ResourcesContinuing Education

Designing for Security


by Barbara A. Nadel, AIA


This month’s installment of the ARCHITECTURAL RECORD / AIA Continuing Education series contains valuable lessons from the federal government’s approach to building security. Use the following learning objectives to focus your study. After reading the article, complete the questions and check your answers. AIA members may fill in the self-report form and send it in for two AIA Learning Units. —Mark Scher, AIA Director Distance Learning

Learning Objective:
After reading this article, you will be able to:

1. Summarize the government's five levels of building security classification.

2. Explain the GSA’s four areas of corrective action for enhancing building security.

3. Describe general elements of secure design for buildings with regard to perimeter, entry, interior, and security systems planning; glazing; parking and access; and building systems strategy.

The 1990s marked a flashpoint for architectural design and safety in the workplace. The February 1993 bombing of the World Trade Center in New York City obliterated the American public's sense of immunity to large-scale domestic- and international-terrorist attacks. The April 1995 bombing of the Alfred P. Murrah Federal Office Building in Oklahoma City and the still-unsolved 1996 bombing at Atlanta's Olympic Centennial Park heightened concerns about security in public buildings and spaces. These national tragedies permanently changed the way government and corporate clients locate, plan, and design public facilities. As a result, security will continue to be an essential criterion for planning buildings for the foreseeable future.

Security-design strategies can most effectively minimize the loss of life and property through integrated use of technology, operational policies, and facility planning. Understanding the exact nature of what may threaten a building is important, especially in the early project development phases. From site selection and materials specification to structural systems, every design decision may someday be crucial to saving lives and preventing damage as a result of an attack, accidental explosion, or natural disaster.

Threats, targets, and terrorism
Security design anticipates targets, potential threats, and means of attack. The goals are to protect people, buildings, products, services, equipment, proprietary information, and often possessions and priceless artwork. Most clients prefer not to publicize the threats they receive, unless danger is imminent. Similarly, clients are reluctant to discuss preventive security measures put in place. As a result, the public rarely hears about potential threats unless a disaster occurs. The biggest danger, suggests a former FBI official, may come from loners or small antigovernment groups who can access intelligence information and floor plans on the Internet.

Public buildings are vulnerable to threats, exterior attacks, ballistic missiles, and vehicle bombs--the last being the most destructive and easiest to create. Chemical and biological threats are a growing concern, particularly after the poisonous serin gas attack in the Tokyo subway. Other threats include civil disobedience, mob or individual acts of violence, package bombs, or unforeseeable events such as fires, earthquakes, and gas-line ruptures. Given so many possibilities, security experts admit they cannot predict or prevent all possible scenarios, but they can recommend reasonable and prudent precautions.

The bombing of the Murrah building--which left 169 dead, 518 injured, and $100 million in damages--prompted a comprehensive review of security measures for all federal buildings. At the time of the explosion, no security standards existed for federal buildings, says Anthony DiGregorio, senior technical advisor at Applied Research Asso-ciates, an Alexandria, Virginia, consulting firm specializing in industrial security and protection. Immediately after the bombing, the U.S. Department of Justice, under presidential directive, developed federal standards on the ``hardening'' of buildings to explosives and other potential domestic threats based on the findings of the June 1995 report ``Vulnerability Assessment of Federal Facilities,'' known simply as ``The Marshals Report.'' As the principal owner or landlord of the 1,300 federal buildings investigated, the General Services Administration (GSA) was designated to coordinate security standards and cost assessments.

A multidisciplinary team of security experts classified federal buildings into five categories, or levels, based on facility size in square feet, number of employees, and volume of public access. After continued refinement of the draft report through 1997, the GSA Security Design Criteria were accepted as the guidelines for ensuring public safety at all federal buildings. The criteria will likely remain in draft form, because an act of Congress is required to make any changes.

Generally, the larger the facility, the more employees, and the larger the degree of public access, the greater the need for security. Most federal facilities fall into one of the first four levels of safety requirements, from level one, the lowest, to level four. Facilities critical to national security, such as the Pentagon, have the highest possible security classification, level five. A level-one facility, for example, might not require an entry control system, while a level-four facility would require electronic controls with closed-circuit television (CCTV). A small facility with just a few employees and a low volume of public contact may not need much in the way of security, but some measures are required, such as lighting with emergency power backup.

Federal law enforcement agencies often have their own security needs, and the GSA cooperates with them in meeting these requirements. For example, at the request of the FBI, the GSA directed that the bureau's new 306,000-square-foot field office in Washington, D.C., receive facade and structural improvements to provide additional blast protection at a cost of $5.9 million for construction and $1 million for design fees. The total cost for the building was $93.4 million, according to the GSA.

Recommendations for improved security
The GSA's recommendations apply to levels one through four for building design and construction, security systems, operations, and equipment. Design and engineering requirements fall into four general categories of corrective action at perimeters, entries, interiors, and the security planning of the overall facility.

Perimeter security is essential to prevent either a moving or stationary truck bomb attack. The next generation of new federal courthouses, now under design or construction, will integrate landscaping, site planning, and parking controls with more visible security measures, including CCTV monitoring, lighting with emergency backup, and physical barriers or bollards. Standoff distance is a term used to describe the limiting of vehicular access through street setbacks.

Entry security is critical at federal courthouses and other facilities containing criminal justice agencies, although individuals may view any building that is a symbol of authority as a target. Thus, the location and design of main entrances, loading docks, mail rooms, and utility mains is of particular concern. At main entrance lobbies, magnetometers, such as those used at airports, and electronic detection devices can identify deadly weapons and explosives.

In recent years, the threat of mail bombs has prompted greater security in mail rooms and more thorough package screening. Loading docks and shipping and receiving areas are also potential targets for larger package explosives or vehicle bombs and are places where an intruder may try to illegally enter a facility. To minimize potential damage, delivery areas should not be located near mechanical areas or underground. Other entry precautions include installing intrusion-detection systems and upgrading current life-safety standards. Many buildings--even in the private sector--now use sign-in procedures for delivery people and packages while limiting their access with CCTV entry controls, secure access to utility mains, and heavy-duty locks at higher-risk facilities.

Interior security addresses design and construction materials. Street-level retail spaces in government buildings are also carefully evaluated. At the new Ronald Reagan Federal Building in Washington D.C., shops are located on a lower-level arcade near the public spaces and security increases in upper levels of the building.

Other measures include employee identification; controlling visitor circulation; limiting access to building-control centers; and providing emergency power, computer, and phone lines to critical systems. The GSA also evaluates child-care center locations in federal buildings. Future planning will include the hardening of some day-care centers and site assessments to mitigate potential threats by moving them away from high-risk areas.

Security planning includes assessing the specific risks of the various federal agencies--such as the FBI and the Bureau of Alcohol, Tobacco and Firearms. During site selection and planning, consideration is given to whether these agencies belong in an open, multitenant office building or in their own building, located where dangers are minimal.

Paradoxically, there is a fine line between informing design professionals on planning safety design standards and aiding those seeking to circumvent these measures. For that reason, the GSA divulges information about the design criteria on a need-to-know basis to those involved in federal projects. Some architectural firms contacted to discuss how the security measures apply to federal courthouses in various design stages declined to comment or provide photographs, on the advice of the GSA.

The GSA Security Design Criteria
According to Wade Belcher, architect in charge of the security design standards at the GSA Public Building Service in Washington, D.C., ``few buildings have been completed with designs based on the security criteria. Many buildings have had components from the criteria included through retrofit projects; however, most have chosen not to disclose what the elements are.'' Nevertheless, private-sector security experts, architects who specialize in justice facilities, and structural engineers specializing in blast design, who are familiar with the GSA security criteria, can offer insight into security design measures applicable to many building types.

The main goal of the GSA security criteria is to save lives and prevent injury. Secondary goals are to protect federal buildings and assets. The security criteria provide a performance-based approach to various building systems and components, from window glazing to structural systems. In the event of a major terrorist or criminal act, structural, mechanical, electrical, and life-safety criteria are aimed at facilitating safe evacuation and rescue.

These criteria address security concerns while considering cost parameters and acknowledging an acceptance of risk. Officials recognize that federal buildings should not be fortresses or bomb shelters, but rather buildings that are open, accessible, and well woven into the community fabric.

A security-risk assessment is required at the early stage of each federal project. Risk factors may be as diverse as a building's symbolic importance if it is a highly visible landmark or its function if it is considered vital to national interests (such as a national monument, an air traffic control center, or the White House, for example). Other factors to be assessed include the overall effects of an attack, including death and injury, property damage, and workplace interruptions. Costs associated with repairs and replacement are also considered. Designs should allow for the ability to increase security in response to a heightened or temporary threat, such as at a federal courthouse during a high-profile trial. More costly or inconvenient measures, such as prohibiting parking, may be implemented as needed.

Facility planning should follow a tiered defense system, with zones of security starting at the building perimeter and decreasing toward its core. The tiers include the standoff distance in front of the building, building exterior walls, the screening-and-access control area, and safe interior areas for valuable assets. Each building system should support an interdisciplinary approach to mitigate risk and reduce casualties, property damage, and loss of critical functions. Security should be considered in all decisions, from trash receptacle placement to the design of redundant electrical systems. Critical functions and life-safety systems should be located toward the inside of the building, away from the exterior, where they are more vulnerable to explosions.

Parking within the facility should be access-controlled, and surface parking should be controlled with appropriate perimeter barriers; handicap accessibility must be maintained. Magnetometers and X-ray equipment should be integrated into the entrance lobbies. Egress lighting should have emergency power backup. Emergency power units should not be co-located with primary power units, as they were at the World Trade Center, where a single underground explosion disabled both power sources.

Physical barriers--bollards, planters, street furniture--should be considered as a means of lending a building added protection where only a minimal setback from the street is available. A given facility's individual security requirements should be considered when deciding whether to limit direct pedestrian and vehicular access to the building. It is essential to evaluate shipping and receiving areas for potential location in a remote area of the facility. The selection of glazing and fenestration materials should be evaluated based on their performance when subjected to lateral forces.

Site and design issues
The creative use of site planning, perimeter definition, sight lines, and lighting can eliminate the need for awkward engineering solutions that might result in less-than-pleasing buildings.``The challenge to architects is to provide an inviting community environment and deal with physical security. These are not contradictory and can enhance one another,'' says Ed Feiner, FAIA, chief architect for the GSA. ``Physical imagery is important. The most successful federal buildings are `transparent'--the security elements are in place, but they are not visible to the public.''

Feiner adds, ``The GSA evaluates each potential threat individually. There is no cookbook to solve all problems; every building is different. The security criteria attempt to define how a solution should perform in any given situation, rather than establishing hard-and-fast rules that can't be tailored to specific needs.''

Security planning begins during property and site selection. ``The GSA prefers sites with some breathing room,'' says Feiner. ``Not a buffer zone--that's for a fortress. Historically, small city courthouses are set on a lawn on a hill, to create an icon with a grand civic presence for the public. The GSA wants to achieve that image and derive security benefits at the same time.''

Even in an urban setting, standoff distance is used to address vehicular traffic and reduce the exponential effect of a car bomb. For example, the new Brooklyn Federal Courthouse project included an experimental program to combine art and architecture by inviting artists to work with structural engineers. The goal is to put the best face on necessary security requirements, with less intrusive, visually interesting perimeter security devices, nonstructural elements, and bollards.

Avoid flying glass
The blast at Oklahoma City's Murrah Federal Office Building resulted in many lessons for future construction of federal facilities, especially relating to glazing, life-safety issues, and structural systems, notes Don Porter, AIA, partner at HLW International, in New York City, and project manager for the Brooklyn Federal Courthouse.

Similarly, the explosion at the Khobar Towers, an American military housing compound in Dharan, Saudi Arabia, provided information on how glass shatters during a blast. Window film was scheduled for installation but had not been applied at the time of the explosion. Most of the fatalities in Oklahoma City and Dharan resulted from shards of glass, which flew as far as 100 feet into the building.

The GSA and manufacturers have studied and tested several types of glass, security window film, and other materials under test explosions. Glazing with protective film may be effective in some cases, but blast experts claim that more testing is required to generate conclusive data. ``The data is lacking on how best to protect windows and curtain-wall construction,'' Porter says. ``There is no empirical data on the effects of blasts and no agreement on what works best--glazing, films, and window frames--especially in retrofits. We can't do a 100 percent job on security--then we'd just end up building a bunker--so there are compromises involved.''

Fully tempered glass has some problems with spontaneous failure, but experts say it performs better in a blast environment than float or annealed glass; when shattered, it produces small cube-shaped projectiles with significantly higher breaking strength than pieces of float glass. Laminated glass, which consists of a layer of film laminated between two pieces of glass, tends to stick to the laminating film and stay in window frames when broken. This reduces the number and velocity of flying fragments. During failure, float glass creates large, sharp-edged shards resembling knives and daggers, experts say. For window assemblies to stay in place, the glazing, mullions, and anchors must be able to resist blast pressures enough to transfer loads to the adjacent structure.

Courthouse design
Courthouse designers have been addressing issues of enhanced security for state and county projects for a while now. ``The federal guidelines raise the requirements to another level. There is no total answer to the best approach,'' says Don Dwore, AIA, principal and director of the justice facility group at Spillis Candela & Partners, in Coral Gables, Florida. Typically, security comprises 4 to 5 percent of a courthouse project's construction costs, Dwore estimates, and perhaps 3 percent or less for county projects. At the $22 million Charlotte County Courthouse in Pensacola, Florida, approximately $400,000 was spent on security measures.

``Judges want secure buildings, parking, and a secure path to their chambers. They don't want to be shot and killed on the way to work,'' Dwore observes. ``When assessing property, street setbacks are important. Raising courthouse functions well above street level, use of wide stairs, ramps, hardened building elements, bollards, and landscaping can prevent vehicles from causing further damage to secure areas. Large-caliper trees on site can keep vehicles at a safe remove from the building.''

Life-safety systems
Security planning is now integral to building and life-safety systems. Experts recommend that mechanical systems include gas detectors and the capability to keep biohazards out of fresh-air intakes, especially at research and lab buildings.These should be located where unauthorized access will be minimized as well.

Fire sprinklers should not branch off from the main water-supply line at a point where they would be vulnerable to failure if there were an accident. Similarly, water mains and pumps should be plumbed so that if a break occurs in the main, there is an alternate way to get water to the pumps. Building-utility areas must be secured by controlled access. Fire stairs and areas of refuge and escape should not empty into main lobbies or loading docks because these are areas of high potential risk for an explosion, and evacuating people through them could cause injuries and panic. Exit stairs are much more easily rerouted during the conceptual design phases than later on.

Security-system lines, telecommunications, and electrical power should be routed separately rather than run through a single duct. Main electrical feeds should not enter buildings at potentially vulnerable locations, such as loading docks, receiving areas, and main entrances. Redundant systems, if located remotely, also provide a level of protection. If one system malfunctions, the other can replace it.

Parking garages
The World Trade Center bombing in an underground public parking garage caused several floors to collapse, destroying the chiller plant and the backup emergency generator system. Primary and secondary systems were located side by side, not remotely. ``Public underground parking should not be located near critical building systems, backup generators, or gas meters,'' observes William Daly, managing director of Kroll-O'Gara Company, a New York City security, investigative, and risk-management firm that was a consultant to the Port Authority of New York and New Jersey for the World Trade Center after the disaster. ``Such areas require compartmentalization, and their walls should be strengthened with steel plates to deflect explosions. Locating emergency systems above grade is better to avoid flood damage, but if they should catch on fire on upper floors, extinguishing the flames is very difficult.''

Since the bombing, underground parking has been limited to prescreened tenants. Deliveries must be preauthorized and may be received only at checkpoints from those with identification.

Several new automated-access controls in office buildings reflect new technology, says Daly. Biometrics electronically read the contours of hands for identification. Retina scanning, fingerprinting, and proximity-card access systems are user-friendly methods to screen pedestrian traffic.

Blast-resistant design
Blast design is a relatively new area for commercial and civilian buildings, and there are several points of view on the subject. Some federal agencies want to enhance vulnerable portions of their building by localizing blast resistance, or hardening, says David Kossover, P.E., a New York City structural engineer and blast expert. In contrast, the British don't recommend hardening their civilian buildings but assume there will be a certain amount of damage. They concentrate on mitigating partial or total building collapse and on improving the blast resistance of the exterior glazing. Others claim that reinforced-concrete and steel buildings with well-detailed connections often withstand pressures and vibrations from explosions and do not sustain extensive permanent damage. They also admit it is not possible to design a bombproof building that will survive undamaged and guarantee few injuries. Instead, limiting damage and human injury is best achieved through good design, not necessarily through localized blast-design techniques. This debate will most likely continue in the years ahead.

Features that enhance buildings may also make them more vulnerable to attack. Windows and atria provide openness and daylight but also contradict blast-mitigation objectives, asserts engineer Tod Rittenhouse, blast expert and principal of Weidlinger Associates, a New York City consulting engineering firm. Blast-mitigation strategies permit significant localized damage while preventing catastrophic collapse. Casualties immediately near a blast may be unavoidable, but by preventing progressive collapse, further fatalities may be reduced.

Seismic design does not apply to blast resistance, because earthquakes and explosions affect buildings differently. Blasts usually affect a relatively small geographic area around a building's perimeter, while earthquakes move the entire building. When a building is hit by a bomb, damage generally occurs to its skin, floors, and interior walls. These areas are not designed to transfer blast loads to a building's frame, so they may tear away, leaving the structural frame intact. Even though a structure may not be damaged by a seismic event, in a blast, permanent deformation of columns and girders (see sidebar, page 146) may occur in areas near an explosion.

What lies ahead?
The GSA's current enthusiasm for the design-build method of project delivery raises concerns that some aspects of security design will be diluted during budget reviews. ``As government agencies move from traditional design-bid-build to alternatives like design-build, it will be interesting to see how security criteria will be value-engineered and applied,'' says John Sporidis, senior vice president of HDR Architecture, in Alexandria, Virginia. ``When projects go the design-build-developer route, we must pay attention to ensure that the integrity of the design is not compromised and nothing is lost.''

By all accounts, Americans haven't seen the last terrorist attack on public- or private-sector buildings. Clients--and the public--will continue to demand comprehensive yet unobtrusive security responses from the design and construction industries. It is also essential that research continue to find the most appropriate building materials that can withstand a host of attacks, accidents, and disasters. The challenge ahead is to seamlessly integrate life-safety and security measures with aesthetic building design. Security need not be incompatible with good design--and the use of prudent precautionary measures may save countless lives and millions upon millions of dollars in damages.


  1. Give an overview of the GSA Security Design Criteria derived from the Marshals Report.

  2. Explain the four general categories for facility design and engineering security requirements.

  3. Describe what rudimentary security assessments should be made early in a public project.

  4. Describe the security lessons that were learned from the damage and problems experienced in the World Trade Center bombing.

  5. List two types of glass that reduce the number and velocity of flying fragments in a bomb blast and discuss what is needed for strong window assemblies.

  6. Describe two general apporaches to blast-resistant design and a three-pronged approach for protecting security, telecommunications, and electrical systems.