R4 Infill Housing Predominantly Built Up Area

by | Last updated Jul 10, 2020 | NYC Zoning

R4 Zoning is a residential zoning district in NYC that allows for one family and two family as well as small multifamily residential building. In certain R4 Zoning areas you may be able to apply the optional zoning codes for R4 Infill housing in Predominantly Built Up Areas. Infill Housing will give you a larger building than regular R4 zoning. You can build detached, semi detached, and attached buildings in R4 infill zoning.


R4 Predominantly Built Up area

This post will focus on regular R4 with optional Infill Housing, there are different types of R4 Zoning including subdistricts:


Predominantly Built Up Areas:

There are 2 zoning districts that qualify for Predominantly Built Up Area:



R4 Zoning is considered “low density” residential zoning. It typically has 2 or 3 story homes of 1 or 2 families each or small multi family buildings. R4 zoning most commonly has attached homes. R4 zoning is found in The Bronx, Brooklyn, Queens, and Staten Island.


Multi Family Buildings In R4 Infill

A Multi family building is any building with 3 or more residential units. Multi Family is not as common in R4 as one and two family homes, nonetheless you can develop either. We have an R4 case study of a development involving both 2 family homes and a multi family building in The Bronx.


R4 Infill Housing

Predominantly Built Up Area R4

If a property is located on a block that is completely within an R4 zoning district it may qualify for R4 Infill Housing also known as Predominantly Built Up Area. Properties qualifying as R4 “Infill Housing” have a separate set of zoning specifications where you can develop a slightly larger building.

Qualifying for R4 Infill Housing:

To qualify for R4 Predominantly Built up area the property must be on a block where the entire block is in an R4 zoning district. It does not count if part of the block is in R4-1, R4A or R4B zoning. The block in question must be at most 4 acres or 174,240 square feet. At least 50% of the lots on the property must be developed with buildings. The buildings on the block must verified to have a Certificate Of Occupancy issued 3 years or more before the application. If no C of O is found some other evidence must be provided to verify the legal status of the property.

The lot to be developed cannot be over 1.5 acres or 65,340 sq. ft.

For Empty Lots in Predominantly Built Up Areas:

For an empty lot to qualify it must only conform with the 50% or more of the properties rule. IT must have been an empty lot since before October 21st 1987.

Occupied Lots in R4 Predominantly Built Up Area:

Occupied lots qualifying for Predominantly Built Up Area may qualify if on the entire length of the street front and the street front of the block across the street have 50% or more mutifamily, attached, commercial, or manufacturing buildings. This applies to properties with single or two family detached or semi detached residences as of October 21st 1987.


R4 Infill Housing, Predominantly Built Up Area Regulations

A Detached house has yards on all sides and does not touch any other buildings or houses.

Minimum Lot width =40 Feet

Minimum Lot Area = 3,800 Sq Ft

Lot Size for Semi-Detached or attached:

Semi detached houses are built in pairs they touch in the middle but have yards on the sides. Attached houses are built to the property lines. Side yards can be waived for the abutting side(s) of attached buildings. There are requirements for this that must be met to qualify.

Minimum Lot width =18 Feet

Minimum Lot Area = 1,700 Sq Ft

Lot Coverage:

The development can cover a maximum of 55% of the property.

Floor Area Ratio (FAR):

Floor Area Ratio determines the floor area that can be built on the property.

FAR = 1.35

This is higher then the typical R4 zoning FAR.

Density Factor or Dwelling Unit Factor (DU)


Building Heights: 

Perimeter Wall Height = 25 Feet

Building Height = 35 Feet


Front Yard = 18 Feet minimum

Rear Yard = 30 Feet

Side Yards Detached = 13 Feet in total with the smaller being 5 feet each

Detached buildings with 3 or more dwelling units must have 2 side yards with 8 feet each. If the building is greater than 80 feet wide the side yards must be 10% of the building width.

Side Yards Semi Detached = 8 Feet


1 Parking Space must be provided for 66% of the dwelling units.


R4 Infill Zoning Example

Here is an example zoning analysis. Be aware that zoning is complicated and I am only addressing the basics here. I assure you there are many additional issues and variations to consider beyond this example.

R4 Infill Example Lot

Lets assume we have a 40 foot wide and 100 foot deep property in R4 Infill Housing in Brooklyn on an interior lot.


R4 Infill zoning Calculations:

Zoning Floor Area/ Floor Area Ratio (FAR)

So the floor area ratio is 1.35. The FAR is a ratio that determines how many square feet you can build on the property. You take the property size and multiply it by the FAR.

In this example we have:

FAR of 1.35

Lot Size of 40 feet x 100 feet.

Zoning Floor Area = Lot Area X FAR

Lot Area = 40 x 100

Lot Area = 4,000 sq ft

FAR = 1.35 or

Zoning Floor Area = 4,000 sq ft x 1.35

Zoning Floor Area = 5,400 sq ft

How many families can we have on our R4 Infill zoning lot.

Zoning regulates the maximum number of residential units you can put in a building.

We can build a multifamily building with 6 apartments.


R4 Infill Zoning in NYC

As an architect I study Zoning Codes closely, but these are complicated and quite involved issues. In this article we reviewed some of the basic concepts with regards to the R4 Predominantly Built Up Area. 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 Infill Housing.

I hope this was helpful. You can leave questions or comments below. If you want to discuss a specific project with an architect please feel free to contact us directly.


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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.