Converting 1-Family to 2-Family in Brooklyn R6 Zoning

For anyone familiar with zoning and DOB approvals in NYC, how difficult is it to legally convert a one-family home into a two-family in Brooklyn on a lot that’s zoned R6? I’m looking for insight on what the main hurdles are, such as DOB approval process, potential structural requirements, certificate of occupancy changes, and whether community board input plays a role. Anyone here gone through it or know the real-world costs and time involved?

sphil305

in Real Estate - General 5 days ago

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michaelhanson | 7 hrs ago

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The Fire Code essentially tells you that, if you’re on a narrow street, converting the ‘garden level’ into a separate apartment needs to be sprinklered, but the rest of the house does not, unless the renovation causes the value to increase by 60% or more (according to DoF calculations, as jimhillra points out), of if you add more than 125% of the existing floor area. In my experience, a conversion can often be kept under the 60% trigger, so the rule of thumb is to budget for sprinklers on the garden level apt on a narrow street, and on a wider street, to design with an eye to the 60% value trigger.

jimhillra | 9 hrs ago

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The value of the building in the code below is not the real estate price. It is a result of a calculation based upon the Dept of Finance assessed value.

The fire code section pertains to houses on streets less than 34 feet curb-to-curb, which is most streets, but not most avenues.

jimhillra | 9 hrs ago

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Building code and Fire code sections follow:
NYC Building code:
901.9.4 Additional requirements based on value of alterations.
Fire protection systems shall be provided to buildings and spaces in accordance with the provisions of Sections 901.9.4.1 through 901.9.4.3.

901.9.4.1 Alterations requiring fire protection systems throughout a building.
If the value of alterations to the building equals or exceeds 60 percent of the value of the existing building, or, in the case of a building containing 4 or more dwelling units, 50 percent of the value of the existing building, the entire building shall be made to comply with the fire protection requirements of this chapter as if it were hereafter erected.

901.9.4.2 Alterations requiring fire protection systems in the space being altered.
If the value of alterations of a space is between 30 percent and 60 percent of the value of the existing building, or, in the case of a building containing 4 or more dwelling units, if the value of alterations of a space is between 30 percent and 50 percent of the value of the existing building, those portions of the building being altered shall be made to comply with the fire protection requirements of this chapter.

(901.9.4.3 does not apply here)

NYC Fire Code:
501.4.3.1
A one-family Group R-3 occupancy is being altered to a two-family Group R-3 occupancy, except where:
the alteration involves converting a basement space to a separate dwelling unit, and the new basement dwelling unit is protected throughout by a sprinkler system;

sphil305 | 1 day ago

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Could you clarify under what conditions the DOB would require the installation of sprinklers as part of this conversion?

cate | 2 days ago

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When converting from a one-family to a two-family and changing the C of O, the DOB may require you to add sprinklers to the house, and your property tax may increase to the full amount a year after the new C of O is signed off on.

michaelhanson | 3 days ago

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Converting from 1-family to 2-family is the same occupancy as far as code is concerned (R3 – 1- & 2-family homes), and zoning should not be an issue unless you’re adding to the building or converting some existing floor area into habitable space. You’ll need to file an Alt-1 with the DOB and get a new or updated Certificate of Occupancy. In all, it’s not too complicated from the perspective of the red tape & process – the cost can vary depending on how much you’re doing – keep in mind, you’ll (probably?) be adding a kitchen, and possibly a bathroom – and plumbing changes tend to cost more than moving or adding walls. That said, I’ve worked with several clients to add a rental to their home – your best bet is to find an architect to discuss the process and learn what to expect – let me know if you want to discuss, I’d be happy to talk it through with you (I’m a residential architect)