Zoning and land use
Floor area ratio and how much you can build
Floor area ratio multiplied by lot area sets the buildable floor area. Here is how it is calculated, what is excluded, and why the zoning lot is the real unit.
What is floor area ratio and how do you tell how much you can build?
Quick Answer
How much may be built
Who does this land on?
Developers, owners considering an addition, and buyers paying for unbuilt development capacity that may already have been used.
What governs it?
- The district bulk regulations in the Zoning Resolution, which set the maximum floor area ratio for each use
- The definition of floor area, which excludes certain cellar space, mechanical space and other categories by rule
- The definition of zoning lot, which can combine several tax lots under common ownership or a recorded agreement
- Bonus provisions, including the inclusionary housing program, which permit additional floor area on stated conditions
- The Department of Buildings zoning analysis on each filing, which is where the calculation is tested
How does the process run?
- Establish the zoning lot, which is the question a survey and an ACRIS search answer, not the tax map alone
- Measure the lot area, and confirm it against a current survey rather than a listing
- Apply the district floor area ratio for the intended use, remembering that residential, commercial and community facility ratios differ in the same district
- Subtract the floor area already built on every tax lot in the zoning lot, including neighbors if the lot was merged
- Apply the exclusions and any bonus the project qualifies for, and document each one in the zoning analysis
- Test the result against height, setback, yard and open space rules, which often bind before the floor area does
Where does it bite in a transaction?
- A lot is priced on its own unused floor area when a recorded merger already moved that capacity next door
- An addition is designed to a ratio that applies to a different use than the one proposed
- Cellar space is counted as excluded when the grade condition does not support the exclusion
- A building already exceeds the current ratio, so the addition is not an addition but an enlargement of a non-complying building
Is the zoning lot the same as the tax lot?
Often, but not reliably. A zoning lot can combine contiguous tax lots in single ownership, or lots joined by a recorded declaration and zoning lot development agreement. Because floor area is calculated across the whole zoning lot, buying one tax lot out of a merged zoning lot can mean buying no development capacity at all.
What happens if a building already exceeds the permitted floor area?
It is a non-complying building rather than an illegal one, assuming it was lawful when built. It can generally remain and be maintained, but enlarging it, and sometimes rebuilding it after major damage, is restricted. That is a different analysis from a non-conforming use, and the two are frequently confused.
Does every square foot inside the walls count?
No. The Resolution defines floor area and excludes stated categories, including certain cellar space and mechanical space. Exclusions are technical and they are the part of a zoning analysis a plan examiner reads hardest, so they are documented on the drawings rather than asserted.
Can you buy more floor area?
Sometimes. Unused development rights can move between lots through a zoning lot merger, and specific Resolution provisions allow transfers from landmarks and within certain special districts. Those are recorded real property transactions with their own diligence, not a line item on a budget.
What else should you read before you file or sign?
In the glossary
- Zoning lot certificateA recorded declaration combining tax lots into one zoning lot for development purposes. Waivers and consents from affected owners and lienholders a...
- SurveyA surveyor's drawing of the parcel, its improvements and any encroachments. Lenders on houses and townhouses generally require a current one or a s...
- Survey readingReview of an existing survey to confirm it still matches the property and the record. It determines the wording of the survey exception on the policy.
- BBL (Borough-Block-Lot)The tax lot identifier for a parcel of New York City real property, written as borough, block and lot. Nearly every City record system keys on it r...
- AppurtenanceA right or improvement that passes with the property when title transfers, such as an easement benefiting the parcel, a parking right or a fixture ...
Zoning and land use
- Air rights and transferable development rightsAir rights move three ways in New York City: a zoning lot merger, a landmark transfer, or a special district mechanism. Each is a recorded real est...
- Zoning lot mergersA zoning lot merger joins separate tax lots into one zoning lot so floor area can move between them. It is recorded, and it binds every future owner.
- R, C and M zoning districts in New York CityEvery NYC lot sits in a residential, commercial or manufacturing district, often with an overlay or a special district on top of it. Here is how to...
- Area varianceAn area variance asks for relief from bulk rules: floor area, height, setback, yards, parking. Here is how it differs from a use variance and what ...
- Zoning due diligence before you signSix records answer almost every zoning question on a New York City property, and all six can be pulled before the contract rather than after the de...
The violation code
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Legal Disclaimer: This page is general information about New York practice. It is not legal advice, it does not account for the terms of any particular contract, building or transaction, and reading it does not create an attorney-client relationship. This is attorney advertising. Prior results do not guarantee similar outcomes.