NEW DIMENSIONS IN HIGH-RISE CONSTRUCTION: MULTIFLOOR CORRIDOR DESIGN
STRATEGY & TACTICS
The increase in residential high-rise building construction in this country, particularly the high-rise condominium, has led to unique, innovative architectural designs. These innovations have drawn the attention of developers who wish not only to make their buildings more attractive but to utilize space to the fullest as well. Unfortunately, life safety rarely takes the front seat in the builders’ drive to construct more marketable and profitable living spaces; worse, simply complying with building codes and standards does not necessarily ensure adequate fire protection. Therefore, it’s incumbent upon local fire departments to make certain that life safety is the top priority in building design and to become intimately aware of new designs that demand unusual strategy and tactics.
THE MARK OF A HIGH-RISE
Although different fire departments may develop their own operational definitions of high-rise, most definitions include four common characteristics:
- They contain portions that are beyond the reach of fire service aerial equipment.
- They pose significant dangers of vertical and horizontal fire spread.
- The time it takes to evacuate occupants completely is generally great.
- They contain features not common to other structures.
These four characteristics contribute to the difficulties firefighters encounter when responding to high-rise fires in general. Let’s focus on a relatively new type of residential high-rise that demands our attention. This highrise contains features rarely encountered by the fire service, the most significant of these being its corridor design.
NOT TO SCALE
The apartments are numbered as followed: 3-2A; 3-3A; 3-4A; 3-2B; 3-3B; 3-4B; etc. The first digit denotes the corridor floor, the second digit is the actual floor upon which the apartment is situated, and the letter identifies the specific apartment. Note that all similarly lettered apartments are stacked on top of one another.
THREE FLOORS, ONE HALLWAY
In an effort to maximize living space, three floors of units share one corridor. The corridors are located on every third floor of the building. Units on the floors above and below the corridor floor are accessed by individual scissor staircases located behind the unit doors along that corridor; apartments located on the corridor floor are the same as those of a traditionally designed building. There are three times as many individual apartment doors on the service floor corridor as compared with corridors in buildings of traditional design; twothirds of these doors lead to units either one floor above or below the main corridor floor.
FIRE SAFETY RAMIFICATIONS
Corridor traffic. With triple the number of apartment doors per corridor—and, given the general length of these types of buildings (approximately 300 feet), that number is considerable-corridor traffic during evacuation is also tripled. The need for an orderly, well-conceived evacuation plan is imperative.
Corridor location with respect to the building. In general, units are located at the front of the structure to provide scenic views. Corridors are located at the rear, where swimming pools, tennis courts, or other obstructions can prohibit access by fire department aerial equipment.
Distance between occupancies and exits. In this type of construction design, occupants on the floors above and below the corridor must travel through their apartments, up or down the stairs, and then through a corridor to reach an exit to the street. (While automatic sprinkler systems are not a substitute for adequate and safe exits, they are recognized in a number of ways by the NFPA 101 Life Safety Code to permit greater travel distances to exits.)
Scissor stairs. Access to the corridor serving the occupancies in this type of construction is usually scissor stairs—two separate staircases enclosed in one stairwell that are accessible by each floor. There are two types of scissor stairs: In the first, the doors for a particular stairs are stacked one above the other served by half-return stairs; in the second, the access door position alternates location at each floor and is served by straight-run stairs. For example, on a given floor the left door would access staircase A while the right door would access staircase B; on the floors above and below this location the door markings and locations are reversed.
There are difficulties associated with straight-run scissor staircase designs:
- Only one of the two staircases contains standpipes. Even though adequate markings are required to identify each standpipe, if personnel enter the wrong stairwell they must relocate to the other. This could mean returning to a floor located at a safe distance below the fire floor and then entering the proper staircase; otherwise firefighters face the possibility of entering the standpipe stairwell on the fire floor. In any case, relocation is a time waster.
- Occupants should be encouraged to evacuate via the staircase without standpipes to avoid smoke and heat in the staircase with doors open for firefighting operations; to avoid stairway congestion; and to avoid interfering with fire department operations. However, since the incident commander must give evacuation priority over fire attack, occupants may be using both staircases, slowing down operations. After evacuation is completed, both stairs may be used for firefighting operations.
Apartment layout. Each individual apartment warrants special consideration by fire service personnel. We know that one of the most significant life safety factors in high-rise buildings is the protection of vertical openings, since fire’s natural tendency is to rise vertically. Experience tells us that the greatest life hazard results from a fire that is located below occupants’ means of egress. Similarly, fires in high-rise buildings may result in smoke and fire spread into enclosed exits prior to evacuation. Therefore, construction design must offset these tendencies to the maximum practical extent.
Fires in apartments one level below the corridor floor pose the most serious problem to inhabitants and firefighters alike. Evacuation must be carried out by way of the staircase within the unit. Unfortunately, smoke and heat can be expected to travel into this staircase. This is by far the most serious fire safety ramification in this high-rise design. Should sprinkler operation be ineffective in one of these lower apartments, firefighters would be hard-pressed to enter the apartment to carry out rescue and firefighting operations. Fires in this location compare with fighting a fire in an occupied cellar by entering the “chimney”—the narrow access stair.
In the case of fire occurring in the floor above the corridor, upper-level apartments would be somewhat easier to evacuate since the exit is lower than the apartment floor. Firefighters would have an easier time gaining entry into the apartment since smoke and heat should not be rising to and mushrooming at the entry level.
Evacuation for the apartments on the corridor level would be carried out as per usual SOPs. But keep in mind there are unusual exposure problems above and below this occupancy.
Ventilation. Because a number of apartments are located below the floor level of each corridor, smoke and heat travel would be accelerated throughout the hallway should one of these units be involved. Ventilation is difficult for the lower apartments because firefighters will be faced with heat and smoke banking down at the door. As with most high-rise fires, prompt horizontal ventilation is mandatory. This must be done from above, below, adjacent, or outside. This tactic could be easily effected by use of an aerial ladder, provided that the involved apartment is within reach of it.
SOP changes. Fire department standard operating procedures must be altered to suit this type of construction. For example, the generally accepted SOP requiring that firefighters exit the elevator two floors below the fire is not always possible because elevators are on every third floor. In buildings as complicated as these it’s recommended to abandon all elevator use until the exact location of fire is ascertained and the corridor is protected by at least one operating handline.
Size-up. The time required for initial size-up depends on which floor firefighters are instructed to leave the elevator, if the elevator is used at all. As many as three floors could be sized up quickly via the main corridors. Subsequent firefighting operations likewise could be initiated sooner, as they too could be staged from one floor. Of course, this practice would be neither safe nor practical if heavy smoke conditions were found on the corridor floor. On the other hand, if the staging area is established three floors below the fire hallway, delays in size-up and firefighting evolutions would occur; however, this staging area location would also result in safer firefighting operations, as the firefighters would be farther away from the actual fire.
Standpipes. Standpipe operations also are affected by this construction design. Only one standpipe per stairway can be employed for a fire involving any of the three floors served by a particular common corridor. As a result, lines would have to be wyed off from this one standpipe. This would both slow up and complicate firefighting operations. In addition, greater hose lengths would be necessary due to in-unit staircase distances. In most cases, five to seven lengths of hose will be required to reach the seat of the fire. Standpipes also are located at the midpoint of the common corridors. However, this practice is dangerous and dependent on the lack of positive variables such as heavy smoke and heat conditions in the corridor and the controllability of evacuation patterns of a large number of occupants.
Extension control. Controlling fire extension here would be easier than in traditionally designed high-rise buildings. Specifically, continued sizeup operations during the fire could normally be carried out simultaneously for the floor above and below the fire floor from one location. Internal horizontal and vertical fire spread is also limited because of compartmentation.
Here are some suggestions for fire service personnel who are preplanning for a building of this type:
- Make certain that staircase doors on each floor are adequately marked to indicate the direction of the apartment that they serve.
- Have a knowledge of individual apartment layouts to facilitate firefighting operations, particularly rescue and ventilation.
- Have an SOP for elevator use as well as specific responsibilities for engine, ladder, and rescue company personnel.
- Preplan apparatus position with emphasis on exterior horizontal ventilation and alternate entry.
- Locate the command post close to the incident but far enough away to ensure personnel safety.
- Be well-versed in practical standpipe operations and useful alternate procedures.
A greater knowledge of each building with respect to fire safety and firefighting operations must become an important part of every local department’s routine. This responsibility rests on our shoulders and will continue to do so. It is our task to see that safe living accommodations become the rule and not the exception.
