The act of renovation and refurbishment within congested urban contexts means a degree of disruption—to the people living there, the infrastructure and the landscape. While reuse, repurposing and revitalisation exercises present themselves as viable solutions to reinforcing the demand for amenities in ‘developing’ cities—defined by unprecedented levels of urbanisation and growing pressure on land and resources—these strategies must still contend with the issues of congestion, oversaturation and urban sprawl that most cities in the world today are privy to. Cities were and continue to be palimpsests of different regulations, populations, cultures and policies; a challenge to the tabula rasa model of development.

How do we build in contexts that are historic and layered, congested, or otherwise difficult to access to alleviate existing conditions? What are the ways in which design can act as a tool to revitalise derelict and underutilised neighbourhoods? For the People’s Architecture Office (PAO), this contention, which is emblematic of the rapidly urbanising regions of China, presented a unique problem. An international practice with offices in Los Angeles, Beijing and Shenzhen, the firm was founded in 2010 by James Shen, He Zhe and Zang Feng. In their practice, the Chinese architects focus on fostering social interaction. In response to the need for housing and the particular contexts of the Chinese city, the studio developed a unique system of prefabricated architecture, which is dubbed ‘plug-ins’.

Much like software plug-ins (from which the construction system derives its name), the design approach employs prefabricated elements that can be slotted into existing structures to upgrade them while eliminating waste on site and the displacement of social fabric. The studio first showcased the proposal in 2016, with the Plug-In Tower, as a means to tackle the ‘future of housing’ within the context of historic areas in Beijing. The prototype was conceived as an infinitely expandable model with a steel space frame into which parts could be slotted, inspired by Metabolist principles, as mentioned in the official release for the experimental design.

Since the pilot, the studio has gone on to work on different residential projects that rejuvenate Chinese architecture in older parts of the city through addition and have employed the system as a way to think about the adaptive reuse of structures for different typologies, such as cultural centres or public buildings. In 2020, PAO spun off as the Plugin House Company to specialise in developing low-cost prefabricated homes as products, working in the United States.

The need for equitable housing is tantamount in today’s age. Moreover, if there are ways of providing the vital amenity that are low-cost and don’t add exponentially to the waste generated by the construction, these are worthy cases to study. In order to explore the genesis, processes and the future of the plug-in to address our growing demands, STIR spoke to James Shen, one of the principals of the Chinese architecture studio. Edited excerpts of the conversation follow.

Mrinmayee Bhoot: Could you start by speaking about some of the architectural influences which informed your approach to ‘plug-in’ architecture? The first that comes to mind is Archigram’s Plug-In City.

James Shen: I can start by talking about my training. My undergraduate degree was in product design. I was a furniture designer for some time before I started my architecture studies. Much of the approach that [PAO] has towards architecture and design draws from industrial design. And of course, there's a long history of that in modern architecture as well.

And I think architects [in the ‘60s] were also interested in incorporating ideas of industrial design—such as prefabrication, mass production, modularity—into architecture. Except that their ideas were more utopian in nature. That era was very tumultuous, which resulted in groups like the Metabolists, Archigram and Archizoom. For us, this work started in Beijing, also at a period in China where rapid change was happening. Part of our work was in response to this reality and this fast pace. Other influences, I would say, are also people I encountered while I was a graduate student; people like Joan Jonas or Krzysztof Wodiczko. These are artists who explore urban interventions and performance-based works in public spaces. So the idea that you have a given condition within which you insert something that hopefully improves things or reveals other modes of existence and movement was also a big influence on us.

Mrinmayee: Could you elaborate on the development of the idea and its various implementations?

James: In the past, we’ve implemented a wide range of applications for our plugin system. But the first projects we did were aimed at revitalising historic areas in the country. The urban fabric in these areas is quite informal. They're places where you have a lot of low-income population and we call them hutong areas. Generally, they are not areas that have seen a lot of preservation efforts for maintenance and upkeep of their historic quality.

[When we started working here], we wanted to devise an approach that did not involve relocating people and entirely rebuilding. We felt that people might be adversely impacted by this disruption. We found that to be a pretty interesting challenge. So that's what brought us to the idea of building a house inside a house. And our philosophy is not to ‘renovate’ one of these historic buildings, because when you renovate, you're also destroying, right?

In their current form, they are an aggregate of many changes, time and period-based factors, and many additions to their original footprint. There's also the factor of property that these courtyard houses—which were originally perhaps housing one family—might over time have been divided into various properties with complex ownerships. They are not consistent in their building process or material choices. If you're renovating, you have to choose, right? And when you choose, you're limited in terms of the kind of materials and processes you can work with. For instance, a lot of these structures are built out of a kind of hardwood from Southeast Asia that is just not available anymore.

In those situations, the question is, how do you try to improve things? So all these different factors led us to this approach, where we said— we're just going to build a house inside a house. We're going to upgrade the property for modern living conditions so that people can live more comfortably—bring in modern bathrooms and HVAC systems—while retaining much of the original structure. And if there are things that we felt were unsafe in the original structure, then we would reinforce those.

Mrinmayee: This makes me curious to understand the process of intervention for the plug-ins. Could you speak about the methods by which you make these historic spaces adaptable for modern living conditions?

James: There are different approaches that we've taken with our system. So if we're talking about the house-in-house approach, which is you have an original structure, we're upgrading it. Our system consists of these panels, which are prefabricated in a factory and they come with connections around the perimeter. You use a hex wrench to lock these panels together. There's no cutting, nailing, sawing, or even welding. When these panels arrive on site, they are placed into the positions that they need to be.

They already incorporate electrical panelling in them. Similarly, windows and doors are already incorporated. So you can build really quickly. What’s most important for the system is that components are small in size. In hutong areas, where you have narrow alleyways, you have to bring these in by hand and you're going into small doorways that have sunk into the ground with time. The way that this system improves the pre-existing conditions is that the panels are made out of a high-density foam insulation [which] makes these buildings way more energy efficient.

We've incorporated mini-split HVAC units with heat pumps so that they can heat and cool in an efficient manner. We've also incorporated composting toilets, or in larger properties, we would have a septic system installed in the courtyard that is self-sufficient. I believe our system is unique in that way as we can customise pretty easily.

Mrinmayee: Since you talk about customisation and intervening within what could be called difficult contexts, I’m also curious about the challenges that you may have faced, not just in terms of construction, but trying to convince stakeholders about the viability of an intervention such as this.

James: Yeah, that's been a very interesting process. These were first done as a pilot that was funded by a local government. They were testing out a policy for properties so that people can renovate partial sites. Because, as I mentioned, you have many owners under the same roof. Traditionally, there’s no way to renovate something that is subdivided in such a manner. I believe this is a common condition for many Indian cities as well, like Dharavi, maybe. So many cities in the world demonstrate similar conditions: you tend to subdivide plots because there's not enough housing or people live in older buildings because of the low cost and proximity to the city centre. We were lucky to be a part of this pilot and we ended up moving our office to this neighbourhood so that we can have a closer connection to the project.

Now we're about 10 years into the development of the system. We've separated this work into a separate company, the Plugin House Company, which is registered in the US. We're focused on promoting this in the US now, because I believe there’s a stronger demand for this kind of smaller housing here, while in China, the increasing population density means that most people have shifted into skyscrapers.

Part of us doing this in the US is that we need to raise enough funds for testing and obtaining certifications. The two major factors are fire and structure. Before, because we were working on pilot projects, we didn't have to go through a formal permitting process. We were able to do quite a few projects, which were directly approved by local officials. But to be something that you can put into the market, it needs to be a product. So those are some of the challenges in creating a new system. There are no building codes that govern this and navigating the whole process of a new kind of system and material, and a new sort of structure means you have to navigate all the regulatory requirements. So that's been a big challenge.

Mrinmayee: How do you negotiate differences in the surroundings, local climate and typology with the different projects you work on using plug-ins?

James: Adaptability is so crucial and I'm glad you asked that. Especially for our time, the kind of changes in the urban landscape that we're experiencing are just incredible. Architecture has difficulty adapting to these factors as well: financing, property, regulation, apart from rising populations, resource scarcity and climate change. We need to be designing with that mentality in our minds. And actually, we learned this from observing how people live in these informal areas. They are constantly adapting to improve their situation, except most times, they don't have all the tools that we have on hand.

It is not an accident that people everywhere have these concerns about housing. The problems we share are so similar. I think it's really interesting that this system is something that we started developing in China because of those urban conditions and then here in the US, it's also extremely relevant because of the urban conditions. In the case here, actually, most of the plug-in houses are used as independent, detached residential designs.

But one of the things that people are pushing here is the ability to build more on your own property. So that is subdividing property. And it's also something that you find in a lot of informal communities. We recognise that we have to densify. And how do you do that if you don't have a system that is nimble enough to go into a person's backyard and to fit into all these different shapes, properties and be easily transported and erected? Our typical ways of building don't really allow for that.

Mrinmayee: In Archigram 10, you envisioned your version of the Plug-In Megacity, writing, “The city is the megastructure, constantly adapting, always alive with spontaneous social activity and continuously densifying to allow more people to live where they most want to live.” Could you maybe elaborate on how you think of the future of the plug-in?

James: I really like the idea of architecture being woven into existing conditions. I think the way that a lot of people have previously thought about architecture was as a blank slate. Now we know that there can be many negative aspects to this kind of thinking. It's just not sustainable. When I say what's already there, it's not just the buildings, it's also all the people. If your contexts are drastically transformed due to rapid urbanisation, is it possible for us to have radical change, but that is woven into what's already there?

The megacity proposal was meant to convey a bit of that thinking. We have some drawings where we've tried to represent this and the drawing that you're referring to imagines how we can build onto our highways and roads, if they were no longer necessary. I did mention a lot of the work from the ‘60s and ‘70s that looked at this radicality, but I think even then, the idea of an existing context was not so present. Today, it's something that we are confronted with even more urgently.

We've gone through such a long period where the automobile drove how we designed our cities and structured society. But today, I do think there is a better appreciation for being more connected. In the US, we've been struggling with how we’ve planned cities historically, such as through redlining practices, where we segregate populations from each other using infrastructural means. What happens then is that if your urban planning is car-based and you're developing on cheap land, you're attracting people of a certain social class to locations where you don't have the kind of support structures and opportunities and networks that the city centre does. It leads to thinking about development in a very fractured way. So today, it's become very much the culture to embrace sprawling cities.

In this vein, when we say plug-in, we think of it in a larger sense. We think of a plug-in in terms of software, where you're adding to something that is kind of a hack, which is added onto something that's existing and improving it. I don't feel like we're saying anything new; we're just drawing attention to prevailing conditions and the existing ways in which cities have been built, with many different layers. That is, in fact, how we've naturally built our cities. Then, through modernisation, we let go of that. It's a limitation of our imagination rather than technology. I think culturally we need to be able to accept that our most interesting cities are those that have all these different layers and a mix of cultures. We need to foster that richness.