Grandfathered Definition for Buildings

by | Last updated Feb 6, 2021 | General Architecture

In Real Estate Development the term Grandfathered means that an existing building does not have to comply with a current zoning or building code because it was legally built before the application of such code.

Buildings can be Grandfathered by existing before a code was written. There are many misconceptions on what qualifies Grandfathered and what does not so we will review some of the basics here. I am an architect in New York any reference to codes in this post will be based on New York codes and protocols. You should check your local requirements as they could vary.


Grandfathered Zoning

Zoning Codes are those codes that dictate the use of a building as well as its bulk (shape and size). In many cases existing buildings built before the current zoning codes were written are Grandfathered. One important issue you must realize is that they are grandfathered as is. If you plan to make certain types of alterations they may no longer be Grandfathered. Or the status as Grandfathered may not apply to certain alterations.

In NYC the Zoning Resolution outlines two types of Grandfathered conditions these are non-complying buildings and non-conforming uses.

Non-Complying Building

A Non-Complying Building is a building who’s bulk does not comply with the current Applicable Zoning Codes. If the building was built legally under an older code then it will be considered Grandfathered. The Zoning Code outlines the applicability of codes in such cases.

An example of Grandfathered building bulk would be if a building has 7 stories in a Zoning District that only allows 6 story buildings. If the taller building was built before the current codes then it would be permissible to remain as is.

Non-Conforming Use 

A Non-Conforming Use is a building that has a use which is no longer allowed in a certain zoning district. If the building was legally built under an older code it may be considered Grandfathered and the use may be allowed to continue. The Zoning Code outlines the applicability of the codes on Grandfathered properties and buildings.

An example of a Grandfathered Use would be the existence of a commercial store in a zoning district that only allows residential use.

Grandfathered Building Code Applicability. 

The Building Code dictates how a building should be built for example fire safety. If a building is Grandfathered it may not have to comply with certain building codes. The building code may explain what is acceptable as a Grandfathered Condition and the Department of Buildings will have the final say on this.

Verification of Existing Conditions

In order to be Grandfathered it has to have been built legally at the time it was built. The Department of Buildings may request proof of the existing conditions.

Also one important thing everyone seems to misunderstand. Buildings are grandfathered as they were built. What I mean is if you make changes to the building you may negate its ability to be Grandfathered. Here is an example. Lets say you have a commercial building that would require fire sprinklers today but it is Grandfathered without sprinklers. This may be ok depending on many factors. But if you want to convert it to a residential building that would require adding fire sprinklers. And then you will say but the building was Grandfathered right? Well it was as a commercial building not as a residential building. So in NYC you would have to add fire sprinklers in this situation.

Unsafe Conditions are not Grandfathered

The Grandfathered rule does not apply to situations that are unsafe. If a building is unsafe it must be made safe.


Grandfathered Buildings

As an architect, I study Building Codes and 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 Grandfathered Definition. 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 Grandfathered Definition.

I hope this was helpful. If you would like to speak with an architect, you can contact us at Fontan Architecture 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.