R4 Zoning NYC Building Case Study

by | Last updated Jun 2, 2020 | NYC Zoning

What does R4 Zoning Mean? R4 is a low density Residential Zoning District in NYC. In an R4 Zoning District you can build detached or attached homes as well as small multifamily buildings.

The following is a case study of one of our projects. This was a small residential development in an NYC R4 Zoning district. This case study is of a small residential building for multifamily use and ten attached two family houses.


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, but not commercial use (unless there is a commercial overlay). You can also develop certain community facility uses, 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 in R4 are attached 1 and 2 family row houses. Row Houses are attached to each other and sometimes 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. We have another post if you want to read more about detached vs attached or semi detached.

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 Residential Development Background

Our client owns two adjacent properties on this site. These properties are touching and therefore can be combined. The original owner divided one of the two properties into 10 lots and built 10 two family houses on them. The previous owner went out of business with the houses 60% complete. Subsequently 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 quality was low and the filing with DOB was a mess. Therefore the owner fired everyone involved in the original development and brought in a new team. We were part of the new team.

Our firm came in and helped finish the project, but it was not easy. 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, but we needed a game plan. The client wanted to build attached houses. This did not seem to make sense on the property for maximizing the allowable residential units. Therefore we proposed to design 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 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 if you want to learn more.

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”. 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 one 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

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

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?

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

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.

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.


R4 Zoning Codes

As an architect I spend a lot of time dealing with Zoning and Building coeds, but these are involved and complicated issues. In this article we reviewed some of the basic concepts with regards to R4 Zoning. This post does not assume to cover every possible issue or condition, but provide a general overview of the topic.


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 us directly.


Contact Fontan Architecture


Jorge Fontan
Jorge Fontan

This post was written by Jorge Fontan AIA a Registered Architect and owner of New York City architecture firm Fontan Architecture. Jorge Fontan has earned 3 degrees in the study of architecture including two degrees from the City University of New York and a Masters Degree in Advanced Architectural Design from Columbia University. Jorge has a background in construction and has been practicing architecture for 20 years where he has designed renovations and new developments of various building types.