Cost Impact of the ISC Security Design Criteria  

by Joseph L. Smith, PSP and Larry M. Bryant, PhD
Applied Research Associates, Inc.



This Resource Page discusses the fundamentals and basics of the cost impact of implementing the security requirements of the Interagency Security Committee (ISC) Security Design Criteria. The General Services Administration (GSA) and the federal government are committed to excellence in the design and development of their sites and buildings. This requires an integrated approach that achieves the highest quality of aesthetics in meeting client and building requirements, while delivering a building that is cost-effective to maintain throughout its useful life. One challenge to the GSA and other federal agencies is to explore the extent to which maintaining high quality in design and construction has been affected by security. See WBDG Balancing Security/Safety and Sustainability Objectives. Specific GSA initiatives affecting capital construction include but are not limited to:

In this Resource Page, the costs associated with necessary security measures are discussed as they relate to standoff distance. Security issues considered herein are those required by application of the Interagency Security Committee (ISC) Security Design Criteria that applies to all new construction and major modernization of federal properties.


Security-related costs arise from ISC requirements that influence the design of structural components and non-structural components. For example, the requirements for consideration of blast threats to the facility impact the design, and thus cost, of the structural frame and façade elements including walls, roof, and windows.

The impact of design explosive threat level on cost is reflected in the increased requirements of structural components, e.g., thicker walls, additional reinforcement, blast-resistant glazing and frames, etc. The two primary blast-related factors that influence the design of a structural component are the design threat magnitude (e.g., lbs TNT) and the distance between the potential explosion and the structural component, i.e., the standoff. Note that standoff is the distance to the structure from a defended perimeter, i.e., the closest distance to the design threat.

An increase in explosive weight or a decrease in standoff generally increases structural requirements. Since the ISC Security Criteria impose the design explosive weight magnitude for each level of protection, the building design is influenced by the amount of standoff available. For the defined threat level in the criteria for a particular facility, the designer must balance the effect of available standoff by incorporating blast-resistant design and/or hazard mitigation measures.

The effects of standoff on various structural and non-structural components are illustrated in Fig. 1. This figure generally illustrates, at no particular scale, the general trends and relationships between standoff and cost of protection. A number of the various components of incremental security cost are shown, including structural and non-structural component contributors.

Line chart of the impact of standoff distance on component costs. Between 0 and 20 the risk is high to catastrophic, between 20 and 50 the risk level is high to moderate, between 50 and the limit the risk is either moderate or high to moderate, from the limit on the risk is moderate to low. The total protection cost line (hardening + land + perimeter) has a high incremental cost of protection, dips at 20 standoff feet, and rises again to a higher than before level. The cost of hardening starts at a high incremental cost of protections at 0 standoff feet, declines steadily until reaching the limit then drops significantly afterward. The frame begins at 0 standoff feet at a medium to high level of incremental cost of protection, dips steadily to the 50 standoff feet mark and then levels out. Windows and walls begin at a relatively low incremental cost of protection, remain level until it reaches the limit and then dips. The progressive collapse line remains at a low level of incremental cost of protection. Other, mailroom, loading dock, and the lobby do the same only at a lower level.

Fig. 1. Impact of standoff distance on component costs. The relative magnitude and scale of these relationships vary from project to project.
Image Credit: GSA and Applied Research Associates

For example, the cost associated with hardening the mailroom, loading dock, and lobby to meet the ISC requirements is usually relatively small, and does not vary with the available standoff. The cost associated with progressive collapse considerations is also constant with standoff, since it is normally treated as threat-independent. There is a point at smaller standoffs where the framing design is further impacted by the blast loading on the frame, resulting in larger framing members and additional cost. This region is illustrated in the close-in regions, particularly within about 50 ft. As the standoff gets very small, costs increase dramatically.

The requirements for walls and windows are a function of standoff, as indicated for larger standoff. However, the ISC Security Criteria places limits on the maximum levels for which various components must be designed. The limits placed on the design blast pressure and impulse for the medium and higher levels of protection cap the cost at a particular standoff (limit) such that cost for walls and windows does not increase within this limit. It must be noted that this limitation in blast resistance in this region increases the inherent risk accepted with decreasing standoff.

The sum of the varying costs of hardening for the various components results in the "cost of hardening" curve indicated on Fig. 1. This function generally has a plateau between about 50 ft. standoff and the limit value for the relevant level of protection. At closer standoff, costs usually increase rapidly due to increased framing requirements. At larger standoff values, costs decrease to a plateau where conventional design requirements may govern.

One cost component that increases with increasing standoff is that for land (site area) and perimeter protection. For example, to provide increased standoff, the distance to the defended perimeter must increase, thereby increasing the area of the site and the length of the perimeter that must be protected.

Finally, adding the cost of hardening and the cost of land and perimeter protection results in the general function indicated as "Total Protection Cost". The characteristics of this function, with an increase at small standoff and increasing with larger standoff, indicate that a minimal cost may lie in a moderate range of standoff. At standoff values within the limit inherent in the blast design loads limits, the risk continues to increase with decreasing standoff. Nominal workable standoff values in the range of 20 ft. to 100 ft. are generally acceptable and achievable for GSA facilities. The risk and cost for standoff values less than 20 ft. generally are unacceptably high. Providing standoff values greater than 50 ft. can reduce risk further. A standoff distance of at least 50 ft. is generally preferred.

The figure and discussion above illustrate general characteristics of the cost and risk functions. Actual relative magnitudes and significance of individual cost components vary for each case considered, i.e., these relationships will be different for each building and site considered.

For information about physical security strategies, see WBDG Secure / Safe Branch, Designing Buildings to Resist Explosive Threats, and Retrofitting Existing Buildings to Resist Explosive Threats.


The designs resulting from application of the Interagency Security Committee (ISC) Security Design Criteria offer protection from smaller explosive threats and reduce collateral damage effects from larger threats. The blast design criteria provided in the ISC Security Design Criteria, focusing on smaller threats, reflects numerous years of experience in blast effects and constraints on current designs. The experience and constraints include:

Recognition and application of these facts and constraints leads to the following principles for blast-resistant design:

  • Take reasonable steps to prevent any collapse, if possible.
  • Minimize the potential for progressive collapse, regardless of threats.
  • Accept some additional risk by limiting design requirements for windows and walls.

These principles are reflected in the ISC Security Design Criteria and in the security-related costs related to its implementation. Structural component costs affected by the implementation of the blast resistance provisions of the ISC Security Criteria include:

  • Roof
  • Exterior walls
  • Exterior windows
  • Structural frame
  • Special areas

In addition to typical exterior windows, glazing affected by security considerations includes skylights, curtain walls, and ballistic-glazed windows. For information on mitigating glazing hazards, see WBDG Glazing Hazard Mitigation. Hardening of special areas such as underground parking levels beneath the building and loading docks and mailrooms add to security cost. Site-related security costs include vehicle barriers, perimeter barriers, and added site lighting. For additional information about site-related security see WBDG resource pages Effective Site Security Design, Site Security Design Process and Landscape Architecture and the Site Security Design Process.

The costs for all of the above-mentioned items must be accounted for in developing cost estimates. Further, designers may need to quantify other costs related to security requirements including, but not limited to:

  • Added signage
  • Site-related security measures—access driveway reconfiguration, barriers, bollards, loading docks, prevailing winds, protection of site utilities and infrastructure
  • Landscape design for security—topographic and/or vegetative visual control, physical and/or vegetative barriers
  • Strengthened interior doors
  • HVAC—raised air intakes
  • HVAC—redundancy of utilities
  • HVAC—protection of ventilation equipment
  • Emergency power protection
  • Telephone service redundancy
  • Separate/redundant water supply pumps
  • Backup control center
  • Security key system
  • Emergency duress stations
  • Other cost items.

Relevant Codes and Standards


Federal Guidelines

Additional Resources

Security Criteria Centers


  • Anti-Terrorism: Criteria, Tools & Technology  by Joseph L. Smith, Applied Research Associates, Inc. 2003.
  • Architectural Design for Security and Security and Technology Design by Donald M. Rochon. June 1998.
  • Building Security: Handbook For Architectural Planning And Design by Barbara A. Nadel, FAIA, Editor-in-Chief, 2004.
  • Designing for Crime and Terrorism, Security and Technology Design by Randall I. Atlas. June 1998.