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“The City as a Quarry: Housing Transformation” is a Brussels symposium on 4 November 2026 about finding housing capacity in buildings, structures and materials that already exist. Curated by Marta Peris and José Toral of PERIS+TORAL Arquitectes, the event asks how conversion, rehabilitation, extension and reuse can address both the housing crisis and the climate emergency. It is part of the Government of Catalonia’s “Contemporary Catalan Architecture Conferences: Social Housing” series, held within the framework of World Capital of Architecture Barcelona 2026. The practical idea is simple: before demolishing and extracting more materials, assess the city’s existing building stock as a resource that can be adapted for homes.
What does “the city as a quarry” mean for housing?
The metaphor reverses the usual construction sequence. A quarry supplies stone and other raw materials for new building; a city already contains floor area, foundations, frames, façades, services and components that may be recoverable. Housing transformation starts by asking what can remain and be adapted before treating demolition and new construction as the default.
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When and where is the symposium?
The free event takes place on 4 November 2026, from 09:00 to 13:30 CET, at the Delegation of the Government of Catalonia to the European Union, Rue de la Loi 227, 1040 Brussels, Belgium. The programme lists a Government of Catalonia registration page, but its current availability was not confirmed because the page was inaccessible when the event information was checked.
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| Time | Programme | Participants |
|---|---|---|
| 09:00–09:10 | Opening | Programme session |
| 09:10–10:30 | Policies for Housing Transformation: Scale, Financing and Productive Transition | Elena Montani, New European Bauhaus Unit, Joint Research Centre, European Commission; Tatiana Márquez Uriarte, European Commission Housing Task Force; Josep Casas i Miralles, Deputy Director General of the Generalitat de Catalunya |
| 10:30–11:00 | Break | — |
| 11:00–12:30 | Architectural Transformation: Rehabilitation, Reuse and Extension of Built Heritage | Xavier Bustos Serrat, Cities Connection Project; Frédéric Druot, Frédéric Druot Architecture; Jaime Eizaguirre, Atelier 229 and co-designer of the Brunfaut Tower transformation in Brussels |
| 12:30–13:30 | Closing discussion | José Toral Fernández, moderator of both round tables |
How can converting existing buildings add housing?
Conversion can create homes by changing a building’s use, reorganising its floor plates or adding volume. Office and commercial premises may provide large areas for apartments, while residential renovation can improve layouts, daylight, energy performance and accessibility. Extensions can increase capacity without removing the original structure. Reuse of components can also reduce the quantity of new materials required.
Office and commercial conversion
Teams must establish whether floor depth, window positions, escape routes, floor-to-floor heights, services and fire separation can support homes. A conversion that produces many nominal units but poor daylight, ventilation or accessibility is not a successful housing outcome.
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Residential rehabilitation and extension
Renovating occupied blocks can preserve homes while improving safety and performance. Extensions may add apartments or shared facilities, but they bring structural, planning and construction constraints. Phasing and resident communication become part of the design rather than an afterthought.
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Reuse of structures and components
Keeping a frame, façade or building services can avoid demolition waste and some new-material demand. Reclaimed components require surveys, testing, documentation and a realistic installation plan; reuse is only credible when performance and compliance can be demonstrated.
How does adaptive reuse respond to the housing crisis and climate emergency?
Transformation can increase supply more quickly than assembling an entirely new site, particularly where land is scarce and infrastructure already exists. Retaining construction also has the potential to avoid emissions associated with demolition and new materials. Those benefits must be calculated for each project: an unsuitable structure may require so much reinforcement or reconfiguration that replacement performs better on cost, carbon or housing quality.
The policy programme deliberately joins housing scale, financing and productive transition with architectural practice. That matters because a technically feasible conversion can still fail if planning rules, building codes, funding conditions or affordability requirements prevent delivery.
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What does the “quarry” idea look like beyond buildings?
Manfred Spocter’s study of Cape Town shows why post-extractive places remain part of urban life after extraction ends. The 2023 paper in the South African Geographical Journal mapped 77 quarries; 71 were in a post-extractive state. It found that 35% of disused quarries had not been rehabilitated or altered by human activity after closure, while 65% of post-extractive quarries had been used for housing, commercial, educational, recreational, infill, or agricultural-water functions.
These are Cape Town figures, not measurements of Brussels, Europe’s housing stock or this symposium. Their value is conceptual: sites shaped by extraction can become continuing urban assets, carrying material memory while supporting new uses.
What should architects compare before renovating, extending, reusing or replacing?
A disciplined appraisal should make the trade-offs visible rather than assuming that “reuse” is automatically the answer.
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- Housing yield: count additional homes and usable floor area, including the quality and size of the units.
- Retention: record how much of the structure, envelope and components can remain.
- Carbon and material use: compare avoided demolition and new-material demand using embodied-carbon accounting where data is available.
- Cost and finance: test capital cost, funding model, affordability obligations and long-term operating implications.
- Regulation and heritage: check planning, fire, energy, accessibility and conservation requirements at the outset.
- Delivery risk: allow for survey uncertainty, complex interfaces, phasing and disruption to occupants or neighbouring businesses.
- Social outcome: assess tenure, public benefit, displacement risk and access to transport, schools, services and public space.
Which digital tools support a reuse-first workflow?
Industry commentary on the symposium’s theme points to a practical sequence: reality capture documents the existing building; scan-to-BIM turns that record into a coordinated model; a component inventory identifies what can stay or be recovered; and embodied-carbon assessment compares adaptation with replacement. These tools support decisions, but they do not remove the need for physical inspections, material testing, code review or cost planning.
- Capture existing conditions: combine measured surveys, photographs and reality-capture data, recording uncertainty rather than hiding it.
- Build a coordinated model: map structure, envelope, services, access routes and areas with heritage constraints.
- Inventory components: note condition, dimensions, performance, ownership and recovery requirements for reusable elements.
- Develop alternatives: model rehabilitation, conversion, extension and replacement scenarios against the same housing and compliance brief.
- Compare whole-project impacts: include embodied carbon, finance, programme, disruption and social outcomes, not only construction cost.
Why is policy part of architectural transformation?
The symposium’s two round tables connect public policy, financing, regulation and design because housing delivery depends on all four. A city may have abundant underused floor area but still need changes to zoning, tax treatment, funding rules, technical standards or heritage processes before that capacity becomes affordable housing. Bringing policy officials and architects into the same discussion helps expose those dependencies early.
Frequently Asked Questions
Is “The City as a Quarry” a book or a building project?
No. It is a professional symposium in Brussels, organised within a Government of Catalonia-linked conference series on social housing. Its subject is a method for transforming existing urban assets, not one named development.
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Can every empty office be converted into apartments?
No. Suitability depends on factors such as floor depth, daylight, ventilation, escape routes, floor-to-floor height, services, structure and local code. A feasibility study must establish whether those constraints can be resolved without undermining housing quality or affordability.
Does retaining an existing building always produce lower carbon?
Not necessarily. Retention can avoid demolition and some new-material emissions, but extensive reinforcement, replacement services or complex construction can change the result. A project-specific embodied-carbon assessment is needed to compare realistic options.
What is the relevance of Cape Town’s quarry figures to a Brussels housing symposium?
They are contextual evidence rather than a performance measure for the event. Spocter’s 2023 study demonstrates that post-extractive sites can continue to function as urban resources, supporting the broader idea of reuse and transformation.
Who is the symposium intended for?
The programme is aimed at people working across housing policy, finance, planning, architecture, heritage, construction and ecological transition. Its cross-disciplinary format is designed for decisions that cannot be made by designers alone.
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