Reversible building, modular building: what's the difference?

How to build less, but better and more sustainably – that is the question occupying the building industry. What if the answer lies in versatility rather than permanence? What if buildings were constructed to be polymorphic, made from materials that promote multiple uses? Reversible or modular – we take a look at construction that is adaptable as well as sustainable.

When adaptable beats permanent

Reversible buildings, modular buildings, deconstruction, rehabilitation, reuse – a growing number of terms are emerging to describe a living, evolving approach to construction, rather than one fixed in time. This change is a natural response, of course, to the time in which we live. Everyone’s focus – particularly in the building sector – is on the environmental challenge, preserving natural resources, combating the artificialization of soils... as well as the housing shortage and the paradoxical increase in the number of vacant buildings. Instead of providing pleasant accommodation for the range of human activities, a glut of poorly built, unsuitable and uncomfortable buildings actually seems to have impoverished our regions. But then how do you square the circle?

Buildings incapable of adapting to new uses?

French architect Patrick Rubin outlined the future of construction in his white paper Construire Réversible (Canal Architecture, 2017): “Our societies have built more in recent decades than in previous centuries and the prospects for transformations to be implemented are immense. Choosing rehabilitation over construction will soon be the rule.” However, if existing buildings are no longer suitable, rebuilding them would appear to be an equally daunting task: “A disproportionate effort is often required to give a building a new lease of life when it is devoid of magic and appears unsuitable for accommodating new uses,” continues Patrick Rubin.

But then, what other solutions are there? “The idea of ​​living, working, teaching, successively in the same space, involves separating the construction program and process from the design stage and prioritizing flexibility of use.” What Patrick Rubin is talking about is a reversible approach to construction, designed from the outset to have multiple different uses.

Reversible and modular buildings: what are we really talking about?

Modular, reversible – it is clear that the sustainable buildings of the future need to embrace concepts of flexibility and geometry.

But what is meant by reversible construction and modular construction?

A reversible construction is a building designed to serve several uses throughout its lifetime (from professional to residential and vice versa), without needing to be demolished. How? By favoring a “universal” design: either a large surface area, with spaces that are as open as possible, a solid wood or metal frame with a lighter inner lining (internal walls and partitions) and wood cladding, for example, which can easily be dismantled, adapted, redeployed and reused according to the intended use. Reversible construction means that each use must be considered in advance... And this is an approach increasingly being taken in new districts and those undergoing rehabilitation. In France, for example, in the Confluence district of Lyon, the Work#1 project being carried out by LinkCity and Bouygues Bâtiment Sud-Est, includes office buildings that will able to be converted into housing once the nearby motorway is downgraded to an urban boulevard in a few years’ time. VINCI Construction France has also developed Conjugo, a solution for constructing an office building that can be reconverted to housing. Reversible is becoming the new norm.

This approach is also gaining momentum in the Netherlands: the RAU Architects agency congratulated itself last January for having designed “the first large-scale office building 100% in wood and able to be entirely dismantled” for the Triodos Bank head office in a forest near Zeist.

A modular construction refers to a building prefabricated in 2D or 3D, designed in advance in the factory according to specific specifications and transported directly to the site to be assembled to form a building. By definition, modular construction can be adapted as desired and easily adjusts to current and future needs.

Although the practice has been around for several years already, quality and expertise have now increased in the modular market, especially in Europe, and it expanded to cover all uses – from the most modest… to the highly ambitious.

A fully modular multi-purpose stadium has recently sprung up in Abu Dhabi, for example: the Etihad Arena, on the man-made Yas Island. Saint-Gobain was chosen to fit out the building, designed by architecture firm Pascal+Watson, which will host a wide variety of sports and entertainment events ranging from a 500-seat theatre to an 18,000-seat arena.

In Germany, Saint-Gobain and SH Holz & Modulbau Gmbh rehabilitated the Stadtteiltreff Stroot childcare center in Lingen in just three months, using modules prefabricated in the factory and then assembled directly on site. This efficient method also proved useful during the Covid-19 pandemic, when China pulled off the feat of creating a new 1000-bed hospital in Wuhan using a modular design in just a few days.

                  TO READ: Less concrete, more gypsum and timber. Less time on site and greater flexibility. Is lightweight construction THE way to respond to climate change and demographic challenges?


Numerous advantages and few limitations

Why favor reversible and modular approaches today? Because both approaches can be adapted to any project. 

The main advantage of modular construction is that it allows maximum control over the quality of workmanship and the materials used. Everything is designed directly on the materials chain, avoiding a number of risks frequently encountered on many construction projects. Better still, manufacturing times are shortened, the number of intermediaries reduced and waste avoided – all advantages which also help to reduce costs.

With reversible construction, the main benefit lies in the savings in terms of resources. Each material must be chosen according to its circular economy credentials, since everything is designed eventually to be reused on another project. Less waste, less wasted resources.

What about limitations? Some do still exist, but they are no longer insurmountable. For modular construction, the main challenge lies in converting industry professionals: builders, and even architects, used to casting concrete need to adapt to new standards, a new economic model and a very different approach to design.

In relation to the reversible approach, the challenge lies in unifying standards and regulatory requirements, which currently vary according to the type of buildings (wall thickness, etc.), in order to make practices more consistent and streamlined. This is why only change of use from residential to office buildings is currently being considered, rather than healthcare buildings, which are more complex.

Materials at the center of new approaches

And what role do materials play in all of this? Should we move to everything being recycled and recyclable? The answer, for both reversible and modular, is that the trend is towards the circular economy. It is now impossible to consider a sustainable construction project without planning the building’s end of life or at least its next use. Priority must therefore be given to materials that are easy to dismantle, reuse and recycle, including metal structures, wood, plaster and recycled materials. But the approach is now being taken further. In Europe, reuse also implies the complete transparency of materials, based on a “materials passport” specifying the solutions used, how to assemble and dismantle them, their use and every substance included in their composition, in order to minimize future risks.

Whether reversible or modular, it seems that buildings of the future no longer aim to make their mark on the skyline, but rather to offer themselves as tools capable of evolving with the times. Rather than simply being a long-lasting building, this is undoubtedly what it means to be a truly sustainable construction.


Photo credit : Sergey Nivens/Shutterstock

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