R4 Zoning NYC Building Case Study

(Last Updated On: April 19, 2019)

What does R4 Zoning Mean? The following is a case study of a project we are working on for a small residential development in an NYC R4 Zoning district. This article will be updated as the project develops. What is R4 Zoning? R4 Zoning in NYC means a Residential 4 Zoning District in New York City. This case study is of a small residential building for multifamily use and attached 2 family houses.

R4 Zoning NYC

What is R4 Zoning?

R4 zoning is a residential zoning district in NYC. It allows all types of residential uses including multifamily residential, single family houses, and two family houses. Certain community facility uses are also allowed, but we will not be addressing those uses in this article. Residential R4 buildings are usually small. The maximum building height is 35 feet. The most common building types you see in R4 are attached 1 and 2 family row houses, also known as townhouses. These are houses that are attached to each other and share a wall. You can also build single or two family detached houses. A detached house is one with yards on all four sides that does not touch another house or property line. These are less common in R4 zoning.

You can also develop an R4 lot into a small multifamily apartment building. The following is a case study on building one small multifamily building in an R4 Zone.

R4 Zoning Districts

R4 Zoning NYC Development

R4 Zoning NYC Development

R4 Residential Development Background

Our client owns two adjacent properties on this site. These properties are touching and therefore can be combined. Properties can also be subdivided. The original owner divided one of the two properties into 10 lots and built 10 two family houses on them. The houses were roughly 60% finished in construction when the owner went out of business. My client purchased the properties from the original owner looking to finish the construction. He immediately discover the development was full of problems. The construction and the filing with DOB were a mess. The owner fired everyone involved in the original development and brought in a new team. Our firm came in and helped finish the project. We got everything up to code and finished. We straightened out problems with the DOB including filing post approval amendments and coordinated inspections.  Eventually we obtained final Certificates Of Occupancy on all 10 of the 2 family homes. The client now has 20 families renting there.

We were now ready to develop the second property. The client wanted to build attached houses. This did not seem to make sense on the property for maximizing the allowable residential units. We proposed to do a small multi family building, and the client agreed. As I mentioned this is not usually the most common development for R4 zoning. Attached 1 and 2 family houses are far more common, but we are going with a multifamily apartment building in this option.

R4 Zoning NYC

R4 Zoning Site plan

R4 Zoning Analysis

All developments start with a zoning analysis. The zoning analysis is an in depth look into the zoning regulations affecting the development. The zoning analysis will determine how many apartments we can develop on the site, how many square feet we can build, yard requirements, and all sorts of other details. We are going to keep it to the basics, in this post, but there is a great deal of nuance and detail involved in zoning.  That’s why clients often hire us just to do a zoning analysis before starting a project. I recommend you always get your zoning analysis done by a licensed architect. Here is a post we wrote about Zoning Analysis.

R4 Zoning Development Rights & Floor Area Ratio – FAR

The FAR is a proportion that determines how many square feet you can develop on a property. When we were brought in to complete the development of the first property we realized they had not maximized their allowable square footage. This was fine with us, because we can allocate that square footage to the new development. People usually call this “air rights” transfer. Check out an article we wrote discussing NYC Air Rights.

The more technical term for “air rights” is “development rights”. The zoning text uses development rights but either way they mean the same thing. They are the right to develop a property and the amount of square footage you can legally develop on that property “as of right”.

In our example the first property did not use all of its development rights. We were not about to let that go to waste. So how do you move development rights from one property to another? You combine the zoning lots. This is called a Zoning Lot Merger. A Zoning lot is different from a property lot (tax lot). A zoning lot is the area of property included in determining the zoning for a development. The zoning lot is conceptual. It can be made of multiple property or tax lots as long as the lots are touching. So even though the two properties are separate properties. We can conceptually join them as 1 zoning lot. But they are 2 separate real properties. In reality they are 11 properties but I am trying to keep it simple. The first property was previously divided in 10 real property lots when they did the original houses. Either way we are combining the empty property and the developed properties into 1 zoning lot.

What is R4 Zoning

R4 Zoning lot

Determining what you can build on an R4 zoning lot?

When you combine the multiple zoning lots into 1 zoning lot you start by figuring out the total allowable square footage of the new combined zoning lot. You then subtract whatever has been used by the completed development of houses. That will give you the new development rights. Are you confused? Lets do some math. I’ll try to keep it simple.

The properties combined lot area is = 28,369.28 Square feet

Therefore the new Zoning lot area is = 28,369.28 Square feet

The FAR in R4 Zoning is .75 that is the ratio to determine the buildable square footage. R4 also has what is called an attic allowance. This allows you to increase the FAR to .9 as long as the increased area is under a pitched roof with a height between 5′ and 8′. We are going to calculate the allowed zoning floor area. This is how much total square footage of floor area is allowed on the zoning lot.

Zoning Floor Area = Zoning lot area X FAR

Zoning Floor Area = 28,369.28 Square feet X .9

Zoning floor area = 25,532.82 square feet

We now have to deduct all the floor area used by the original 10 two family houses. Those all add up to 20,684.3 sq ft.

New Building Floor Area = Allowable Zoning Floor Area – Used Floor Area

New Building Floor Area = 25,532.82 sf – 20,684.3 sf

New Building Floor Area = 4,848.52 sf

So we now know we can build a small building of a maximum 4,848.53 square feet.

The maximum building height in R4 is 35 feet. We aren’t even going to go that high. We are going to do a two story building. Each floor will be about 2,424 sq ft.

How many apartments can we put in the new building?

So we already know our total building floor area. We now need to figure out how many apartments we can put. WARNING This involves more math. The number of units is determined by dividing the Allowable Zoning Floor Area of the Zoning lot by the dwelling unit factor. In R4 zoning the dwelling unit factor is 870. The factor changes between zoning districts. It is only 870 in R3-2, R4, R4-1, and R4B Zoning districts. Do not mix up Zoning Floor Area with Zoning Lot Area when doing this calculation. Here’s the math:

Number Of Dwelling Units = Zoning Floor Area / Dwelling Unit Factor

Number Of Dwelling Units = 25,532.82 sf / 870

Number Of Dwelling Units = 29

That’s 29 counting the original development. We now subtract what has been used by what is allowed. The original development was 10 two family houses. Each family is 1 dwelling unit or 1 apartment. So we are doing 10 x 2 = 20 dwelling units used.

Allowed apartments in new building = Total allowed dwelling units – used dwelling units

Allowed apartments in new building = 29 – 20

Allowed apartments in new building = 9

We can build a maximum of 9 new apartments in a 4,848.52 square foot new building. I told you it was going to be a small building. These are of course the maximums we can build less. 

All Units require parking.

R4 Zoning

R4 Zoning Site Plan

Zoning R4 Small Building Design

We are currently designing the new building. We will hopefully be posting a 3D rendering when the design is complete.

It looks like we are going to end up doing 8 apartments. 4 on each floor of the 2 story building. The client was more interested in doing 8 slightly larger apartments than 9 smaller ones.

Thank You for reading our blog post on R4 Zoning.

I hope this was helpful. If you want to discuss a specific project with an architect please feel free to Contact Fontan Architecture. We will be happy to help. Or learn more about or NYC Architecture Firm.


  • Jorge P

    March 11, 2017 5:51 am

    Great article Jorge! I have an R4 lot I’m going to be purchasing in the Bronx. Would love to get your feedback on the best way to maximize the lot.

  • Hangman

    March 15, 2017 9:03 pm

    So if I purchase a 4000 lot (40×100) detached , I can technically build 4 units @ 870? by using that .90 attic roof (4000*.9/870=4.13?) How do you solve the parking problems per unit? Thanks.

  • John Bartek

    June 28, 2017 1:06 am

    great article… i have a 100×100 in maspeth Queens I’m selling. i would be interested to hear what you think can be built there with R4-1 zoning.

  • Siddique

    August 28, 2017 7:16 am

    Hi Jorge, this is such a great article and very helpful for people who really need to get some ideas about how NYC zoning work. I have a question, but I am not sure how appreciate to ask it here. But I am SO curious to know about it. Roughly, how much it will cost to build a two families house with 2,000 square feet (1,000 square feet in each floor total 2 floor plus basement) in queens, Jamaica?
    I know it’s depend on a lot of things, but just general idea. And once we get permit, how long it will take to build it? Thanks for your help

  • Kevin Scrobola

    November 14, 2017 3:34 pm

    Hello Jorge I currently own an oversized lot zoned R4A. The lot is 50×140. I know R4A is zoned 1 and 2 family but is there potential to build something larger because of the oversized lot?
    Thank you

  • Mike Cottone

    March 1, 2018 3:34 am

    Hi Jorge,
    I own 2 adjacent lots on a corner in Ozone Park, zoned R4, front facing one street. They are each 40×100. Can the lots be divided into 4 lots with the frontage facing the other street? Would the city allow that?

  • Monica

    April 27, 2018 9:32 am

    Hi Jorge,

    Thank you for such a great article. I have a question, can I build 2 family house on R4B zoning 19.5×90 property (building size 19.5×35)? It is an attached 1 family row house in Bayside with community drive and attached garage in the back of the house. Thank you! Eve

  • Denny

    June 17, 2018 1:41 am

    Hey Jorge,

    I love your content! Very informative! There is a property located on R4-1 and R5B that I am looking at and the agent is telling me that it’s R5B zone. When I check the zoning map it seems that 8×100 of the 2200 lot is R5B. What does that mean? Can I build according to the R4-1 rules or R5B rules?

  • Mike

    June 18, 2018 7:26 pm

    Hi Jorge,
    WOW that article open my brain. I saw a detach one family house at R4 zoning, lot 20X100. Existing building 1020 sf. I know FAR (.85+.15) for R4 but I just want to know if I can convert that property to small 1or2 BR two family family without any major construction in Jamaica, Queens just with your filling to DOB by your office. Please let me know.
    Thanks a lot.

  • Shaikat Ahmed

    August 13, 2018 3:50 am

    Hi Jorge, I have a property in Ozone Park Queens. Property consist of lot Area 5,800 sqft. On left side of the property sits 3 family building and the adjacent lot is a huge drive way with a 4 car brick garage. Could you tell me based on the information that I provided what can be built on the adjacent lot with keeping the existing 3 family building ? Thanks.

    Lot Frontage 84.58 ft
    Lot Depth 100 ft
    Year Built1920
    Building Class Walk-up Apartments – Three Families (C0)
    Number of Buildings2
    Number of Floors2
    Gross Floor Area 2,704 sq ft
    Total # of Units 3
    Residential Units3

  • Thurman Bligen

    September 15, 2018 8:22 pm

    Good Evening Jorge,
    I am very unfamiliar with NYC zoning. If I purchase this property, which was a medical office building, with the following dimensions, how many stories and apartments can I build?
    Lot Dimensions: 126.09′ x 118.08′ 25.35′ x 118.15 151.35′ x 118.15′ (Irregular)
    Lot Size: 14,832 SF (approx.)
    Building Dimensions: 85′ x 85′ (Irregular)
    Stories: 3
    Commercial Units: 14
    Parking Spaces: 36
    Gross Building SF: 23,112 SF (approx.)
    Target Rentable SF*: 26,911 SF (approx.)
    Zoning: R4
    Commercial FAR: 0.90
    Facility FAR: 2.00
    Facility Buildable SF: 29,664 5,802 35,466 SF (approx.)
    Minus Existing Structure: 23,112 0 23,112 SF (approx.)
    Available Air Rights: 6,552 5,802 12,354 SF (approx.)

  • Ketty

    September 22, 2018 10:45 pm

    Sorry I’m late to the party. Im trying to buy a single family house and build an addition in the back. It’s R4, attached and has parking on the street only. I’m wondering if the parking requirements apply.
    Also, does the 30ft clearance

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