Depending on the context, the Floor Area for a project is calculated using different metrics –
e.g., gross floor area, zoning floor area, and net floor area. Under the Inclusionary Housing
(“IH”) Program, as administered by the Department of Housing of Preservation and
Development (“HPD”), both Zoning Floor Area (“ZFA”) and Net Square Footage (“NSF”) are
crucial metrics when calculating the amount of Affordable Housing Floor Area (“AHFA”) that a
project is required to provide, and is generating, in order to receive the zoning bonus (under
the voluntary program) or be permitted to build on the site (under the mandatory program). It
is important to understand which areas count towards the calculation of the AHFA and which
ones do not.
When determining the amount of AHFA that a project is required to provide, the calculation is
made based on the proposed ZFA of the project. In contrast, when determining the amount of
AHFA that a project is actually generating, the calculation is done using both ZFA and NSF
To properly calculate the NSF of an affordable unit, the project must consider the floor area
within the perimeter of the unit’s walls, including carpet areas, closets, and the partitions that
separate each room within the unit. For this calculation, the architect must exclude items such
as the thickness of exterior walls and the thickness of partitions separating a unit from any
other units or spaces.
The calculation to determine the amount of AHFA that a project is generating not only includes
the NSF of all Inclusionary Units, but also a percentage of the hallways and other common
spaces in the project. As such, the calculation considers common spaces for which a user fee is
charged, and the AHFA generated by a given project will increase or decrease based on whether
the common areas in the project are considered a ZFA and whether fees are charged for its use
– it being understood that charging for amenities not considered ZFA, such as the cellar, will not
impact the AHFA calculation.
Calculating the AHFA correctly to ensure your project is providing the required amount of
Affordable Housing Floor Area in order to comply with the NYC Zoning Resolution is the first
and most important step when developing an Inclusionary Housing project. If you are
interested in learning more on this subject or have any questions, please contact Alvin Schein or David Shamshovich.