Key Project Terms: Alterations: Multiple Dwelling Unit Buildings

The following is a list of useful terms to use when researching additional Residential & Community Facilities information on each of the topics discussed:


The design and construction of buildings for accessibility and use by persons with physical disabilities, complying  with the Federal ADA Standards; US Housing and Urban Development (HUD); BC Chapter 11, BC Appendices E, N and P; and/or ICC/ANSI A117.1.


An alteration is the addition, change of use, or occupancy of a building or structure in existence, and always results in a new or amended Certificate of Occupancy. Work may involve an enlargement, reduction in size of the building, or a major change to the building egress, zoning use group, and/or building code occupancy use.

Building Systems Work

The installation, modification, or upgrade of existing building systems including plumbing, boiler, sprinkler, standpipe, fire alarm, HVAC, and fire suppression systems. If such repairs are part of the project, they must be included in the scope of work.

Certificate of Occupancy

A new or amended Certificate of Occupancy is issued for a building on completion of a project involving a change in occupancy or use, or when there are other changes that impact the existing Certificate of Occupancy. For example, where an existing building is vertically enlarged by a complete story, or if the use of a building is changed from commercial to residential, a new or amended CO would be required. Reference AC 28-118.3 for more information.

The following may also be issued:

  • A Partial Certificate of Occupancy, for a portion of a building erected prior to January 1, 1938, depending on construction progress and safety;

  • Temporary Certificate of Occupancy, for a limited duration of time, because the project is not closed due to outstanding items, such as final surveys not submitted, etc., per AC 28-118.16.

Code and Zoning Determinations

Determination requests are issued to the Borough Commissioner's office for an objection raised by a plan examiner or a possible future objection for an application not yet filed (pre-determination). To request a determination, file a Zoning Resolution Determination Form (ZRD1 Form) (ZRD1 Instructions) or a Construction Code Determination Form (CCD1 Form) (CCD1 Instructions). Forms must be signed and sealed by a professional. Determination requests are limited to one per form and must cite all related code or zoning sections


Per the Zoning Resolution, Commercial, as applied to a building’s use, is any retail, service or office use. Commercial can also describe the type of zoning district. Other occupancy classifications in the BC are considered commercial and are listed under Mercantile (M) or Business (B). Refer to Commercial Building Guidelines for additional information.


Per the Zoning Resolution, a conversion is a change of use. A use is any purpose for which a building, structure, or open tract of land is designed, arranged maintained or occupied.

Development Rights

Development rights generally refer to the maximum amount of floor area permissible on a zoning lot. When the actual built floor area is less than the maximum per­mitted floor area, the difference is referred to as “unused development rights.” Unused development rights are often described as air rights.


Per the Zoning Resolution, an enlargement is an addition to the floor area of an existing building or zoning lot, or an expansion of a use to an area not previously used for such purpose.

Per the Building Code, an enlargement is any addition of gross floor area to a building.

Elevation in Flood Zones

Elevating a building to ensure that lowest occupied floor is above the flood levels, per FIRMS, and as described in BC Appendix G and ZR Article VI.

High Rise Building

A building with an occupied floor located more than 75 feet (22 860 mm) above the lowest level of fire department vehicle access.

Layout Changes

Include changes to floor layouts that add, relocate, remodel, enlarge or reduce the size of interior rooms while maintaining the same building envelope.


A loft is a building or space within a building designed for commercial or manufacturing use, generally constructed prior to 1930. In certain manufacturing districts, lofts may be converted to residential use by CPC special permit.

Lot Line Windows

Windows of a building exterior wall located on the side or rear property zoning or tax lot lines. Such lot line windows require special code compliance review, dependent on the building type and building construction class, to determine the allowable window sizes, quantity, and fire protection needed.

Major Building

An existing building 10 or more stories or 125 ft. or more in height, or an existing building with a building footprint of 100,000 sf. or more regardless of height, or an existing building designated by the commissioner due to unique hazards associated with the construction or demolition of the structure.

Mixed Building

Per the Zoning Resolution, a mixed building is a building used partly for residential use and partly for community facility, and/or commercial use.

Mixed Use

Per the Building Code, a building with mixed occupancy would contain two or more occupancy classifications. Such occupancy classifications may or may not match the zoning use groups.

Multiple Dwellings

A multiple dwelling is a building occupied as a residence, with three or more dwelling units, whose occupants live independently of each other. It shall not include a hospital, convent, monastery, asylum or public institution

A Class A Multiple Dwelling is a multiple dwelling that is occupied only for permanent residential purposes (occupancy of a dwelling unit by the same person or family for 30 consecutive days or more), such as, but not limited to an apartment building.

Each Class A Dwelling Unit or apartment must have its own kitchen or kitchenette and its own full bathroom.


The purpose or activity for which a building or space is used or is designed, arranged or intended to be used.

Occupancy Classification

The use as defined in the Building Code, and is the purpose or activity for which a building or space is used or is designed, arranged or intended to be used

Partial Demolition

Maintaining the same building envelope, any construction that involves the removal, replacement or repair of load bearing and/or non-load bearing interior partitions, changes to structural elements (interior or exterior), and facade changes or other upgrades.

Privately-owned Public Space (POPS)

An amenity provided and maintained by the property owner for public use, usually in exchange for additional floor area. Located mainly in the high-density, central business districts of Manhattan, these spaces are typically in the form of an arcade or a public plaza with seating and landscaping and may be located within or outside a building.

Public Plaza

A public plaza is a privately owned open area adjacent to a building and accessible to the public. It must generally be at the level of the sidewalk it adjoins and be unobstructed to the sky except for seating and other permitted ameni­ties. In certain high-density zoning districts, a floor area bonus is available for the provision of a public plaza.

Quality Housing Program

The Quality Housing Program, mandatory in contextual R6 through R10 residence districts and optional in non-contextual R6 through R10 districts, encourages develop­ment consistent with the character of many established neighborhoods. Its bulk regulations set height limits and allow high lot coverage buildings that are set at or near the street line. The Quality Housing Program also requires amenities relating to interior space, recreation areas and landscaping.

Registered Land Surveyor

A person licensed and registered to practice the profession of land surveying under the education law of the state of New York.


Changes to an existing building, including the remodeling or replacing of outdated or damaged structure and materials, and the partial demolition of interior partitions. Building renovations can also include the installation or replacement of building systems, devices or equipment, materials or parts, as part of regular maintenance of the building. Renovation projects do not impact the existing means of egress, do not change the use of the building or space, and do not increase the occupant load.


Per the Building Code, Residential Group R includes the use of a building or structure, or a portion thereof, for dwelling or sleeping purposes. If there are three or more dwelling units in the building, it shall be classified as a multiple dwelling and is subject to the MDL. Residences can be either transient, in which the occupancy of a dwelling unit or sleeping unit is not more than 30 days, or non-transient, and therefore, could include community facilities with sleeping accommodations.

Per the Zoning Resolution, Residential, as applied to building use, is a building with one or more dwelling units or rooming units, but with exceptions; for example, hotels and community facilities with sleeping accommodations are not residences per the ZR. Residential can also describe the type of zoning district; for example, hotels are not allowed in residential districts, while community facilities can be located in residential districts.

Sky Exposure Plane

A sky exposure plane is a virtual sloping plane that begins at a specified height above the street line and rises inward over the zoning lot at a ratio of vertical distance to horizontal distance set forth in district regulations. A building may not penetrate the sky exposure plane which is designed to provide light and air at street level, primarily in medium- and higher-density districts

Sliver Building

A tall building or enlargement that is 45 feet wide or less, in an R7-2, R7X, R8, R9 or R10 district, is commonly called a sliver building. Such buildings are generally restricted to a height equal to the width of the abutting street or 100 feet, whichever is less.


A story is a floor level in a building that is significant in both the Code and Zoning. For example, if a third story is added to a one or two family home, it could trigger additional fire protection requirements in the Code. Basements are stories, while cellars are not. An attic may be considered as a story.

Transfer of Development Rights (TDR)

Allows for the transfer of unused development rights from one zoning lot to another in limited circumstances, usually to promote the preservation of historic build­ings, open space or unique cultural resources; for such purposes, a TDR may be permitted where the transfer could not be accomplished through a zon­ing lot merger. In the case of a landmark building, for example, a transfer may be made by CPC special permit from the zoning lot containing the designated landmark to an adjacent zoning lot or one that is directly across a street or, for a corner lot, another corner lot on the same intersection.


The public review process, mandated by the City Charter, for all proposed Zoning Map amendments, special permits and other actions such as site selections and acquisitions for city capital projects and disposition of city property. ULURP sets forth a time frame and other requirements for public participation at the Community Board, Borough Board and Borough President levels, and for the public hearings and determinations of the Community Boards, Borough Presidents, City Planning Commission (CPC) and City Council. Zoning text amendments follow a similar review process, but without a time limit for CPC review.


The purpose for which a building, structure, or space is occupied or utilized, unless otherwise indicated by the text; Use (used) shall be construed as if followed by the words ‘or is intended, arranged, or designed to be used.’

Use Group

The use as defined in the Zoning Resolution, Section ZR 12-10, and is any purpose for which a building or other structure, or an open tract of land, may be designed, arranged, intended, maintained or occupied; furthermore the use is any activity, occupation, business or operation carried on, or intended to be carried on.


Areas of land are divided into zones within which various uses are permitted.

Zoning Lot

A zoning lot is a tract of land for which specific zoning regulations apply. A zoning lot does not have to coincide with a tax lot, and can consist of one tax lot or multiple tax lots

Key Points & Project Terms Categories

  1. Alterations

  2. Building Systems Installation & Modifications

  3. Construction Equipment

  4. Demolition COMING SOON!

  5. New Buildings COMING SOON!

  6. Renovations

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