Zero-Clearance Entrances in NYC


The 100 elevator entrances provided by Columbia make both developers and tenants smile.

Start spreadin’ the news: New York City (NYC) has recently added yet another iconic structure to its skyline, this one in the ultra-chic West Chelsea area. Located immediately adjacent to the High Line, at 520 West 28th Street, this property is often referred to as the Zaha Hadid building, an homage to the architect who personally designed it. Embodying Hadid’s futuristic

“mathematically inspired curving buildings” approach, this building was her first residential project in NYC and among the last before her passing in March 2016.

In keeping with its West Chelsea location — a cultural hotspot — the building’s offerings include a number of street-level art galleries and a sculpture garden created with support from Friends of the High Line. Typical of today’s trend toward ultra-luxury environments, the building features amenities such as a swimming pool, a private 3D IMAX screening room and advanced air-filtration system. It also includes 100 elevator entrances provided by Columbia Elevator Products Co., Inc., delivered in prime for customized architectural adaptation to the surroundings of each entrance. Of note is the fact that they all are “zero-clearance” entrances.

The use of zero-clearance entrances has long been a subject of confusion, particularly because they are unique to NYC. Fire-safety codes typically involve Phase I and II. In Phase I, when smoke is detected, all elevators cease up-and-down operation, redirect to the evacuation floor and shut down. In Phase II, firefighters have access to special keys, allowing them to manually assume elevator operation and direct cars to the floor most advantageous to fighting the fire. If, for any reason, the Phase II key is turned off, the door either does not open, or reverses direction and closes.

Everywhere other than NYC, Phase I and II prevent a landing from being locked out of service. NYC became the exception because of its unique real-estate environment, particularly relating to luxury high-rise residential construction and some unique commercial applications. As is often the case, such situations became governed by matters of revenue and profitability. Market forces made it desirable to install elevators exclusive to single-occupancy floors in residential buildings. Initially for penthouses, then for lower-level luxury apartments with private elevator service, building owners and managers sought to sell or rent entire floors, including common areas such as had been customarily allocated to an elevator vestibule. But, accomplishing this while adhering to Phases I and II presented a major problem in that it would make the firefighter’s key easily accessible to potential thieves and allow them access to entire private residences.

A first thought to get around this problem was to locate a key near the single tenant floor, allowing access exclusively to its residents. However, this, in turn, created a much more serious issue: in the event of a fire, the firefighter could not gain entrance. A next thought was to provide all parties access to the exclusive floor but install, in front of the elevator sliding doors, a second, separate swing door that required its own key. While this more aggressively blocked entry by thieves, and a firefighter with an axe could get in, such an arrangement would not be compliant with locked-out-of-service code. After much debate about the amount of space that was safe to create between the two door sets, NYC building code came around to allowing use of a swing door mounted in front of an elevator entrance with sliding doors with the most minimal possible space or gap between them. This created the concept of zero-clearance entrances that could yield the desired additional square footage the real estate developers were endeavoring to sell or rent. Says Louis “L.J.” Blaiotta, Jr., Columbia’s CEO, “While many cities allow a second door in front of the sliding doors as a smoke seal, to the best of my knowledge, NYC is unique in that it permits such swing doors to lock in the closed position.”

To best understand this would be to understand the designs and purposes of the two types of door systems. Explains Blaiotta:

“Fire doors are usually held open by a magnetic catch/switch that retains the swing door in the open position during normal operation. However, upon activation of a fire alarm, the catch is released, and the self-closing swing door closes to prevent smoke from entering the hoistway, using the ‘stack effect’ to move from floor to floor. This is one extremely effective solution and alternative to constructing elevator lobbies at each corridor landing or the use of gasketing, with or without the pressurization of the hoistway. Another is the use of roll-down barriers that can be used to similar effect. All such solutions, including the swinging fire door, do not allow the entrance to be locked out of service. Passengers exiting the elevator cab during a fire will be able to pass through and open the fire/smoke barrier positioned in front of the landing entrance without needing special keys or tools, or encountering an issue of entrapment.”

Zero-clearance doors may be similar in appearance to the fire-/ smoke-barrier doors, but behave very differently and provide different benefits and features. While they can be used to provide additional smoke and fire protection, their primary purpose is security, especially in high-end buildings that may have only one or two apartments per floor. In such supertall, superthin and super-luxurious buildings — where there is typically only one apartment per landing — it is becoming increasingly the case that a “common-space” corridor between the elevator entrance and the apartment’s front door becomes unnecessary. In this situation, the entire corridor can be eliminated by preventing unauthorized entry into an apartment from the elevator.

An ideal way to accomplish this — while at the same time maximizing the interior marketable space of the apartment — is elimination of the exterior corridor, while installing a zero-clearance security door directly at the elevator entrance to the cab. With the addition of such security doors, luxury-apartment dwellers enjoy the effect of living with private elevators that directly service their units without the wasted space of dedicated hoistways for each unit. And, while the addition of the swing door in front of the sliding entrance doors does mean less unusable space and more security, it also means the doors cannot be opened without the use of a permitted key or special tool, and, for that reason, landings used for egress during a fire alarm cannot be fitted with locked zero-clearance doors.

In addition to such residential applications, zero clearance has found its way into the commercial office building environment. Explains Nicholas J. Montesano, president of DTM Drafting & Consulting Services, Inc., an NYC-based vertical-transportation consulting group:

“In view of the ever-changing dynamics of the commercial real-estate marketplace, zero-clearance doors are being utilized to accommodate a growing trend of single tenants occupying multiple floors. As the needs of commercial tenants drift away from once-standard full-floor/bank-block occupancy, new and special requirements are arising for priority and/or express elevators. For example, where executive offices, conference centers or amenity venues are either at the higher portion or middle of a building, there arises a need for specialty elevator service.”

Sometimes, high-rise elevator service is warranted at a low- to mid-floor landing — embodying special features that require priority service — such as when a tenant’s executives require expedited travel to offices and conference rooms in the higher portion of the building. Such landings normally are not for use by the general riding public and normally are restricted to “authorized” passengers only. Continues Montesano:

“One way of addressing this is to install a lower floor stop, usually located within the express zone in the high-rise bank, to accommodate such executives who are authorized, by activation of a card reader, to call the elevator via a priority-service feature. When such priority-service openings are located within the tenant’s space — without the protection of a vestibule to ensure security — the application of a zero-clearance door is warranted. Such doors can be made architecturally unobtrusive by designing them to blend seamlessly into the décor of the office space.”

Regardless of whether the application is residential or commercial, the use of zero-clearance entrances has created concern and discussion about potentially lethal entrapment. This could happen when a person steps out of the car into the very small space between the swing door and sliding doors, then all doors become closed/locked in front of and behind them, leaving them trapped between the two sets of doors. Blaiotta explains:

“Hence, development of the term ‘zero clearance,’ is somewhat of a misnomer, since it is nearly impossible to place a swing door literally 0 in. away from the sliding doors, even though that would absolutely avoid entrapment of any size person or pet. In actuality, the objective is to leave as little clearance as possible between the sliding doors and the locking swing door to minimize that possibility, and, for reasons of practicality, NYC code limits the space to less than 6 in. Nonlocking fire/draft doors need not adhere to this limit, since the exiting passenger can simply open the swing door, thereby eliminating the entrapment issue.”

According to Robert Cuzzi, president of VDA (Van Deusen & Associates), an elevator consulting firm with deep experience in the use of zero-clearance entrances:

“When planning for a zero-clearance door installation, as part of either a modernization project or new elevator installation, it is extremely important to consider and strategize the various options so the entrances can be properly configured and designed to accept the zero-clearance door.”

There are two broad categories in which zero-clearance entrances are employed: namely, fire-rated and nonrated hoistways. Nonrated hoistways include, but are not limited to, open-atrium hoistways, non-fire-rated glass hoistways, open hoistways (such as in parking garages) or on the exterior of a building, etc. — essentially, any hoistway in which there is no need for a label on the elevator entrance. Such nonrated situations allow the use of any combination of jambs and lockable swing door or gate applications, as long as less than 6 in. of clearance exists between the two sets of closed doors. As the name implies, the design simply must limit the clearance between the doors to safeguard against possible entrapment.

Fire-rated hoistways, on the other hand, are a bit more complex. Since entrances are certified as UL-labeled only when installed in the same end-use configuration as tested in the certifying agency’s laboratory, it is necessary to find an entrance manufacturer that has tested its sliding entrance with a swing door attached in the type of wall system tested. Continues Cuzzi:

“While, in nonrated hoistways, some tenants do sometimes add zero-clearance swing doors after the installation, it is far preferable to have the entrance designed and configured to accept the new door. This better ensures that the maximum code dimensions (6 in. between the inside faces of the elevator landing door and zero-clearance door) are adhered to and the lock cylinder is accessible from inside the cab, as prescribed by NYC code. In rated hoistways after the entrance is installed, modification of an entrance for a zero-clearance door must be avoided: altering an existing entrance, or ‘cutting into it,’ can affect the fire and UL ratings of the new entrance.”

Finding a fire-rated entrance that can support the additional swinging security door is simpler in masonry applications, where there is no labeling requirement for the jamb/frame. In this case, either the sliding door or the zero-clearance swinging security door must bear a UL label. The more common application is for the sliding elevator door to bear the fire-rating responsibility and carry the UL label, as this arrangement allows for more flexibility with the swinging security door, which may be attached directly to the sliding entrance frame. In this design, since the sliding door bears the fire-rating responsibility for the hoistway, the security door does not need to be rated or, even, to be a solid door (and may, for instance, instead be a security gate).

A drywall installation becomes a bit more difficult to design. As above, best and easiest is to use a fire-rated sliding-entrance manufacturer that has successfully tested its sliding entrance with a swing door attached to the jamb. In this case, the sliding door and/or swinging door may bear the UL label to protect the fire integrity of the hoistway. In situations where the entrance manufacturer has not tested its assembly in this manner, a fire-rated swing-door entrance with its correspondingly rated swing door can be installed in the landing wall to protect the hoistway. In this case, the sliding elevator landing doors are not fire rated and only act as a hoistway barrier for fall protection should the swing door be opened while the elevator car is stopped at an alternate landing. Since the sliding doors are not the ones responsible for the fire protection, the swing door must be self closing to ensure its rating.

The alternate/reverse situation also applies here. A fire-rated sliding-door entrance may be used with its fire-rated drywall jamb and fire-rated sliding doors in combination with another, completely separate swing entrance. In this case, the sliding doors bear the responsibility for protecting the rated hoistways, and the swing door does not have to be rated, or, again, even solid. However, unless the sliding entrance was tested with a swing door attached to its jambs, the swing door may not be attached to the sliding entrance frame in any way, or it will violate the UL label. Instead, in this case, a second swing-door entrance assembly, complete with its own frames and doors, must be installed directly in front of the rated sliding-door assembly but make no permanent fastening/connection between the two entrances. Since the code-mandated 6 in. or less of clearance must be maintained between the two sets of doors to eliminate entrapment, it is easiest to deploy this configuration in very thin drywall systems. Otherwise, additional measures must be taken, including addition to the back of the door of entrapment-eliminating filler panels. Adds Cuzzi: “Clearly, proper planning can avoid potential issues and mistakes later and help ensure that property owners/managers understand what they are purchasing and how it will operate.”

Montesano observes that the industry is demanding more versatility from all aspects of vertical-transportation systems, and the zero-clearance door is a growing option. Blaiotta states that, while the use of zero-clearance entrances prevails in NYC, it must be noted that there are concerns on the part of other jurisdictions about the “locking-out-of-service” of an elevator entrance, and possible dangers to firefighters and elevator passengers subject to entrapment:

“My purpose and objective here are not to debate these issues, but rather to illustrate the proper and safe use of zero-clearance barrier doors where current code allows them to be installed. With the growing trend toward supertall, super-slim residential buildings and single tenants occupying multiple floors in commercial buildings, there will be many more such situations requiring heightened sensitivity to these issues. But one positive consequence I have been seeing is this: rarely is there one set of circumstances that makes both the real-estate developers and tenants happy, but this is one of them. The developers like the additional revenue these installations allow, while tenants enjoy the additional living and/or working space and what they can do with it!”

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Elevator World | March 2021 Cover