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Illegal Building Conversion or Occupancy

18-09-2025
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  • A hazardous or dangerous condition
  • Illegal activity in progress

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You can report the illegal conversion, alteration, or use of a building.

Illegal Conversion or Alteration

Illegal conversion is when an existing residential or commercial building is altered or modified to create an additional room, space, or unit without first getting approval from the New York City Department of Buildings.

Illegal Use or Occupancy

Illegal use is when a residential or commercial property is being used for anything other than its regulated Certificate of Occupancy or zoning.

This can include illegally renting permanent housing to guests who stay less than 30 days. To report a residential rental less than 30 days, go to the Housing Used for Short-Term Rental (Vacation Rentals or Illegal Home-Sharing) page.

Learn if an apartment or room is illegal or unsafe.

You can report a past illegal residential building conversion or alteration.

Illegal conversions include: 

  • Making illegal apartments by altering a basement, cellar, or attic.
  • Subdividing other areas of an apartment, house, or a building illegally.

Include in your report:

  • Details about the original use of the building
  • Details about the new use of the building

To report construction without a permit or against approved plans, go to the Building Construction Complaint page.

You can report past illegal conversion or alteration of a commercial space. This includes commercial space altered for residential or manufacturing purposes.

Include in your report:

  • Details about the original use of the building
  • Details about the new use of the building

To report construction without a permit or against approved plans, go to the Building Construction Complaint page.

You can report a manufacturing building altered for other purposes, such as residential or commercial use.

Include in your report:

  • Details about the original use of the building
  • Details about the new use of the building

To report construction without a permit or against approved plans, go to the Building Construction Complaint page.

You can report a residential space used as a business. This type of activity violates zoning regulations.

Include in your report:

  • The type of business

You can report people living in commercial space. This type of activity violates zoning regulations.

You can report a rooming house, boarding house, or other Single Room Occupancy (SRO) dwelling that is used as a business, illegally converted, or overcrowded.

SRO dwellings are specific types of dwellings that rent out single rooms. Boarding houses and rooming houses are SROs. Hotels are not SROs.

An SRO unit is one or two rooms and either lacks a complete kitchen and/or bathroom or shares them with other units. They are often furnished and rent is usually paid weekly or monthly.

Any alterations to an SRO must follow Single Room Occupancy regulations.

Include in your report:

  • If work was done

To report a Single Room Occupancy (SRO) being rented as a hotel room, use the Housing Used for Short-Term Rental (Vacation Rentals or Illegal Home-Sharing) page.

18-09-2025
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