Building Skyscrapers post 9/11

The New World Trade Center 1 Tower — Freedom Tower

People around the globe know September 11th, 2001, as the day the world changed. Not only did the American government and large corporations alter their views and regulations on safety, but civilians across the nation, consciously or subconsciously, changed their way of life as well. Americans around the nation struggled to determine what the attacks would mean for the upcoming years and their lives would be impacted. One aspect of life that experienced immense change after the terrorist attack includes architecture. When Americans reflect on the infamous day, most are so overwhelmed with sorrow for the lives lost and anger towards the offenders that they do not process the action of the towers falling and what contributed to the two massive steel buildings collapsing. The collapse of the building has caused architects, engineers, and government officials alike to reevaluate the safety regulations for skyscrapers to ensure that the buildings can endure strong opposing forces and to guarantee that people can more easily evacuate in the face of tragedy. Moreover, the attack on 9/11 has instilled fear in people from around the world and has caused people to shift their perception of skyscrapers from being strong and beautiful buildings to being targets of terrorism and destruction.

In order to understand the changes to the industry post 9/11, one must understand the previous building safety requirements and design of the two towers of the World Trade Center. The two towers were built from steel columns following a tube-frame structural system with a Vierendeel truss. Fireproofing insulation then covered the steel columns and trusses to prevent damage to the steel for up to four hours. Usually, skyscrapers of that magnitude have their beams covered with concrete to reinforce the stability, but the design of the World Trade Center towers, along with many other skyscrapers being built at the time, called for the steel to be enclosed by drywall. Nonetheless, the building conformed with all codes and safety requirements and was capable of withstanding the toughest natural disasters. However, when the plane struck the two buildings, the impact easily compromised the drywall and the fireproofing coating which allowed for the fire to significantly weaken the steel column structure. The sprinkler system pipes were then disengaged and could not help tame the fire. Without the support of the steel body, the weight of the tower overwhelmed the structure, causing it to collapse.

After seeing how the building and people inside it responded to the attack, several regulations were imposed upon builders, and builders also starting going beyond regulations to not only make sure their skyscrapers would stand the best chance against any massive force but also to make it easier for those trapped in a building to escape. In order to generate new safety requirements for the buildings, the National Institute of Standards and Technology conducted a report in which they interviewed thousands of people, some of whom were in the building during the attack and others who are experts on architecture and structural engineering (Krohe 2006). A few minimal revisions made after the report included relocating the sprinkler system pipes within an impact-resistant barrier and mandatory glow in the dark exit signs in each stairwell. Other more-costly regulations on skyscrapers and high rises in New York City include having a separate staircase for firefighters and widening the current staircases. Furthermore, when rebuilding the One World Trade Center, now known as Freedom Tower, the architects took into consideration the flaws of the original tower and strived to make the new tower more resilient than the previous. The architects and engineers accomplished this by surrounding the steel spine of the building with a six feet thick layer of extra strong concrete instead of the weak drywall.

Another part of the industry that the attacks on September 11th altered includes the attitude of architects and engineers when designing buildings. Before when developing the design of the buildings, authoritative figures had considered how the buildings would hold up in cases of devastating natural disasters; however, after the attack many architects and engineers began to think more about safety in extreme circumstances such as terrorist attacks and bombings. The public then wondered if developers would continue to build skyscrapers, and if so at what pace after the attacks. Social critic and author James Kunstler went as far to say that “the age of skyscrapers is at an end,” and business gurus such as Donald Trump began to scale back the height of their upcoming towers (Lott 2011). In addition, Henry Petroski, an engineer specializing in failure analysis, stated in his article titled The Fall of Skyscrapers that “although the idea of the skyscraper is modern, the inclination is not” (Petroski 2002). In other words, while the concept of building skyscrapers is an upward trend, architects and engineers remained hesitant about designing tall towers after seeing two massive structures brutally destroyed. Regardless, the building of skyscrapers continued because of the economic advantage they possess; so, developers of upcoming tall buildings had to go to extra lengths to enforce a sense of security on the higher floors so that residents would feel capable of escaping if need-be.

In the architectural world, the attacks that happened on September 11th did not only mean change in building structures was needed but also meant that a challenge for new innovation was ahead. Even though the buildings were structurally sound, the general public’s perception of skyscrapers in major cities changed from being seen as strong and stable structures to being seen as dangerous targets of terrorism. While other communities struggled to determine the meaning of the attacks, developers were determined to display the strength of America to our enemies by rebuilding taller and stronger buildings.


Krohe, J. (2006). Tomorrow’s Skyscraper-Safety is trumping design. Planning Chicago- 72(7), 6.

Lott, M. (2011, September 11). After 9/11: How To Build A Safer Skyscraper. Retrieved September 19, 2016, from

Petroski, H. (2002, January). The Fall of Skyscrapers. American Scientist, 90(1), 16–20. doi:10.1511/2002.13.3329