Founded by Katerina Dionysopoulou and Billy Mavropoulos, Bureau de Change is shaped by a shared curiosity for material, process and the unexpected. Rather than working towards a fixed visual language, their approach begins with what is already there: the history of a building, the particularities of a site, the behaviour of a material or the knowledge embedded in a process of making.
For Architectural Reveries, Katerina and Billy reflect on friendship, the influence of Athens and London, homes shaped by family, memory and an architecture experienced through touch, sequence and time.
01/ How does your day typically begin? Is there a ritual or moment that sets the tone for the day ahead?
Our day usually begins before the working day officially starts. We are close friends as well as business partners, and we make a point of meeting at the office a little earlier, before everyone arrives and the pace of the studio takes over.
It has become a small ritual for us — we have coffee, catch up on life, talk about our families, what is happening outside work, and inevitably what is on our minds about the studio and our projects. The conversation moves very naturally between the personal and the professional, which perhaps reflects the way we have always worked together.
That time has become incredibly precious to us. Once the day begins, there are meetings, decisions, conversations and all the usual demands of running a studio. Having that quiet moment together beforehand gives us space to connect as friends, not only as partners, and somehow sets the tone for everything that follows.
02/ How do you best enjoy your time at home?
We both love to entertain, so our homes are very social spaces. We enjoy cooking, having friends around and the sense of the house becoming animated when it is full of people. At the same time, home is also where we retreat to our close family units and find moments of quiet. We have tried to create environments that can accommodate both — spaces that feel generous and open when shared with others, but intimate and calm when it is just us.
Our homes are quite personal and, in a way, continually evolving. We are surrounded by objects we have collected over time — some old, some new, some designed, but many simply things we have found on our travels. What connects them is rarely their material or monetary value, but the memories they carry: a place, a person, a particular moment in our lives. Ultimately, those associations are what give an object its greatest value to us.
We think of our homes as being curated, but not in a precious or static sense. They are curated around the way we want to live — around family, food, conversation, rest and the pleasure of sharing a space with friends and guests.
03/ Athens and London both form part of your personal and professional histories. What has each city given you?
Athens has given us an instinctive relationship with materiality, history and informality. It is a city where different periods sit visibly on top of one another and where buildings are constantly being adapted and appropriated. There is a looseness to the way the city is inhabited that has definitely stayed with us.
London gave us something quite different: an extraordinary concentration of ideas, cultures and disciplines, but also rigour. It was where our professional lives really developed and where we learned to operate at very different scales and levels of complexity.
Our work probably sits somewhere between those two conditions — the precision and discipline we learned in London combined with something more instinctive and sometimes unexpected that comes from Athens.
04/ You met at Foster + Partners and began talking early on about one day working together. What did you recognise in each other at that stage?
We recognised quite quickly that although we approached problems differently, we were interested in many of the same things.
There was a shared curiosity and an ambition to question the obvious solution. We were both interested in architecture beyond style — in how an idea could run through everything from the organisation of a building to the smallest detail.
At the same time, our differences were useful. We challenged each other, and that became part of the attraction of working together. Bureau de Change eventually grew out of that dialogue. It still works in much the same way today: an idea is tested from different positions until we arrive somewhere neither of us would necessarily have reached alone.
05/ You have said that although your projects look different, your design methodology remains consistent. What stays constant from one project to the next?
We always begin by trying to understand what is already there.
That might mean the history of an existing building, the particularities of a site, a material, a manufacturing process or even a social condition. We are not very interested in arriving with a predetermined visual language and applying it to different situations.
Instead, we look for something specific that can become the generator of the project. Once we find it, we explore it quite obsessively — through research, drawings, models, materials and prototypes — and allow it to operate at different scales.
The outcome can therefore look completely different from one project to another, but the process is remarkably consistent: observe, identify, test, transform.
06/ Material research begins very early in your process. What are you looking for in a material?
We are interested in what a material can do rather than simply what it looks like.
Every material comes with its own behaviour, limitations, history and methods of production. Often the most interesting moment is when you begin working with those characteristics rather than trying to suppress them.
We also like materials that register time. Stone wears, timber changes colour, metals oxidise and develop a patina. Those transformations give buildings and objects another life beyond the moment when the architect finishes them.
Material research for us is therefore both technical and sensory. We want to understand how something is made, but also what happens when you touch it, when light moves across it and when it has been used for ten or twenty years.
07/ You describe the element of surprise as central to your design process. How do you approach it?
Surprise for us is not about spectacle. It is much more interesting when it comes from discovering something that initially feels familiar and then behaves in an unexpected way.
It might be a conventional material used differently, a shift in scale, a hidden space or a detail that only reveals itself when you get close to it.
We often work through repetition and systems, establishing a certain logic and then finding moments where that logic can be disrupted. The surprise becomes more powerful because there is something recognisable around it.
We like architecture that doesn’t reveal everything immediately. There should always be another layer to discover.
08/ You have spoken about the journey from first seeing a building, to holding the door handle, to moving inside. How does this journey inform the way you design?
We think about architecture as a sequence rather than an image.
There is the moment you first encounter a building from across the street, then the moment you approach it, touch it, open a door and finally occupy it. Each of those distances gives you different information.
From far away you might understand proportion and silhouette. As you move closer, material and texture become apparent. At the scale of the hand, suddenly weight, temperature and tactility matter.
We enjoy designing across those scales and creating relationships between them. A detail shouldn’t feel detached from the larger architectural idea. Ideally, the experience of holding the door handle somehow contains the same thinking as the building itself.
09/ Beyond architecture itself, what are the people, places or experiences that continue to inspire you?
We find inspiration in disciplines where there is a very direct relationship between making and material — art, furniture, fashion, industrial design and traditional craft.
Travel is important too, but often it is the incidental things rather than the monuments that stay with us: a particular threshold, an old shopfront, the way stone has worn on a staircase, a chair in a taverna, the colour of a wall after years in the sun.
We are also fascinated by processes of making. Visiting workshops and speaking to craftspeople or manufacturers can completely change the direction of a project. There is something very powerful about knowledge that has accumulated through making the same thing repeatedly and refining it over generations.
And then there is everyday life. Watching how people actually inhabit buildings is endlessly instructive. People inevitably adapt architecture, and those adaptations are often more interesting than what was originally intended.
10/ Looking ahead, what questions are you still trying to explore through architecture, objects and the way we live?
Increasingly, we are interested in how we can make less, but make what we do more meaningful.
Architecture has traditionally been associated with adding something new, but some of the most interesting questions now are about what already exists: what can be retained, transformed, repaired or given another life.
That applies at the scale of buildings, but also to objects. We are interested in longevity not simply as durability, but as attachment — why we choose to keep certain things, why some spaces become more valuable to us with time and how design can allow for that relationship to develop.
Ultimately, we are still exploring how architecture can be precise without becoming rigid, how materials can carry memory, and how spaces and objects can continue to reveal themselves through use rather than being fully understood at first glance.