side.

U203.3 Separate building required. The ADU shall be constructed as a separate building from the primary dwelling. Both the ADU and the primary dwelling shall provide:

1. All vertical circulation and exit systems required by this code without entering the other building.

2. All fire protection systems required by this code without reliance on the other building. A shared water supply in accordance with Section U103.5.4 shall be permitted.

U203.3.1 Construction Class. The construction class of an attached ADU shall not be lower than the primary dwelling.

U203.4 Exterior walls. Construction, projections, openings and penetration of exterior walls of an ADU shall comply with Sections 602 and 705.

U203.5 Maximum building height. The maximum building height of the ADU shall be determined in accordance with Section U103.8.

U203.6 Type VA or VB construction in fire districts. Notwithstanding Section D105.1, an ADU completely or partially located inside the fire districts as established in Section D101.2, is permitted to be constructed as Type VA or VB in accordance with Section U103.8.

U203.7 Flood mitigation. The ADU shall be elevated to the highest level as determined below:

1. Where the premises is located within the special flood hazard Area, the lowest floor of the ADU shall be elevated to the design flood elevation in accordance with Appendix G.

2. Where the premises is located within the coastal flood Risk area defined by Section U202.2, the lowest floor of the ADU shall be elevated to a minimum of 3 feet above the highest adjacent grade to such ADU.

3. Where the premises is located within the 10-year rainfall flood risk area or 100-year flood risk area defined by Section U202.2, the lowest floor of the ADU shall be elevated to a minimum of 2 feet above the highest adjacent grade to such ADU.

The department may promulgate rules to supplement the requirement of flood mitigation applicable to an ADU in the coastal flood risk area, 10-Year rainfall flood risk area or 100-year rainfall flood risk area.

SECTION BC U204
ADU DETACHED FROM THE PRIMARY DWELLING

U204.1 Scope. An ADU detached from the primary dwelling shall be constructed in accordance with all requirements of the Group R-3 occupancy in this code, except as provided by Section U103, Sections U203.2 and U203.4 through U203.7, and Section U204.2.

U204.1.1 Occupancy classification. Where the ADU is detached from the primary dwelling, both the ADU and the primary dwelling unit shall be classified as Group R-3 occupancy and comply with all applicable requirements of Group R-3 occupancy in this code.

U204.2 Egress arrangement. The ADU shall provide all vertical circulation and exit systems required by this code without entering the primary dwelling. The construction of an ADU shall not alter the egress requirements for the primary dwelling  pursuant to Chapter 10.

§ 4. Section 503.2.4.1 of the New York City fire code, as amended by local law number 47 for the year 2022, is amended to read as follows:

503.2.4.1 Group R-3 occupancies set back 100 feet or less.  The fire apparatus access road to a Group R-3 building with any main front entrance located more than 40 feet (12192 mm) but not more than 100 feet (30 480 mm) from the street line (as measured along the route of the fire apparatus access road) may be designed and constructed in compliance with the requirements of the Building Code for driveways where:

1.   The driveway is designed and is used exclusively to provide access only to a single Group R-3 building and no more than 1 ancillary dwelling unit, and to no other buildings; and

2.   The height of the Group R-3 building or an ancillary dwelling unit does not exceed 35 feet (10 668 mm) above the grade plane (with the terms "building height" and "grade plane" having the meanings set forth in Section BC 502.1 of the Building Code); and

3.   The driveway provides access to the frontage space of each occupancy, except as otherwise provided in FC 504.1.2; and

4.   The dwelling units are equipped with interconnected smoke alarms, in accordance with Section [907.2.10] 907.2.11 of the Building Code.

§ 5. Section 504.1.2 of the New York City fire code, as amended by local law number 47 for the year 2022, is amended to read as follows:

504.1.2 Occupancies with separate entrances. When a building contains more than one occupancy or a semi-attached or detached ancillary dwelling unit, and separate entrances are provided for individual occupancies, there shall be a main front entrance for each such occupancy, and a separate frontage space shall be provided for each main front entrance, except that a second frontage space is not required for a two-family Group R-3 occupancy or a dwelling unit ancillary to a one-family or two-family Group R-3 occupancy if unobstructed access, 5 feet (1524 mm) in width, is provided to the rear yard and to the main front entrance of any dwelling unit from either side of the building that is not directly accessible from the public street, fire apparatus access road, or driveway. An open accessory parking area not less than 5 feet (1524 mm) in width shall be sufficient to constitute unobstructed access to the rear yard, regardless of the presence of parked vehicles in such parking area.

504.1.2.1 Detached ancillary dwelling units. A detached ancillary dwelling unit is not required to provide frontage space if access to the main front entrance of the detached ancillary dwelling unit is provided in accordance with the requirements for unobstructed access set forth in FC 504.1.2.

§ 6. This local law shall take effect on the same date that a local law of the city of New York for the year 2024, amending the administrative code of the city of New York, in relation to a pilot program to convert existing basement or cellar apartments to habitable dwelling units, takes effect.