Modular construction and cities

17 November 2017

Modular construction techniques have been around for decades but are increasingly being used for high-rise buildings. From China to downtown Brooklyn, are we entering the age of the prefab skyscraper, and what does this mean for our cities? Patrick Kingsland asks Zhang Yue, founder and chair of Broad Sustainable Building; Christopher Sharples, principal at SHoP Architects; Rory Bergin, partner at HTA Design; and John Quale of the University of New Mexico.

The T30 Hotel in China’s south-central Hunan province has few distinguishing external features. It is flat, grey and towers over one of China’s bleak, sparse industrial economic zones. But the 30-storey, 17,000m² building is remarkable for another reason: how quickly it was built.

Ground was broken on the site of the high-rise hotel in December 2011 and construction was completed on New Year’s Eve, just 15 days later. A time-lapse video of the process – viewed on YouTube nearly three million times – is nothing short of remarkable.

“Humans have invested heavily in a lot of areas like aviation, transportation and communication but, on building sites, the investment is so small,” says Zhang Yue, chair of Broad Sustainable Building (BSB), the company behind the hotel. “At BSB, we are doing things differently.”

High ambitions

To accomplish the feat, Zhang opted for modular construction, where individual components are manufactured off site and then transported to the building site for assembly. The technique – used by celebrated architects from Buckminster Fuller to Frank Lloyd Wright and Richard Rodgers – has been around for decades but is now increasingly being used for high-rise towers.

In 2015, BSB built the world’s largest modular building, the 57-storey Mini Sky City, in just 19 days. While plans have stalled on a project to build the tallest skyscraper in the world using modular technology, Zhang hasn’t given up hope.

“We plan to build it in a few years to promote our factory-made sustainable buildings,” says the bullish, notoriously bad-tempered chair.

In the US, the tallest modular building is currently 461 Dean, designed by SHoP Architects and completed last year in downtown Brooklyn. Also known as B2, 60% of the 32-storey residential complex was constructed in a factory, says Christopher Sharples, principle architect at SHoP.

“With traditional buildings, you cannot start one trade until the other is completely done,” Sharples explains. “That means a drawn-out, uncollaborative and, in some cases, adversarial process. With modular housing, you move everything into the factory, where you can mix the trades. The electricians can work with the plumbers, who can work with the iron workers, and so on. Everyone is working together, eking out efficiencies.”

Productive construction

Working on and off site at the same time makes the whole process more productive, Sharples adds.

“With modular, you can build the parts on site and simultaneously start the construction of the modules in the factory,” he says. “It is a parallel process that we believe might have been able to save three to four months on the overall construction schedule [of B2] and 15–20% on hard construction costs.”

In the UK, where the largest modular tower in Europe has recently been completed, these factors are particularly important.

“The construction market is working at full capacity,” says Rory Bergin, partner at HTA Design, architect of the tower, which is called Apex House. “There are situations where clients are issuing tenders to contractors and getting no responses.

“You’ve also got skills diminishing,” he continues. “The Farmer Review into the UK’s construction market highlighted the number of people in the sector who are over 50 and going to retire in the next decade or two. It is a large proportion of the construction industry. With the barriers to immigration that Brexit is likely to bring, we will also have less foreign labour coming in to pick up the slack.

“Put together, these two elements are driving people towards a more productive approach to construction; one that can give them a product on time at a higher quality than traditional buildings.”

Environmental improvement

By reducing activity on building sites, Sharples also believes that modular construction can improve the everyday lives of citizens.

There should be no reason for modular buildings to look better or worse than any other type of building. It is down to the skill of the designer.

“Normally, everything gets delivered through the job site,” he says. “If you are working on a project in New York that creates a lot of congestion, that means a lot of pollution and a lot of noise for everyone who lives around the site. This usually goes on for about 18–24 months – sometimes longer. With modular, we can move a lot of that congestion into the factory.”

According to a study by John Quale, professor of architecture at the University of New Mexico, modular construction can also have a positive environmental impact.

“This is largely due to a decrease in the hours the employees work on the buildings,” Quale says. “Because it goes faster, they don’t have as much commuting time, which substantially reduces carbon emissions.”

Construction complications

Despite the benefits, however, modular buildings don’t always go to plan. Projects that require repetitive units – from motels to high-rise towers – are relatively simple to construct, but, deviate from that, and things can go wrong.

The triangular plot of land on which 461 Dean was built, for instance, required 32 different base modules. That complexity led to multiple delays and a bitter legal battle between the developer, Forest City, and Skanska, the construction company overseeing the work.

Quale says this is unusual, however. In most cases, “once you get to a high-rise project, you are going to have a very sophisticated engineer who truly understands it”, he says. “It tends to be the lower-end, two-or-three storey motel-type projects where things go askew. It happens when they haven’t addressed the structure appropriately.”

Like Zhang’s T30 hotel, modular buildings are also often accused of being repetitious and boring-looking. For Bergin, that is because, in the past, they were mainly used for emergency and site accommodation.

“The mistake has been that, in some cases, people have tried to use those temporary structures for other uses,” he says, adding that ugly buildings can be easily avoided.

“There should be no reason for modular buildings to look better or worse than any other type of building,” Bergin says. “When it comes to the design, what you are manufacturing is really the structure and base fabric of the building, none of which is visible from the outside. That gives the architect a pretty free hand in terms of the modelling of the structure and the cladding system. It is down to the skill of the designer.”

A question of efficiency

Arguably the biggest challenge facing modular construction is whether it can provide affordable housing on the back of efficiency savings. Its proponents claim it can but, in the short term, Bergin admits that “the scale of manufacturing” is simply too small to tackle the problem.

“At the rate they are currently building, you can’t get much of an economy of scale and you can’t drive the costs down,” he says. “In London, the cost is comparable with traditional construction and, in the rest of the UK, it is likely to be more expensive.”

For Quale, prices will only fall when the right developers show interest.

“In many cases, developers come in with a motivation to make profit,” he says. “They see that they can save money in the construction phase and still charge the same amount for something comparable.”

This cuts against the history of modular construction, Quale adds, which was often radical and socially ambitious. In post-war Japan, for instance, the Metabolists designed modular architecture that treated buildings and cities like living beings that could change shape and form.

In the UK, a radical architecture group called Archigram produced drawings that included the concept of a ‘plug-in city’ – a modular, reprogrammable urban space tied together by a system of giant construction cranes.

While these projects were largely hypothetical, Quale believes that modular towers can benefit ordinary people.

“If an affordable housing development corporation were to take this on – and there have been a few examples of that – people would reap the benefits of it,” he says. “It seems like a huge opportunity for people to live in a reasonable home and not have to pay a huge amount for it.”

In China, Zhang is typically confident. “We are looking for partners to construct the tallest buildings in the world in the US, Europe and Asia,” he says. “With such a low cost and high longevity, it is inevitable that we will disrupt the whole building industry.”

Modular construction enabled the T30 hotel to be built rapidly.
Mini Sky City in Changsha, Hunan, China.

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