Horizontal Sliding Fire Doors: Catalyst for Architectural Versatility  

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 twentieth century codes have not always accepted 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 U.S. 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.

Curved sliding fire doors protect multi-story stairways and eliminate the need for costly smoke removal systems. Photo courtesy of John Durant

 

From the $2.4 billion Venetian Macao, anchor luxury hotel on the Cotai strip under construction 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 moving people through an unobstructed exiting system of a building quickly. 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 customdesigned 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 the new 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 5.5 pounds per sq ft. Panels are 4-1/2 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. Each folding door panel is 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, one hour, one-and-a-half hours and three 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) Code, which requires speed of not less than six inches per second and not to exceed 24 inches per second. The typical rate of opening and closing is between eight and nine inches per second. At this rate of speed a clear opening width of 80 or 90 inches can be created in ten 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 three to five pounds of pressure on the fire exit hardware will 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 multi-story buildings during fire emergencies. Most manufacturers set the force to open at five 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.

Without a fire-rated sliding door system protecting the exit in this school, the corridor would require a wall and swinging doors, which could cause congestion in an emergency. (Top) Photo courtesy Mark Thomas Productions Ltd. , (Bottom) Illustration by Gary Rackcliff

 

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 fifty 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 sq ft 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 over 6,600 sq ft of sliding doors as invisible fire breaks that allow people to move freely between the exhibition spaces.

Unlimited openings in this museum were possible through the use of sliding fire-rated doors. Photo courtesy of Sutton Photography

 

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 multi-level 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-ft 7-in high 1-1/2-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 providing 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.

Typical Features of Horizontal Sliding Door System

1. Exiting hardware Exiting hardware can be configured and placed where appropriate. This includes accommodation for persons with disabilities. It is purposely designed to provide a sharp contrast from the door's surface and includes both graphic images and bold lettering. Extensive time and motion studies have demonstrated that the hardware is easily recognizable and operable without any type of special knowledge or effort. 2. Leading edge obstruction detector The door will stop upon contact with an obstacle, pause, then re-seek the closed position. 3. Leadpost (not pictured) Doors can be prevented from closing and caused to re-open a preset distance by applying light pressure to the leadpost. 4. Single- or bi-parting doors (not pictured) A single door slides across the opening into a recessed jamb located on the opposite wall. The spanning of larger openings is possible by using the bi-parting configuration. The storage space is then divided on each side of the opening. 5. Pocket cover door (not pictured) Pocket cover doors can be designed to blend with any interior finishes. Pocket doors stay closed with a simple magnetic latch. 6. Track and trolley system The two-track system allows the door to accommodate wide span openings. Curved configurations are also possible. Typically the tracks are installed 3-1/4 inches above the ceiling line. 7. Thermal lockout feature Ambient temperature at the door is monitored and the operating device is automatically disabled if the environment becomes untenable. 8. Microprocessor monitoring A control unit located in the door's storage pocket provides continuous monitoring of door status. 9. Power supply Sliding door systems employ a completely electronically supervised system utilizing solid-state circuitry as well as a backup DC power supply. 10. Floor gasket and fire liner A tight-fitting floor gasket and insulated liner provide an impenetrable barrier against the spread of smoke and flames. 11. Modular design Modular design provides for in-place reparability using basic tools.

Photos courtesy of Alan Wood

 

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.

Sliding doors keep airport corridors open for moving travelers but will separate areas in an emergency. Photo courtesy of Michael Dersin Photography

Concealed sliding fire-rated door systems that can also seal off sections to separate occupants are an ideal solution in airports whose business is moving 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.

Invisibly hidden in pocket doors when open, a curved sliding door offers fire protection for the interior stairway of this library. Photo courtesy of Promotional Design Associates

 

Inspired by the Bilbao Guggenheim Museum, the 42,000 sq ft Cerritos Library addition by CWA AIA, Inc. of Glendale, CA, 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 U.S.? 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.

MJSA Architects of Salt Lake City, UT, built a semi-circular clerestory to join the renovated 1892 historic Provo City Library, Provo, UT, to a large modern library addition. Since the aggregate square footage exceeded the allowable area defined in the current code, a 2-hour fire barrier was required to separate a large portion of the historic renovation. A horizontal sliding fire door assembly was installed at the junction of one end of the clerestory. "We couldn't have had such a wide span opening," says Christiane Phillips, AIA, who was involved with the project. "We would have had to put in two sets of side hinged swing doors plus some kind of a fixed wall."

Interior atria design with large openings that allow interior spaces to receive daylight, presents a special challenge for health care facilities because code requirements require a 2-hour fire rated separation between floors. The Jewish Home for the Aged in San Francisco, known for investing in environmental design research for its interiors and gardens in order to enhance residents' lives, is an example of complying with code requirements while achieving a rare trio of daylight-filled linked atria.

Designed by RBB Architects of Los Angeles, the three-story, 110,000 sq-ft, 120-bed skilled nursing facility was designed and planned with expanded floor area for the patients, more amenities, and less of an institutional ambiance. A typical residential floor is designed in an intersecting three-circle configuration. Each circle is surrounded by residential rooms and contains a sky lit atrium landscaped with large trees and ornamental plants that are visible from all levels of each circular module. At the intersection of each of these circles is a nurse's station. This floor plan provides a clear view of all entrances to rooms and corridors. A spacious pathway around the atrium leads to the residents' rooms and is designed to invite people to congregate in small groups for social interaction, while still being within view of the nurses' station.

In order to meet 2-hour fire code requirements, RBB specified horizontal sliding doors on each floor at every opening inside the atria that, when closed, would comply with fire code requirements for fire separation between floors. Sliding doors also complied with egress and access needs. "We did not want motel-like corridors where people were separated and there is no connection from floor to floor," says Deneys Purcell, President, RBB. "We wanted to replicate a little courtyard where people could see their neighbor downstairs and have a sense of overall community." Without firerated horizontal sliding doors, he adds, the firm could not have used the atria design and they would have been forced to separate each floor "like a hotel or motel."

Without concealed 2-hour fire-rated sliding doors to separate floors, residents in this senior adults home would not be able to look inside the atrium. Photo courtesy of Won-Door Products

 

Providing egress in retail venues can be a challenge, particularly in high volume turnover stores where stock is stored on the perimeter. At a major retailer, stockroom size is minimized so that the majority of floor space can be devoted to the retail sales floor. Shipments arrive daily and are staged around the perimeter. This configuration presents problems if customers and employees need to leave the building quickly in a fire emergency. Building codes state that the number of exits, travel distance between exits and exit spacing must be based on the square footage and occupancy loads of the building. To meet these requirements, it was necessary that the doors leading from the retail sales space to the stockroom be used as a means of egress ? requiring passage through different types of occupancies. In addition, these exiting corridors needed to be separated from their adjoining areas, often requiring a large span fire-rated barrier. Traditional fire doors would have limited the size of opening, required multiple sets of doors and increased maintenance costs.

Instead, sliding fire door systems could be used to separate existing corridors from the stockroom. They had the advantage when open, of allowing unobstructed access to all areas of the loading docks, stockroom and retail space. They also met code requirements for use as a means of egress without occupant load limitations. Specifying sliding door systems can be accomplished at a price comparable to or less than traditional swinging fire door assemblies. Prices are not competitive, however, for assemblies fitting small openings.

In an emergency, sliding doors create corridors from retail spaces through the stockrooms so that shoppers and employees can safely exit. Image courtesy of Steve Stankiewicz

Knowing the New Codes

During most of the last 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 healthcare 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 Southern Building Code Congress International that covered the southern and Gulf states and produced the Standard Building code; the Building Officials and Code Administration, that covered the Northeast and Midwest and produced the National Building Code; and the International Conference of Building Officials, that 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 1008.1.2 states that "Egress doors shall be side hinged swinging," but exception #6 (in the 2006 version) reads: "In other than Group H occupancies, horizontal sliding doors complying with Section 1008.1.3.3 are permitted in a means of egress."

The NFPA 5000®, Building Construction and Safety Code® accredited by the American National Standards Institute (ANSI), states:

7.2.1.14 Horizontal-Sliding Doors. Horizontal-sliding doors shall be permitted in means of egress, provided that 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.

6. The door shall be power operated and shall be capable of being operated manually in the event of power failure.

 

The driving force behind the changes was the recognition that the horizontal accordion type sliding door is a significant improvement over the traditional swinging door for the evacuation of people. 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. "In my opinion, mainstreaming the provisions for the use of sliding doors as a means of egress in all of the U.S. model codes represents the complete legitimization of this technology," says Tim Welch, vice president of business development at Won-Door, based in Salt Lake City, UT.

 

Tests and field use have shown that horizontal sliding fire door systems are highly reliable. "This is state of the art fire protection equipment with three decades of proven reliability," adds Welch. 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 which prevented the door from closing.

Clearly, horizontal sliding self-closing door assembles are an effective means for meeting 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.

Won-Doorâ„¢ products are routinely specified in major design projects around the world. At Won-Doorâ„¢ we pride ourselves in making the most technologically advanced products in the building construction industry, but we recognize that our strength is found in the unique level of commitment and dedication of our people. We hope you will let us show you how the use of Won-Doorâ„¢ products can make a difference on your next project. www.wondoor.com