Modular buildings: movable, interchangeable, but are they flexible?

Additive architecture has a mixed history, and pods are not exactly suited to creating open spaces, but plug-in buildings may offer other advantages

June 2021

Words by Tony Whitehead

The Nakagin Capsule Tower in Tokyo (1970). Kisho Kurokawa’s vision of interchangeable concrete modules proved a heroic failure
Photo Ned Snowman / Alamy Stock Photo

It is hard for even the most adaptable building to remain relevant indefinitely, particularly when the populations around them move and grow, and their locations take on new identities. Designers have always had a paradox to resolve: buildings tend to remain static in cities and societies that change constantly.

Tokyo’s Nakagin Capsule Tower was an attempt to solve this puzzle by creating the ultimate flexible building. Designed by Kisho Kurokawa and completed in 1972, its extraordinary design was born out of Japanese Metabolism, an architectural movement which, ahead of its time perhaps, viewed cities as organic, growing entities that required similarly dynamic buildings. The Capsule Tower was conceived with its concrete core acting like the trunk of a tree, and interchangeable modules sprouting like branches to provide a variety of functions: bedroom capsule, office capsule and so on. 

It proved a heroic failure. No capsules were ever exchanged because it was simply too difficult to remove and replace them. Ironically, the tower’s continuing existence owes more to fondness for its distinctively dated appearance than its ability to change with the times.

The ultimate flexible building

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Half a century later, modular building is now much refined and almost commonplace, each factory-finished unit usually forming a complete room that can simply be craned into place. It is a rapid, quality-assured type of construction that has proven ideal for creating hotels, student accommodation and more — but adaptability would still not appear to be its strong suit. As Kristian Ahlmark at Schmidt Hammer Lassen and WSP’s Audrey McIver point out, modules lack the long spans and open spaces that most designers agree are vital for future reconfigurations. Services, too, tend to be module-specific and tightly integrated into each unit, making them difficult to modify or replace.

WSP’s temporary quarantine accommodation in Penny's Bay, Hong Kong (2020). After the pandemic, the pods can be relocated and reassembled as social housing
Photo WSP

But even if modular buildings are not particularly adaptable, they may offer a different kind of flexibility. In Hong Kong, the government Buildings Department is encouraging greater use of what it refers to as modular integrated construction, or MiC. The first multistorey project to be approved was InnoCell, a 17-storey accommodation block at Hong Kong Science and Technology Park. WSP structural engineers helped to design a system that would deliver all the classic modular benefits of efficiency, reliability and speed — but with the possibility of wholesale replacement of plugged-in elements.

"Each steel module is simply bolted to its neighbours. If completely different modules were one day needed, then the existing ones could be removed from around the core, layer by layer"

Richard Chan-Hang Lee, WSP

When the block completed last year, it had taken at least six months less to build than a traditionally constructed equivalent. Metabolist-style flexibility was not the aim, but interestingly the concept is familiar: steel-framed accommodation units have been craned into position around a central concrete core and connected, one on top of another. Richard Chan-Hang Lee, WSP managing director of building structures in the China region, explains: “Each steel module is simply bolted to its neighbours. If completely different modules were one day needed, then the existing ones could be removed from around the core, layer by layer. They could, for example, be replaced by different-sized rooms by placing modules with one or more open sides adjacent to each other.”

Elsewhere in the city, WSP has used similar modular technology to enable the rapid provision of emergency pandemic quarantine accommodation. “For obvious reasons, this accommodation is positioned away from highly populated areas and the site would not normally be a useful residential location,” says Lee. “The advantage of using MiC here is that, after the pandemic, these units can be moved to a more suitable location to provide transitional social housing.”

This article appears in The Possible issue 07, as part of a longer feature on flexible buildings

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