Converting To Multi Family NYC

by | Last updated Jun 4, 2020 | Multifamily Residential, NYC DOB

Many people who own single family and two family homes are interested in converting them to multi family apartment buildings. Any building with three or more residential units is considered multi family in NYC. In this post, we will explore some of the requirements for converting from a 1 or 2 family house into a multi family building. These regulations are based on New York City Building Codes.


Converting To Multi Family 

The first thing I want to tell you is that this may be more complicated then you think. Lets start with a list of some basic requirements, and then we will go into detail on when each is necessary.


  • Zoning
  • Elevator
  • Fire Alarm
  • Fire Sprinklers
  • ADA Accessibility
  • Construction Classification
  • More than 1 Means Of Egress
  • Alteration Type 1 


Zoning Requirements For Converting To Multi Family in NYC

NYC has different zoning districts that determine what you can build. If you own a one or two family home, you need to be in a zoning district that allows multi family use in order to convert your home. So the first thing is to verify you are in a multi family residential zoning district. If you are in a commercial zoning district you need to look up the Residential Equivalent Zoning. Once you have determined your zoning district allows for multi family, then you need to figure out the density factor. Every zoning district has a formula that determines the maximum allowable number of dwelling units. A ‘dwelling unit’ is code speak for an apartment. I am not going to go deep into this calculation. You also need to make sure you are okay with the minimum lot sizes for multifamily.

An architect like me can help you with all of this. You can always get a Zoning Analysis on your property to see the development potential. At our Architecture Firm In NYC, we do these types of zoning analysis and building conversions all the time.

Conversion, Addition, or New Building

It may be the case that you have the ability to build an addition to your building. Sometimes it makes sense just to tear down the whole house and start from scratch. But if the structure is appropriate you may look into building an addition. We wrote another post on Building Additions if you want to learn more about that. You have to figure out what makes sense: converting, building an addition, or demolishing and building a new building.

Building Addition and Conversion to multifamily

Building Addition and Conversion 2 family with addition to multifamily.


Elevator Requirements for Multi Family Conversions

If you convert to a multi family and you do an addition with a total of 5 stories or more, you will need an elevator. All multi family buildings over 4 stories require an elevator. You can have a top floor mezzanine that does not require an elevator.

If you do have an elevator, then every apartment will be required to be ADA / handicapped accessible.

By the way, basements count as a story but a cellar does not. Basements are less then 50% underground. A Cellar is more than 50% underground. See another blog post we wrote on the difference between a cellar and basement.


Fire Alarm Requirements For Your Building Conversion

If you have 4 stories, you will need a fire alarm. I do not believe there are any exceptions to this. Any building over 3 stories requires a fire alarm, as per NYC building codes. Fire alarms are not really that expensive, relatively speaking.


Fire Sprinklers Required

Do you need fire sprinklers when converting a 1 or 2 family house into multi family ?

In New York City, fire sprinklers are always required when converting 1 or 2 family homes into 3 or more family, multi family buildings.

I am going to say this again because people always seem skeptical about this when I tell them. YES, you will need to install fire sprinklers. No exception. End of story. I am not going into any detail here. Even after I tell them it’s required people are constantly asking me if they can get away without putting in sprinklers – no you can’t. Put fire sprinklers in the building.


ADA Accessibility – Handicapped Accessibility

If you are going from 1 or 2 families to multi family, you will be required to have handicapped accessibility. ADA or Americans with Disabilities Act is a federal law requiring accessible access.

In new buildings or conversions with an elevator, all apartments must be ADA accessible.

In new buildings or conversions with no elevator requirement, all units on the first floor must be ADA accessible.

This means if you have an existing first floor above grade (with stairs going up), you may have a problem. In these instances, it often makes sense to demo the building or reconfigure the floor elevations. Speak to an architect about your options.


Construction Classification

All buildings fall into a construction classification. You need to figure out if your current construction classification is acceptable for a multi family building. You need proper fire ratings for floors, walls, roof, columns, etc…

If your home is wood framed, you will not be able to convert it to multi family. You should demo the house and build a new building. Talk to your architect about the construction classification requirements.


Means Of Egress

Means of egress are exits and stairs. This is linked with construction classification. The number of exits and stairs is a factor of the number of stories, number of apartments per story, number of occupants, and the construction classification. This is a little complicated, so you will definitely need an architect to figure this out.


Alteration Type 1

You must file your building conversion as an “Alteration Type 1” with the Department Of Buildings. You must get a new Certificate of Occupancy after construction in order to legally occupy the building. We have another post on Alteration Type 1 applications if you want to read more.


Converting 2-family into 3-family in NYC

It is important to note that when converting 2-family to 3-family, you are switching to multi family. Multi family starts at 3 families. A house is 1 or 2 families. Converting from 1 family to 2 family is a bit easier because you do not need to comply with multi family regulations.


Thank You for reading our Blog Post on Converting To Multifamily.

Good Luck with your building conversion. If you would like to speak with an architect, please feel free to contact us directly. You can also leave a comment or question below.


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 15 years where he has designed renovations and new developments of various building types.