NIST WTC investigation’s recommendations may make future buildings safer

­Future buildings, ­especially tall structures­, should be increasingly resistant to fire, more easily evacuated in emergencies, and safer overall thanks to 23 major and far-reaching building and fire code changes approved recently by the International Code Council (ICC) based on recommendations from the Commerce Department’s National Institute of Standards and Technology (NIST). The recommendations were part of NIST’s investigation of the collapses of New York City’s World Trade Center (WTC) towers on Sept. 11, 2001. The changes, adopted at the ICC hearings held Sept. 15-21, 2008, in Minneapolis, Minn., will be incorporated into the 2009 edition of the ICC’s I-Codes (specifically the International Building Code, or IBC, and the International Fire Code, or IFC), a state-of-the-art model code used as the basis for building and fire regulations promulgated and enforced by U.S. state and local jurisdictions. Those jurisdictions have the option of incorporating some or all of the code’s provisions but generally adopt most provisions.

“We applaud this historic action by the ICC­and the tremendous effort by NIST and its WTC investigation team that led to it,” said Commerce Secretary Carlos Gutierrez. “The lessons learned from the tragic events of 9/11 have yielded stronger building and fire codes for a new generation of safer, more robust buildings across the nation.”

“These code changes are the result of a strong commitment to public safety by the nation’s building and fire safety officials, private sector professionals and the fire service,” said Shyam Sunder, lead WTC investigator for NIST. “The improvements that they will ensure will be of lasting value to our society.”

The new codes address areas such as increasing structural resistance to building collapse from fire and other incidents; requiring a third exit stairway for tall buildings; increasing the width of all stairways by 50 percent in new high-rises; strengthening criteria for the bonding, proper installation and inspection of sprayed fire-resistive materials (commonly known as “fireproofing”); improving the reliability of active fire protection systems (such as automatic sprinklers); requiring a new class of robust elevators for access by emergency responders in lieu of an additional stairway; making exit path markings more prevalent and more visible; and ensuring effective coverage throughout a building for emergency responder radio communications.

Nine additional code change proposals based on the NIST WTC recommendations were not approved for the 2009 edition of the I-Codes.

These proposals address areas such as designing structures to mitigate disproportionate progressive collapse, mandating the use of a nationally accepted standard for conducting wind tunnel tests (routinely used for determining wind loads in the design of tall buildings), limiting the length of horizontal transfer corridors in stairways, installing stairway communication and monitoring systems on specific floors of tall buildings, and requiring risk assessments for buildings with substantial hazard (such as buildings more than 420 feet high with occupant loads exceeding 5,000 persons).

Summaries of the approved changes and unapproved proposals accompany this news release while detailed lists, along with a chart tracking the progress toward implementing all of the NIST WTC recommendations, may be found at

The leadership provided by the ICC’s Ad Hoc Committee on Terrorism Resistant Buildings, its Code Technology Committee and the U.S. General Services Administration were key to achieving the code changes. The proposals were developed and refined on the basis of feedback provided by building and fire code experts convened by the National Institute of Building Sciences (NIBS) with support from NIST.

“NIST remains strongly committed to continuing our work with these groups toward implementing additional changes to codes and standards based on our WTC recommendations,” Sunder said. “That effort also will include the recommendations from the recently completed NIST investigation of the collapse of WTC Building 7, as well as amending the unapproved proposals based on recommendations from the NIST WTC towers investigation for possible adoption during the next revision cycle for the I-Codes.”

As a non-regulatory agency of the U.S. Department of Commerce, NIST promotes U.S. innovation and industrial competitiveness by advancing measurement science, standards and technology in ways that enhance economic security and improve our quality of life.

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