If a proposed building complies with Zoning Codes you can build against your neighbor’s wall. There are codes to comply with and technical issues to contend with, but in general it is allowed to attach a building to your neighbors wall.
Building Against Your Neighbor’s Building
- Zoning Codes
- Side Yard Requirements
- Attached Building Requirements
- Blocking Windows
- Light and Air
- Structural Issues
Attached Building Zoning Codes
Not all Zoning Districts allow Attached Buildings but most do. If your zoning fundamentally prohibits attached or semi-detached buildings then you are out of luck. Most zoning districts in NYC allow them, for example if you are in R6 through R10 Zoning you can build attached to your neighbors building. Also Commercial Zoning generally allows attached buildings in most cases.
NYC Zoning Restrictions for Abutting Buildings
Some zoning restrictions apply for abutting buildings such as in R3-1, R3-2, R4, & R5 Zoning Districts not counting R4A and R5A. These restrictions are as follows:
The neighbors building must abut the property line for at least 50% of its length.
The side yard can be waived for the abutting side. You must provide a side yard on any side that is not abutting.
Blocking Your Neighbor’s Windows
Can you block your neighbor’s windows when building a new building?
Yes If the buildings are on separate zoning lots you are allowed to block your neighbor’s windows. There is no law to stop you unless you have some kind easement or agreement with the neighbor and are in compliance with all zoning and building codes. If they have lot line windows for a residential buildings those windows would not qualify for light and air anyway. This is based on New York City regulations.
Can your neighbors sue you for blocking their windows? People sue each other for all sorts of things. I am sure it happens so make sure to consult with a lawyer if you are concerned. Attaching buildings in NYC is very common so I would not worry much about this. make sure there are no historic agreements with the neighbors from previous owners.
Light and Air for Residential Buildings
Habitable Spaces in Residential Buildings have natural light and air requirements. Windows on a property lines (often referred to as lot line windows) would not qualify unless you do a zoning lot merger with the neighbor.
Structural Issues for Attaching to Your Neighbor’s Building
All buildings should stand independently. You building should not place any load on your neighbor’s building. When you are building up to another building there can be an issue with the foundations that require underpinning.
Foundations for Attached Buildings
When you attach 2 buildings their foundations or footings need to be at the same depth. If one is deeper than the other you will have a structural problem because the higher footing will apply load on the neighbor’s lower foundation wall. This is resolved in one of 2 ways.
Match the Neighbor’s Footing Depth
To prevent problems you can match the neighbor’s footing depth. Before the architectural and engineering team design the structure they will do test pits. This is a dig out to expose a portion of the neighbor’s foundation. They can then design a foundation and footing to match the neighbor’s depth so that there is no structural conflict.
Underpinning Attached Buildings
If you are must build your foundation deeper than the abutting neighbor’s foundation then you have to do underpinning. Underpinning is the extension of an existing foundation deeper into the Earth. That means you literally add to the existing foundation under it. This is a costly and tedious method of construction. What they do is dig out small portions of the soil under the neighbor’s building and little by little pour new concrete underneath it.
When the process is complete you will have lowered the neighbors foundation wall and you can now match your footing to the bottom of their new foundation.
Thank You for reading our Blog Post on Attaching to your neighbor’s building.
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.
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.