Located at the highest point of the green belt around Brussels, C MIL Building Renovation by Castor Fiber Architecture Studio transforms a former brutalist military building into a contemporary home and office. Defined by raw concrete, a circular plan, and expansive views, the project approaches the structure as a resource to be refined rather than replaced. Its sustainability strategy is rooted in adaptive reuse, using the building’s inherited form, material character, and structural logic as the basis for a new domestic and working environment.
Reuse through subtraction
Strict zoning regulations prohibited extension, leading to a design strategy based on subtraction rather than addition. Under the principle of ‘to create is to delete’, the project removes non-load-bearing interior walls to open the plan and recover the spatial potential of the circular structure. This approach reduces material consumption and avoids the environmental cost of demolition and new construction. By working within the existing envelope, the project preserves embodied energy.
Envelope performance and material continuity
The renovation improves performance while maintaining the building’s brutalist identity. The exterior is upgraded with insulated external plaster that visually recalls raw concrete, allowing the façade to retain its original character while improving thermal efficiency. Steel-look windows reinforce the industrial language of the building while supporting contemporary standards of comfort and enclosure.
At the base, shou sugi ban charred wood provides a darker, more tactile finish that anchors the building within the surrounding nature reserve. This use of charred timber introduces durability, weather resistance, and a visual transition between the rough exterior setting and the refined interior environment.
Light, landscape, and passive spatial quality
A major intervention occurs on the patio side, where walls are replaced with floor-to-ceiling glazing. This brings daylight deep into the plan and establishes a strong relationship with the central garden. The contrast between the outward-facing façade and the inward-facing glass circle creates two distinct environmental conditions: a protective outer edge facing wild nature and an open interior edge oriented towards a carefully organised courtyard. The circular plan supports continuous movement, clear sightlines, and even daylight distribution. Hidden sliding doors allow spaces to be compartmentalised when needed without compromising openness.
Preserving character while extending life
Inside, original concrete pillars, brickwork, and vaults are retained and softened through an old cement-based paint technique. Utilities are exposed externally, avoiding damage to the existing interior fabric and reinforcing the honest material language of the building.
