The Great Pyramid of Giza has stood at a height of around 460 feet for 4,500 years, but these days we are ripping down tall structures without even batting an eyelid. A new study looking at the average lifespan of demolished skyscrapers illustrates just how quick we are to pull the trigger, raising the question of how we could reimagine tower design so that they last centuries rather than decades.

What goes up must come down, and humanity has put up and pulled down some pretty big buildings since the emergence of the modern skyscraper around 140 years ago. The tallest of these was the 41-story Singer Building in New York City at a height of 187 meters tall (613 ft), which was pulled down in 1968.

This would be easily eclipsed today by the Burj Khalifa at 828 m (2,700 ft), but the Singer Building itself was the world's tallest building when completed in 1908. Will the mighty Burj outlive its early 20th century forefather? Plans to demolish New York's 270 Park Avenue offices, 216 m (708 ft) tall and currently 57 years old, don't quite qualify as a warning shot, but aren't irrelevant either.

That demolition job on 270 Park Avenue, which will make way for a bigger office for owner JPMorgan Chase, has incited a fair degree of controversy. This is partly because of the stature the building holds in the architecture community as something of an icon of mid-century design, and partly because of the role pioneering architect Natalie de Blois played in its design, working as she did within in a male-dominated field.

But the Council on Tall Buildings and Urban Habitat (CTBUH) sees it as significant in another way, as it would be the first time a building over 200 m (656 ft) has been peacefully demolished (the September 11 attacks on the World Trade Center being the non-peaceful exception). This threshold is significant, as architect and CTBUH journal editor Daniel Safarik explains.

"In many markets around the world, 200 meters is the approximate threshold beyond which the cost of adding a floor is exponentially more expensive per floor, rather than just arithmetically more expensive," he tells New Atlas. "The reasons for this mostly have to do with the extra structural bracing that is needed to maintain stability beyond that point. There are also costs associated with pumping concrete higher and getting construction workers, and later, occupants up and down in the building, which add to operational and construction costs."

So with 270 Park Avenue set to become the tallest tower ever pulled down, Safarik and his colleagues at the CTBUH thought it'd be a good time to take stock of our skyscraper destruction work so far. They conducted a study looking at the tallest 100 buildings to be dismantled by their owners, and found that on average they had a lifespan of just 42 years.

Most of these were taken down to be replaced by taller high-rises that make better use of space in increasingly dense cities and yield greater financial returns as a result. This makes obvious sense in economic terms, but are we giving enough consideration to the use of resources, environmental consequences and longer term impacts of an architectural trend that is only headed upward?

"We're building more and more of these very tall buildings," Safarik tells us. "In 1996 the world completed 10 buildings 200 meters or higher. In 2017 that number was 144. Cities are becoming megacities, with many tall buildings clustered together. If we're not planning these to have centuries-long lifespans, we're going to have a problem in 20 years.

"It's expensive to take buildings down, and there is always the question of noise, disruption, dust and loose particles, and even accidental catastrophic collapse during demolition," he continues. "The biggest issue, even if everything goes well, is that it is just an enormous waste of resources – concrete cannot be recycled, and most of the tallest buildings in the world use concrete for their main structural system."

Indeed, concrete is our favorite and most commonly produced construction material and therefore has a huge carbon footprint, with its key ingredient cement accounting for around eight percent of the world's C02 emissions. And that's to say nothing of the production of steel (also carbon-intensive) and other materials that go into these relatively short-lived structures. So how can we make skyscrapers that endure?

"Some of the trends that have already started to hit the industry are probably pushing us in the right direction," Safarik says. "Many skyscrapers in the 200-plus category are mixed-use, which limits risk in case of a weak market in office, hotel or residential. The building can still be operated even if partially vacant, and if zoned properly, unused areas don't have to be air-conditioned, etc.

"Other trends have just barely cracked the surface, such as modular and prefabricated construction," he continues. "A small number of tall buildings are built using the modular methods that are common now for motels and hospitals, and low-rise apartment buildings. Factory-made parts that can be bolted into place on-site are less wasteful in the first place, less costly and dangerous to construct on-site and, in theory they are easier to disassemble, should that become necessary. Another option is to add on top of the building if there is a positive demand that calls for more space as opposed to tearing it down and replacing it with a new building that is taller, which is easier to do with modular."

Examples of this type of two-phase construction do exist, most notably in the Blue Cross Blue Shield headquarters in Chicago. The 33-story tower was completed in 1997, only to be extended by 24 further stories almost a decade later.

"That was done using conventional construction methods – and some foresight," says Safarik.

And foresight would be key in not just reinventing existing skyscrapers for different uses, but in designing them for longevity from the ground up. Building tall and skinny to allow natural light to better penetrate the interior is one suggestion he offers, as is the use of high ceilings and open floorplans to maximize versatility.

"Speaking really generally, it basically comes down to investing more as a first cost in sustainable and recyclable systems, to save on maintenance or prevent premature obsolescence later," says Safarik. "The skyscrapers of today have a lot to learn from their pre-air-conditioned predecessors – natural ventilation, access to light, varied opening sizes and not just a wall of glass, in addition to attention to detail, have made the older buildings stand the test of time. That is, unless someone demolishes them to make way for a building that would turn a quick profit in 10 years, with no thought given to what will happen to it in 50 years."

The study can be accessed via CTBUH's website, and the source link below shows the full list of the 100 buildings analyzed in the research.

Source: CTBUH

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