Peter Franklin is Associate Editor of UnHerd. He was previously a policy advisor and speechwriter on environmental and social issues.

If a city can’t grow outwards, then it has to grow upwards – tearing down older, shorter buildings to make way for newer, taller ones.

That’s the theory and in a few cases it might even be true. In the core districts of our global cities, the skyscraper is the obvious response to the demand for more space.

However, space is all it supplies – because the concept of the ‘vertical city’ (i.e. a self-contained ‘community’ within a single building) is to stretch the definition of ‘city’ to breaking point.

The etymology of the word goes back a long way. There’s the old French cite and, before that, the Latin civis (meaning ‘citizen’). Go back even earlier and there’s the Proto-Indo-European word *Kei-wi meaning ‘member of a household’. This itself is derived from the root word *Kei meaning ‘to lie’ – a household being made up of people who lie down to sleep in the same place. (*Kei is also the origin of the word ‘cemetery’ – i.e. a place you are laid to rest.)

The city is an essentially horizontal concept. It is the spreading network of streets that turns a settlement into something more than the sum of its parts. But while the true city – the horizontal city – is all about connections, the vertical city is all about separation. The arterial function of the street is replaced by that of the elevator – literally and metaphorically an instrument of top-down control. Separate elevators, even separate entrances, keep the different sections and levels of the vertical city fundamentally disconnected. No wonder this form of architecture is so attractive to foreign investors who see global cities as a place to put their money, not a place to be a part of.

The false promise of the vertical city By Peter Franklin

There’s another yawning divide between the two concepts of the city. The horizontal city, being made up of discrete structures within easy reach of the street is much easier to physically modify than the vertical city – a single giant structure, stretching up to the sky.

The point is made in a fascinating article by Travis Barrington for Propmodo. He explains that ageing skyscrapers can be very expensive to maintain, while being impossible to upgrade:

“Built in an era of cheap energy, many post-war Manhattan towers have facades of single-glazed glass, and structures that can’t support the weight of additional insulating glass. Many have low ceilings, tight column spacing, and inefficient heating and cooling systems. Often these have become even more cramped by having to accommodate the infrastructure of modern information technology.”

Unfortunately, they’re also exceedingly difficult to demolish – thanks to their sheer size and height.

The author tells us that the tallest building ever demolished was the 41 storey Singer Building in 1968. There is, however, a grim qualification to that record – the Twin Towers of the World Trade Center destroyed on 9/11.

Barrington goes on to quote Antony Wood of the Council on Tall Buildings and Urban Habitat:

“There’s really no precedent for tearing down 200-meter-plus towers. We should perhaps thus be thinking of tall buildings as perpetual entities with lifecycles potentially exceeding 100 or 200 years, while designing them in such a way that they can be creatively adapted for potential future uses.”

Unfortunately, many skyscrapers look set to reach the end of their useful lives on a much shorter timeframe.

That, of course, is the vertical city’s fatal flaw. Each edifice represents a massive all-or-nothing bet on its continuing relevance. The city’s sustainability is entirely dependent on a single set of architectural, technological and commercial judgement-calls.

Each of the buildings that make up the horizontal city can also be seen as a bet on the future. Except that these wagers are smaller in size individually and broader in spread collectively. Not all will succeed, but when they don’t, it’s easier to learn from those that do and make a fresh start.

That’s why the horizontal city endures – both failing and succeeding, but always adapting.

The vertical city, however, is too big to fail. Except, that sooner or later it will. And then what?