The Department of City Planning (DCP), in collaboration with the Department of Buildings (DOB) and the Fire Department (FDNY), is proposing a city-wide Zoning Text Amendment to facilitate and make effective additional safety measures that are part of New York City’s 2014 Building Code.
As part of the 2014 update to the New York City Construction Codes, new safety measures were incorporated for high-rise non-residential buildings. These safety measures are intended to enhance public safety in new high-rise buildings by providing additional exiting capacity for building occupants during emergency situations that require full building evacuation. These safety recommendations resulted from an extensive study by the National Institute of Standards and Technology of the World Trade Center disaster.
The report recommended several changes to model buildings codes around the country:
- Decrease the time it takes to evacuate an entire building in an emergency
- Increase the ability of first responders to access building occupants
- Providing greater redundancy in escape routes to ensure that, should one such route become unavailable for building occupants, there is still adequate capacity to exit or evacuate the building.
These recommendations were incorporated into the 2009 International Building Code and were adopted into the NYC Building Code as part of the 2014 NYC Construction Codes (PDF Document Local Law 141 of 2013). The law stipulates, however, that these safety provisions will only become effective once a text amendment is approved to exempt the space occupied by these features from counting towards zoning floor area.
The proposed text amendment consists of an amendment to the New York City Zoning Resolution, Section 12-10 (Definitions), to exempt floor space that is occupied by these additional safety measures from counting towards zoning floor area (zfa).
These safety measures are required for all new non-residential buildings that are greater than 420 feet in height, or mixed use buildings that contain non-residential space above a height of 420 feet. Predominantly residential and fully residential buildings are not subject to the additional requirements and are not affected by this text amendment.
This amendment will not affect a large amount of buildings: an examination of DOB records shows that from 1997-2014, only 29 non-residential buildings over 420 feet tall were constructed, which is equivalent to less than 2 buildings per year.
Buildings of this size are typically found in zoning districts without set height limits that allow a floor area ratio (FAR) of 10 or greater. These districts can be found in midtown and downtown Manhattan, downtown Brooklyn and portions of Long Island City in Queens.
Briefly summarized, Building Code Section 403.5.2 is a new provision requiring one of the following options be incorporated into the design of all new non-residential buildings greater than 420 feet in height:
- Construct all passenger elevators in the building as “occupant self-evacuation” type, including the safety requirements of such elevators, such as connection to emergency standby power, emergency communications, and special lobby dimensions to accommodate floor occupants, including wheelchairs; or
- Increase the required width of all “emergency” exit stairways by 25 percent above what is otherwise required and construct all passenger elevators as “occupant self-evacuation” type but the standby power generating-equipment need only be sized to accommodate a limited number of the elevators (defined by an approved timed egress analysis); or
- Construct one additional “emergency” exit stairway than is normally required based on the number of building occupants.
The above requirements resulted from mediation that included all stakeholders in both the Egress and Elevator Technical Committees, and are based on those adopted in the International Building Code.
Depending on the design option selected from the Building Code requirements, the reconfiguration of total net floor area could result in slightly bulkier buildings; either with slightly larger floorplates, or slightly increased height. To understand the net effect of this change, the Department studied building types most likely to be affected by the proposed amendment. Of the 29 non-residential buildings over 420 feet in height that were built in the past 15 years: 18 are office buildings, 10 are hotels, and 1 is a hospital. Therefore office and hotels are the primary types of high-rise development affected by this action and were the focus of our analysis.
The diagram below indicates the typical fire safety exit stairways found in high-rise office and hotel developments. It illustrates the amount of floor space taken up by the additional safety exit stair (184 square feet per office floor or 141 square feet per hotel floor) and the amount of floor space taken up by the 25% increase in width of the current stairways (52 square feet per office stairway; 47 square feet per hotel stairway), using typical floor to floor heights in each building type.
Small Floor Plate Buildings (less than 10k sf)
Buildings with small foot plates have a tight building core, and usually a small number of elevators are adequate to serve the building occupants. Because of the limited amount of square feet per floor, the designers of such buildings typically seek to maximize the amount of usable square footage. The provision of all occupant self-evacuation elevators (OEEs) occupies the least amount of usable floor area per floor, thus maximizing efficiency, and would therefore be the most likely design option for these small footprint buildings. The fact that fewer elevators are provided in small floor plate buildings, construction cost associated with adding the OEEs is also less. There is no floor area exemption for that option, however, on the small footprint office building shown here, even the maximum floor area deduction associated with an additional stairwell results in less than ¾ of an additional floor.
Medium Floor Plate Buildings (10k-15k sf)
By contrast, high-rise buildings with medium and large floorplates need significantly more elevators to efficiently transport the building occupants. Therefore, the added cost for all OEEs is greatly multiplied and the provision of backup power for all the elevators is more expensive as well. Overall, development sites with larger floorplates allow the project designer a greater amount of design flexibility. The designer of these buildings would most likely choose either the 25% wider stairways with OEEs or the additional exit stairway. The medium floor plate building shown, typical of larger hotels, results in between one-half and three-quarters of an additional story.
Large Floor Plate (greater than 15k sf)
The larger floor plate buildings will most likely choose the additional stair requirement because of the large efficiency of this floor plate size. However, the resulting exempted square footage is less than half of a story because of the large size of the building.
The proposed text amendment was referred out on November 17, 2014 for 60 days to all affected Community Boards, Borough Boards and Borough Presidents for review and comment.
The proposed text amendment is being referred to 11 Community boards (8 in Manhattan, 2 in Queens and 1 in Brooklyn), the 3 affected Borough Presidents and the Manhattan and Queens Borough Boards.
Images courtesy of Department of City Planning New York City