Built to Last or Built to Fail? The contested causes of WTC 7’s collapse and implications for structural firefighting strategies

In our previous article, “Built to Last or Built to Fail?” (FSJA, March 2025), we covered some of the details of the National Institute of Standards and Technology (NIST) claims of the fire-induced collapse of World Trade Center building 7 (WTC7), on September 11, 2001.

That article covered the importance of firefighting confidence in highrise operational procedures, touching upon the investigations of the WTC7 incident by both FEMA and NIST, the building’s fire protection ratings and exposure to fire, what we know and accept about the performance of steel under thermal stress in relation to normal office load fires, and the documented history of modern highrise fires.

 It’s important to note that the FEMA and the NIST reports (both from two governmental agencies) did not agree with one another as to the cause of the collapse.

One of the responsibilities of NIST is to set structural design codes for buildings.

The NIST Report

The NIST Report, was published in November 2008. Understandably, most firefighters won’t be aware of this report and even less will have read it.

It’s an investigation based on computer modeling to arrive at its conclusions.

To this day, its data has been withheld from peer review and public scrutiny, in the interests of “public safety.” The computer modelling was used to reassemble a “virtual” WTC 7 building, and relied on the data it was provided to draw its conclusions.

The lead investigator, Dr. Sivaraj Shyam-Sunder stated: “We drew conclusions and validated them against video and photographic records.”

Dr. Sunder is also quoted as saying: “This extraordinary event, the collapse of WTC 7 was primarily due to fire…This is a new phenomenon, a new kind of progressive collapse that we have discovered here: the fire-induced progressive collapse due to thermal expansion.

“In fact, we have shown for the first time that fire can produce a progressive collapse… This is the first time that we are aware of, that a building taller than 15 stories has collapsed primarily due to fire. A rare event.”

These are profound statements.

So, why isn’t the American fire service studying what should be the most important case study in the history of highrise firefighting? The current 2021 edition of NFPA 1700, Guide for Structural Firefighting makes no mention of this newly discovered phenomenon, “fire-induced progressive collapse due to thermal expansion”.

Problems with the NIST Report

The first notable problem centers around the fact that NIST’s investigation did not use any physical evidence, only theories.

In clear contravention of federal laws and the most basic national standards set by the National Fire Protection Association, particularly – ‘NFPA 921-Spoliation of Evidence’ and ‘NFPA 921-Preservation of the Fire Scene and Physical Evidence’, almost all of the physical evidence was removed and disposed of.

NIST declared: “The collapse of World Trade Center 7 is the first known instance of a total global collapse of a tall building primarily due to fire.

“The collapse could not have been prevented without first controlling the fires before most of the combustible building contents were consumed.”

Yet, WTC 7 only had normal office combustible load levels ranging from 20-32 kg/m2, which was only enough material to burn for approximately 20 to 30 minutes in any given area, according to NIST.

These approximate burn times are consistent with the evidence shown in the video recordings and photographs of the day.