French studio Lacaton & Vassal, which was today named the winner of the Soane Medal, demonstrates how architects can work with, not against, communities and existing buildings, writes Edwin Heathcote.

When architects Lacaton & Vassal were commissioned to improve the Place Léon Aucoc in Bordeaux in 1996 they didn't do much at all. In fact they left it pretty much as it was, with an instruction to do more regular maintenance and to replace some of the gravel.

It was, in its way, a pretty revolutionary move. This was the height of the icon, the age of starchitecture and architects were being encouraged to bring an injection of sculptural adrenaline to knackered cities. Instead, the Parisian pair studied the square carefully and found it worked pretty well, no need for change here. "It was not doing nothing," Ann Lacaton told me recently – "it was a commission. And to leave it was a decision."

 Never demolish might have sounded a little mad in 1996, but now it sounds visionary

Lacaton and Philippe Vassal, who have just been awarded the Soane Medal (which I was a jury member for), have made their name with their slogan "never demolish". It might have sounded a little mad in 1996, but now it sounds visionary. This was a practice that respected the already existing and sought not to replace but to repair.

They hit the headlines with their Pritzker Architecture Prize in 2021, but they had been making waves for two decades before that. First it was with their remarkable transformation of the Palais de Tokyo in 2002 (expanded in 2014), a stripping out of a classical/art deco exhibition hall to create a raw, haunting, cavernous interior which became Paris's riposte to London's Tate Modern.

The scarred concrete, the structure denuded of its classical aspirations and the vast spaces made for a perfect venue for art and action, creating a cool, ruthlessly stripped interior in a city of gilded rooms and fancy palaces.

Their next big impact though came with a very different kind of building, a social housing slab on the edges of Paris. At the Tour Bois-le-Prêtre in 2011 (working with architect Frédéric Druot) they re-clad an unpromising, albeit solid 16-storey 1970s slab in a diaphanous veil of cheap polycarbonate.

The striking thing here was that they left the residents in place during the works so that the community would not be disturbed and the inhabitants wouldn't become disengaged from their homes. The floor plates were extended with balconies and the building reclothed. Once tired and a little ragged, it became a beautiful thing, a translucent tower resembling a piece of avant garde modernism yet all for social housing tenants who had got used to not being consulted or cared about.

It was an extremely radical project and one which provokes the question of why it has not been replicated almost universally. It was done at least one more time in Bordeaux in 2017 to even more delightful effect, the architects wrapping a layer of winter gardens around the homes, an insulating layer but one which ingeniously gave the residents extra space without interfering with their floorpans.

Construction is fiercely carbon intensive so whatever can be saved should be

They added over 50 per cent extra floorspace to the flats as well as eight new dwellings, it resulted in construction costs of one third of a potential replacement and with half of that carbon footprint. All this for towers that were going to be demolished.

They had tested the language out at a house in Bordeaux in 1999 which saw a biscuit factory converted but also at another dwelling in Floirac a few years earlier in 1993. Here they created a basic house and fronting it up with a huge polycarbonate conservatory which imparted a kind of agricultural appearance, covering space as cheaply as possible.

They then went on to use similar ideas at their wonderful FRAC Nord-Pas de Calais art gallery where they created a kind of ghost twin for a derelict ship-building shed. Rather than renovating the existing shed they left it naked and a little decrepit, creating instead a mirror-image next door, again in cheap, translucent polycarbonate and left the old, 1949 structure as an epic shed for events and installations.

They can do new builds as well as anybody, just look at the architecture school in Nantes, a genuinely flexible, remarkably fluid building which has become a place of real communal activity. But it is their attitude to the existing that has made them harbingers of a new and not entirely uncontroversial moment for architecture.

If designers might be nervous about AI taking their jobs they might also (you would hope) be suffering from anxiety about the embodied carbon in the buildings they are destroying to get the opportunity of creating their new works.

Construction is fiercely carbon intensive so whatever can be saved should be. But what their work suggests, I think, is that architecture is almost invariably more interesting if designers need to work not only with existing structures and extant fabric but with existing communities, with people in place.

Much bullshit is spouted about "placemaking" but often the best places already exist

What might seem like a constraint is a reality check, a reminder that architecture is not a tabula rasa but that it intervenes in complex and delicate infrastructures of relationships and networks. As so many social housing projects in the UK have shown, once residents are "decanted" very few end up returning, whether by design or by fate.

Much bullshit is spouted about "placemaking" but often the best places already exist. The trick is not to screw them up. Lacaton and Vassal have illustrated how architects can work with and not against residents and communities, respecting not only the people and their memories but the collective memory of structures embedded into both the physical and the psychic landscape.

Architects are too often complicit in gentrification and social cleansing, whether unthinkingly or for reasons of pure commerce or ego. Lacaton & Vassal have shown another way. ‘"Demolition" Lacaton told me "is a form of violence". "Never demolish, always transform, with and for the inhabitants," she said.

The main image is of Transformation of 530 Dwellings by Frédéric Druot Architecture, Lacaton & Vassal Architectes and Christophe Hutin Architecture. The photo is by Philippe Ruault.

Edwin Heathcote is an architect and writer who has been architecture and design critic of The Financial Times since 1999. His numerous books on architecture include Monument Builders, Contemporary Church Architecture and the recently released On the Street: In-Between Architecture.