Density Factor is a zoning term for the maximum allowable number of residential units one can develop on a property. The allowable residential square footage of the building is divided by the density factor to determine the allowable number of units. These factors vary in different zoning districts. Density factor is also known as Dwelling Unit Factor or DU.
Density Factor Definition
The following is based on The New York City Zoning Resolution.
Density Factor is a formula for determining how many dwelling units can be placed on a lot. Therefor DU is a critical issue for a Zoning Analysis, Feasibility Study, or Pro Forma. The density factor or dwelling unit factor is based off the zoning district for that location. There are low, medium, and high density Zoning Districts in NYC. It is NYC`s way of regulating density throughout the city.
Finding Your Density Factor
In order to calculate your density factor you need to calculate your Maximum Buildable Area, which you can find information to do so in our Floor Area Ratio post. Once you have that you will have found your zoning district and below you will find your Factor For Dwelling Unit based on that.
DU Factor NYC Zoning
|District||Factor for Dwelling Units||Special Notes|
|625||R3-2 for single and two family detached and semi-detached residences only|
|900||R4 Ifill & R5 infill In Predominantly Built Up Area only.|
|R5B||1,350||for lots with less than 40 feet street frontage and existing on the date of establishing the R5B districts on the zoning map.|
|680||This goes for all R6 - R10 Districts including subdistricts and contextual zoning.|
DENISTY FACTOR CALCULATION
Maximum Buildable Area for Residential X Factor for Dwelling Units = Dwelling Units Allowed
Maximum Buildable Floor Area = 9,000 SF
Zoning District = R6
Factor for Dwelling Units = 680
Maximum Buildable Area /Factor for Dwelling Units = Number of Dwelling Units Allowed
9,000 SF / 680 = 13.23
You can develop 13 Units on this property.
DENSITY FACTOR KEY POINTS TO CONSIDER
- You can only round up Density Factor if you have a value with .75
- DU is not based off of the Building Floor Area but rather the Zoning Allowable Floor Area.
- “Small zoning lots“ are restricted to 1 and 2 families even if the density factor allows for more then 2.
- Buildings with “Micro Units” must still comply with DU Factor.
DWELLING UNIT COUNT
Your maximum unit count will tell you how many apartments you can put on a lot. You can also use it to see if you can expand and existing building to add more apartments to it
Dwelling Unit Factor Zoning
As an architect I study zoning very closely. This blog post covered some of the basics with regards to Zoning DU Factor. This post is a general overview and does not assume to cover every issue or condition. This post is not a substitute for the NYC Zoning Resolution but rather a basic introduction to the topic.
THANK YOU FOR READING OUR POST ON DENSITY FACTOR AND DWELLING UNIT CALCULATIONS.
We hope this post was helpful and we wish you the best of luck with your project. Please feel free to leave comments or questions below. If you are interested in speaking with an architect you can contact us directly.
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 15 years where he has designed renovations and new developments of various building types.