Making Safer Structures: the Effects of 9-11 on Today’s New Building Codes

Three and a half years after 9-11, building codes are only just starting to reflect lessons learned from the World Trade Center (WTC) collapse.

More movement is likely, however, as further information is gathered about the design elements that did not perform as expected or that hindered rescue and evacuation efforts. The following overview looks at the progress made since 9-11 and at how future building designs are likely to evolve to meet the terrorist threat.

Ground Zero

While few cities have amended their building or life-safety codes as a direct consequence of 9-11 (due primarily to the slow nature of data gathering and analysis and the lack of pressure thus far for new building codes), that go-slow attitude is not universal. As the epicenter of the 9-11 attacks, New York City was profoundly affected, and developers there have been proactive.

For example, Silverstein Properties, which owns the World Trade Center site, “is very interested in going well beyond building codes,” says Carl Galioto, a partner at the architecture, engineering, and urban-design firm Skidmore, Owings & Merrill and member of the New York building code commission. “They’ve been an active leader and partner in developing new ideas.”

Consider the new Seven WTC building. According to Galioto, it was designed with a “robust structure” to protect against progressive collapse, a situation in which local failure of a primary structural component leads to the collapse of adjoining members. This measure addresses the fact that fires in the Twin Towers damaged vertical support members, leading to the buildings’ collapse.

In addition, stairs and elevators at Seven WTC are fully encased in a reinforced concrete core. This reflects FEMA’s finding that the plasterboard that was providing fire resistance to the stairways at the Twin Towers was knocked off by the impact of the jets, rendering it useless and possibly hastening the buildings’ collapse. Seven WTC also has spray-on fireproofing five times more adhesive than called for by existing standards, says Galioto, as well as a redundant water supply for sprinkler systems.

Another fire-safety feature in Seven WTC is that fire stairs are located at opposite ends of the building. (The FEMA report noted that the suicide pilots on 9-11 were able to slice through two sets of emergency stairs because the stairs were close together.) And at 66 inches, stair width goes well beyond code.

Voluntary widening of fire stairs in other buildings is an item under discussion by experts, not just to help with evacuation but to allow space for the counterflow of emergency responders. Many building owners may, however, balk at widening stairs, says architect Barbara Nadel, author of the book Building Security: Handbook for Architectural Planning and Design, because it reduces rentable space.

Moreover, Seven WTC and Freedom Plaza across the street have photoluminescent paint or electroluminescent strips on exit stairs even though they are not yet mandated by code. Freedom Tower will have a third stairwell dedicated to emergency response. And the stairwells in Seven WTC have triple redundancy for stair lights: First, there is emergency lighting to back up regular lighting; then there is battery power; and, if those fail, the photoluminescent paint is in place.

Galioto’s firm is also studying how and whether it could implement some type of stair pressurization to reduce smoke in the stairwells in the event of an emergency. If the air-pressure level inside stairwells is higher than on the floors, smoke migration through closed doors is reduced, he explains.

Such measures are feasible at the WTC site, but are they cost-effective for other properties? According to Galioto, the overall cost of extra security at Freedom Tower and Seven WTC “will be in the single-digit percentages of construction costs,” not including the dedicated emergency stairwell and the wider stairs. These buildings can serve as an example for other iconic or high-risk buildings beyond Ground Zero, he says.

New York Creates New Codes

While firms like Galioto’s have voluntarily incorporated new life-safety features into their building designs at Ground Zero, the city of New York did not want to rely solely on the goodwill of private industry. To that end, New York City’s Department of Buildings formed its own building code task force, which gathered input from government agencies, design and engineering societies, the construction industry, real estate associations, and other experts. The task force also considered earlier recommendations from FEMA, but it preferred not to wait for this year’s comprehensive report by the National Institute of Standards and Technology on lessons learned from the WTC collapse before taking action.

In February 2003, the task force issued 21 recommendations. For example, the task force proposed a requirement that new commercial high rises have elevators that open onto a “smoke-stop vestibule.” In addition, it suggested that existing buildings be required to have inspections, when spaces are being renovated, to assess existing spray-on fireproofing. The task force further recommended that nonresidential high rises be barred from using open-web steel joists. These structural members, which support floors and ceilings, have too little surface area for adequate spray-on fireproofing to be applied.

These proposals echoed the earlier FEMA report findings about the adequacy of fireproofing at WTC buildings. The FEMA building analysis of the WTC remains had found, for example, that some important structural members in the towers lacked adequate, or any, fireproofing.

New York City has codified most of these recommendations through a local law that came into effect in June 2004. Four of the provisions apply retroactively to existing buildings but allow considerable time for compliance. For example, office buildings that are 100-feet tall or higher must have adequate sprinkler systems throughout the premises, but building owners have until July 1, 2019, to comply. For installation of photoluminescent markings on exit signs and stairs, however, high rises have only until July 1, 2006. They have a year beyond that to install additional signs where the exit path is not clear and to provide a battery or generator as a backup power source for existing illuminated exit signs.

These code changes are lauded by fire-safety experts, though some criticize the lengthy time allotted for compliance. Another concern is that few of the new rules apply to existing buildings.

Code Development in Chicago

New York City has not been the only municipality to take seriously the need for changes after 9-11. Changes to Chicago’s municipal code, reflecting more stringent high-rise-safety requirements, quickly followed 9-11. But the Chicago Department of Buildings code changes focused more on planning and the human factor than on structural building issues.

The Chicago provisions tie fire-safety measures to building height. For example, all office buildings 80 feet or taller must have an emergency evacuation plan in place, but only those 540 feet or taller must file the plan with the city’s office of emergency communications. The tallest buildings, those more than 780 feet, must designate a fire-safety director, deputy fire-safety directors, a building-evacuation supervisor, fire wardens, and an emergency-evacuation team. Slightly shorter buildings, over 540 feet and up to 780 feet, need not have fire wardens. Buildings between 275 feet and 540 feet need only designate a fire-safety director and deputies. These provisions include specific staffing requirements; a building’s fire-safety directors or deputies, for example, must be on site when more than half of the building’s regular occupants are present.

Other elements of a valid evacuation plan include evacuation procedures, the posting of a core floor plan, maintenance of a list of occupants needing evacuation assistance, and regular staff participation in safety drills. Stairwells must also be marked to identify floor number and re-entry locations.

Not all of the Chicago code changes are personnel related, however, and some are driven by events other than 9-11. For example, an ordinance passed after the October 2003 fire at the Cook County Administration Building, which killed six people, prohibits the locking of reentry doors in stairwells. And just days after a December 2004 high-rise fire, the city council voted to make owners of pre-1975 commercial high rises install sprinkler systems (a 1975 provision requires only new buildings to have sprinklers). But the impact of that change is blunted by a 12-year grace period for compliance.

Other Countermeasures

While the focus of code changes and design initiatives has been on hardening buildings against structural damage and facilitating evacuation, some building designers and engineers are addressing protection from chemical, biological, and radiological threats. Countermeasures considered for building design include HVAC systems with nanofilters to reduce the spread of toxic agents and sensor technology for early detection. Scientists at the Georgia Institute of Technology are working on chemical and biological sensors that can be built into ventilation systems. Upon sensing a harmful agent, the sensor could trigger a shutdown of the system.

Designers and engineers are also addressing these threats by designing air conditioning systems and ductwork that are segmented by zones that cover just one or two floors instead of 10 or 20. Central-air systems that serve many floors have shaftways and duct systems that penetrate fire-rated walls, floors, partitions, and ceilings. Extra air systems increase cost, but they also potentially limit the spread of toxic agents or smoke.

Building designers are also adapting their own version of crime prevention through environmental design (CPTED). The CPTED objective is to lay out a new building to facilitate, rather than fight with, security’s access control needs, limit injuries from attacks that do occur, and allow for quick evacuation in an emergency. Ron Couch, Stanley Security Solutions’ chief operating officer for security integration, says that he is educating architectural and engineering groups on designing buildings with these CPTED-related principles in mind to enhance security.

In New York, says Galioto, new buildings are designed with these principles in mind. Architects, designers, and engineers consider occupant evacuation, checkpoints for delivery people, and mailroom sites early in the design phase, he reports. For example, lobbies sometimes must accommodate larger reception desks for package and briefcase screening.

Action Needed Elsewhere

Given that terrorism is still seen as a remote threat for most building owners, calls for better building designs may continue to fall on unreceptive ears in places other than major metropolitan areas like New York and Chicago. But, notes Nadel, companies do understand the threat posed by natural disasters. “If we can get their attention dealing with that, they might deal with some of the terrorism issues.”

© 2005 ASIS International, 1625 Prince Street, Alexandria, VA 22314. Adapted with permission from the March 2005 Security Management Magazine.