Horizontal Sliding Fire Doors: Architectural Design Freedom

Special-purpose horizontal sliding accordion or folding door assemblies allow freedom of design while meeting egress requirements found in IBC and NFPA

By Karin Tetlow

Since successfully passing Underwriters Laboratories (UL) fire-rating tests in 1977, self-closing horizontal sliding accordion-type doors have long been sought as a solution to meeting fire requirements in certain applications. But 20^th century codes did not accept them as a complete solution for meeting fire and building code egress regulations. Design professionals were often required to specify standard wood- or steel-framed hinged swinging doors to serve as emergency exits and to separate internal spaces. Since 2000, however, significant code changes have greatly expanded the use of horizontal sliding door systems. Today, these systems are universally accepted as meeting both fire and building code regulations in virtually any application. (The exceptions are certain applications categorized as Group H occupancies that typically include the storage of flammable and toxic materials.)

Yet many design professionals remain unaware of these code changes and the significant architectural possibilities resulting from their across-the-board code acceptance—and the implications of incorporating sliding door systems early in the design stages.

Sliding door systems play an increasingly key design role where there is a need to have openings that exceed the 4 or 8 feet provided by conventional fire-rated single- or double-swing doors. Moreover, free from the limitations of rectilinear footprints, architects are now able to design fire-rated extended spans and curved openings for an almost endless number of applications. There are many application examples in the United States and abroad. Installed in a multitude of building types, they are found in schools, churches, high-rise office buildings, casinos, airports, senior living facilities, health-care facilities, shopping malls, hotels, public transit, and museums—often at lower costs than for other solutions. With an increased focus on building security since 9/11, government offices, embassies, schools, and courthouses are also increasingly turning to sliding door systems as protection in emergency situations.

From the Venetian Macao, the $2.4-billion anchor luxury hotel on the Cotai strip in Macao, China, to Frank O. Gehry’s Guggenheim museum in Bilbao, Spain, sliding door systems also offer an innovative solution to the code constraints of creating iconic and unique architecture.

Sliding door systems provide an eminently practical means for quickly moving people through an unobstructed exiting system of a building. Repeated testing for use by occupants with disabilities and in wheelchairs has demonstrated that the sliding door system is far more effective when evacuating people from a building than a side-hinged or swing door. Swing doors clearly present user problems in building emergency situations, both for people in wheelchairs and on foot, particularly in crowded situations and when fire and rescue personnel are coming through the door from the opposite direction. Manufacturers have researched and developed sensors and precision microprocessor technology that opens and closes the sliding door with ease. In an emergency, a person with disabilities or in a wheelchair touches the fire exit hardware; the door opens to a preset width, allowing the person to egress, and then recloses, protecting the opening. “The fire-rated horizontal sliding door is the best way to move people through fire barriers during any type of building emergency—whether or not they have a disability,” says Edwina Juillet, co-founder, National Task Force on Fire and Life Safety for People with Disabilities.

How Do They Function?

Horizontal fire-rated accordion-type sliding doors are custom-designed to be stored in shallow recessed pockets in walls. Monitored and controlled by electronic systems, they self-close in the event of fire. In addition to there being no restrictions on the width of the size of openings in UL listings, sliding door systems can reach a 2008 UL-approved maximum height of 28 feet (taller applications, however, can be considered on a case-by-case basis). Moreover, because no floor track is required, they may be specified for radial configurations. With track detail recessed above the ceiling and accordion doors that fold to just inches per foot behind a pocket door, they are virtually invisible until activated. Sliding fire door systems are not applicable in openings designed for doors that are normally closed.

A typical horizontal sliding door system employs a two-track system. Door panels are manufactured from 24-gauge steel and weigh 5¹/₂ pounds per square foot. Panels are 4¹/₂ inches wide, corrugated for strength. Between the two tracks is a 6-inch to 8-inch dead air space.

The door assembly suspension and driver systems are independent. Panels are suspended from an overhead track with a steel pin and roller assembly to increase durability and to make maintenance easier. The door can be completely repaired in place because individual panels may be removed and replaced.

Door assemblies have separate UL listings according to their fire rating, which is determined by building and fire codes. These are 20 minutes, 1 hour, 1.5 hours, and 3 hours (20, 60, 90, and 180 minutes.)

The sliding door system is designed to remain in the open position. Upon a signal from the building fire alarm panel, smoke alarm, fire alarm, a manual pull station, or, in some instances, the activation of a sprinkler flow valve, the door will automatically close. Opening and closing speeds are regulated by National Fire Protection Association (NFPA 80, Chapter 9) Code, which requires speed of not less than 6 inches per second and not to exceed 24 inches per second. The typical rate of opening and closing is between 8 and 9 inches per second. At this rate of speed, a clear opening width of 80 to 90 inches can be created in 10 seconds.

The door assembly’s sophisticated electronic control system operates on a 120-volt AC system that includes a backup battery system and microprocessors that continuously monitor the door systems. The 120-volt line is connected to a junction box in the storage pocket near the control box and continuously charges the battery. Upon activation, a high-decibel sound indicates that the system is in fire mode, and the door closes. If the leading edge of the door, equipped with a special sensor, encounters an obstruction, it will stop, pause momentarily, and then continue closing. Only light pressure on the leading edge is required to cause the door to stop.

When in the closed position, it can be reopened easily from either side. Only 3 to 5 pounds of pressure on the exiting hardware cause the door to retract a certain preset distance (typically 36 inches), pause, and recycle to the closed position. The retractable distance was originally designed in conjunction with California Department of Rehabilitation engineers who were studying methods for evacuating persons with disabilities from multistory buildings during fire emergencies. Most manufacturers set the force to open at 5 pounds or less to comply with Americans with Disabilities Act (ADA) requirements for fire doors in egress applications. The distance the door retracts can be adjusted in the field.

Resetting the door assembly can be accomplished by pushing the open/close rocker switch on the leading edge of the door to the close position. When not in fire mode, this control can also be used to position the door as desired.

The typical sliding door system is designed, UL-listed, and installed so that it does not close upon power loss in the building, unless the loss of power is for a sufficiently long period of time that the voltage in the battery falls to around 11 volts. In typical openings, the door is capable of completing well over 50 complete opening and closing cycles on battery power alone. The door is also designed to be operated manually.

Because the door’s drive system is structurally independent of the door’s suspension system, any force applied to the door’s surfaces will not obstruct the functioning of the door. Nor will any likely substantial deflection of the door have more than a minimal effect on the door’s opening or closing. Logic circuitry in the control unit prevents the door from opening when heat sensors detect a high temperature or fire condition on either side of the door.

Design Possibilities

By allowing openings to appear unencumbered, sliding door systems provide practical answers to fire and egress code requirements while allowing extraordinary architectural versatility. Many museum architects have determined that horizontal sliding door systems solve the problem of meeting fire and building codes while maintaining open vistas between large vertical and horizontal internal spaces. For the Bilbao Guggenheim Museum, Gehry Partners used 10 fire-rated horizontal accordion-style sliding doors totaling 3,000 square feet to deliver interior spaces that aptly reflect the dramatic forms of the exterior. For the J. Paul Getty Museum at the Getty Center in Los Angeles, Richard Meier and his firm Richard Meier & Partners specified 64 doors or more than 6,600 square feet of sliding doors as invisible fire breaks that allow people to move freely between the exhibition spaces.

Sliding door systems have a range of applications in a multitude of building types. Some serve several code-compliance functions at once, such as providing exits and protecting vertical openings, elevator lobby separations, and remote security monitoring capabilities, plus permitting multilevel fire-rated design features. In sum, they provide “area separation,” a reference much in use but now outdated as a code term. Applications for code compliance include:

• Fire wall separation
• Fire barriers
• Shaft enclosures
• Fire partitions
• Smoke partitions

In high-rise buildings, sliding fire door systems are often the least expensive means of separating the elevator lobby from the remainder of the building and to provide egress doors as required by code. Sliding fire doors can maximize the opening into the elevator lobby and minimize any design constraints associated with accommodating doors swinging into the elevator lobby or encroaching on exit corridors.

Sliding door systems are found in Marriott, Hyatt, Walt Disney World, Ritz Carlton, and Hilton hotels. They also provide for open and easy accessibility to the gaming floors in many Las Vegas hotels. Caesar’s Palace, for instance, has a concealed specially engineered 32-foot-7-inch-high 1.5-hour sliding fire door separating the multimillion-dollar Roman Forum shopping mall from the casino’s main gaming area (noting the heavy track system and proposed construction modifications, UL issued an oversized special door certificate).

Sliding doors deliver spaciousness and open access in megaplexes, as well as provide fire separation walls required to compartmentalize the area. Some sliding fire door systems in shopping malls and sports facilities reach 100 feet in width when open. At the other end of the spectrum, sliding door assemblies have been used at the entrance of parking garages where there was insufficient height for a typical roll-down fire shutter.

In addition to being fire-code compliant, sliding door systems offer security against break-ins. In one California shopping mall, burglars succeeded in breaking through traditional roll-down gates, but their crowbars failed to dislodge the steel sliding door assembly installed in a fire separation upgrade at the entrance to the mall.

Concealed sliding fire-rated door systems that can also seal off sections to separate occupants are an ideal solution in airports whose business is to move many thousands of travelers quickly. The addition of the International Terminal at Baltimore/Washington International Airport required an area separation between the new and old terminal. RTKL of Baltimore, which provided a package of regionally sensitive graphic materials and a comprehensive set of tenant criteria, protected the wide span openings with a sliding fire door. The door assembly allows an unobstructed flow of airport traffic by remaining in the open position and yet having the capability to automatically close when the building fire alarm system is activated. Sliding fire door systems are also found in Orlando International Airport, Charlotte Douglas, Newark, San Diego, Ronald Reagan Washington International, and many other airports.

Inspired by the Bilbao Guggenheim Museum, the 42,000-square-foot Cerritos Library addition by CWA AIA Inc. of Glendale, California, is a library of the future. With three floors wrapped in a skin of titanium that allows fluid compound curve, the building is the first titanium-clad structure in the United States. It contains 1,200 Internet ports, hundreds of computer workstations, plus a 15,000-gallon saltwater aquarium. A wide span curving sliding fire door system provides invisible protection for the interior stairways. With no floor track, a sliding door system provides invisible vertical separation of the third floor.

Expansions and renovations to historic buildings invariably involve solving code requirements relating to stairwells, staircases, and issues arising from combining the old with the new. Concealed curved sliding fire doors will provide vertical separation, protect staircases, and maintain openness.

Knowing the New Code

During most of the past century, the use of horizontal sliding fire doors was limited. They could not, for instance, be used as the primary means of egress, and, when used to separate internal spaces, they were required to meet stringent fire-resistant requirements. But early models, developed for acoustical purposes, equipped with a two-track folding partition system encasing a dead air space, were also capable of resisting fire.

In 1977, sliding door systems passed two UL tests for door assemblies and were shown to withstand intense temperatures rising to 1,700 degrees Fahrenheit. Later, the National Fire Protection Association (NFPA), which develops, publishes, and disseminates more than 300 consensus codes and standards involving life safety features such as sprinklers and alarms, exits, windows, and doors, permitted the use of sliding fire doors as a means of egress in selected applications. These included protecting elevator lobbies in buildings where the occupant loads were less than 50 and as fire and smoke barriers in health-care facilities. Published in the 1988 edition of the Life Safety Code, the new standards were adopted by the then existing three regional model building groups. These were the:

1. Southern Building Code Congress International, which covered the southern and Gulf states and produced the Standard Building Code
2. Building Officials and Code Administration, which covered the Northeast and Midwest and produced the National Building Code
3. International Conference of Building Officials, which covered California and the West and produced the Uniform Building Code

In 2000, the three groups merged and produced a single national building code, the International Building Code (IBC). At approximately the same time, horizontal sliding doors were approved as an acceptable means of egress in all applications, regardless of occupancy loads, except for applications known as Category H applying to storage of flammable and toxic materials. The NFPA adopted the changes so that, in effect, both the IBC and NFPA contain the same requirements regarding sliding fire doors.

The IBC Code Section 1010.1.2 states, “Egress doors shall be side hinged swinging.” But exception #6 (in the 2015 version) reads, “In other than Group H occupancies, special-purpose horizontal sliding, accordion, or folding door assemblies complying with Section 1010.1.4.3.”

The 2015 NFPA 101 Life Safety Code accredited by the American National Standards Institute (ANSI) states:

7.2.1.14 Special-Purpose Horizontally Sliding Accordion or Folding Door Assemblies shall be permitted in means of egress, provided that all of the following criteria are met:

1. The door is readily operable from either side without special knowledge or effort.
2. The force that, when applied to the operating device in the direction of egress, is required to operate the door is not more than 67 N (Newton) (15 lbf [pound force]).
3. The force required to operate the door in the direction of door travel is not more than 133 N (30 lbf) to set the door in motion and is not more than 67 N (15 lbf) to close the door or open it to the minimum required width.
4. The door is operable using a force of not more than 222 N (50 lbf) when a force of 1100 N (250 lbf) is applied perpendicularly to the door adjacent to the operating device, unless the door is an existing horizontal sliding exit access door serving an area with an occupant load of fewer than 50.
5. The door assembly complies with the fire protection rating, if required, and, where rated, is self-closing or automatic-closing by means of smoke detection in accordance with 7.2.1.8 and is installed in accordance with NFPA 80, Standard for Fire Doors and Other Opening Protectives.

The driving force behind the changes was the recognition that the horizontal accordion-type sliding door is a significant improvement over traditional swinging doors for the evacuation of people and has had a major impact on building safety and design. The general acceptance of Universal Design, which promotes design that is accessible for all regardless of ability or disability, plus the passing of ADA in 1990, further reinforced the acceptance of sliding doors for both fire and egress requirements. “Gaining acceptance for this fire door technology required not only that the products prove to be as effective as swinging doors for both ambulatory and non-ambulatory individuals, but it had to perform better, and this has been proven over four decades,” says Scott Smart, president of Won-Door based in Salt Lake City, Utah.

Unlike traditional vertical rolling assemblies where exposed parts are susceptible to damage caused by material handling equipment or abuse by building occupants, horizontal sliding door systems with completely concealed parts are virtually trouble free. Moreover, sliding door systems equipped with integrated microprocessor technology that continuously monitors all door functions enables the system to automatically reset itself following power bumps or building alarms. An industry-wide survey by FM Global, a leading commercial insurance company, found that nearly 80 percent of all conventional fire doors failed because of improper resetting or obstacles that prevented the door from closing.

Conclusion

Clearly, horizontal sliding self-closing door assemblies are an effective way to fulfill means-of-egress and life-safety requirements across the spectrum of building types. They are also a catalyst for architectural versatility, as more design professionals appreciate the possibilities resulting from revised codes. Smart adds, “This technology is unique in its ability to adapt to almost any opening size or configuration while still meeting the strict fire and egress requirements, and that is truly architectural freedom.”

Won-Door™ FireGuard products are specified worldwide in all types of commercial construction projects. Won-Door Corporation makes the most technologically advanced horizontal sliding fire door products in the building construction industry. The FireGuard system is fire-rated for up to 3 hours and meets all egress requirements found in the IBC and NFPA. www.wondoor.com