Rear view of a residential building with a timber extension and red accents, surrounded by trees and plants.

A rear view of a renovated residential building featuring a transparent, full-height timber volume with red accents, surrounded by greenery.

Rear view of a residential building with a modern timber extension and red metal stairs.
Modern extension of a brick building with large glass windows and red accents.
Renovated building with modern glass extension and red accents.
Modern extension with large glass windows and red accents on a brick building.
Modern building extension with red metal staircase and large glass windows.
Interior with red spiral staircase and large windows.
Interior view showing a red spiral staircase and a window with a brick wall outside.
Interior view with a red spiral staircase, large wooden-framed windows, circular glass floor inserts, and exposed wooden beams on the ceiling.
Interior with red spiral staircase and large wooden-framed glass doors overlooking a garden.
Interior with large wooden-framed window, red metal railing, and slatted wooden floor.
Room with large sliding glass doors, red metal railing, and radiator.
Interior with large sliding glass doors, red railing, and vertical radiator.
Interior with sliding glass door, red railings, and white radiator.
Modern kitchen interior with red spiral staircase and garden view.
Interior with red steel beam and column, green marble table, and built-in shelf.
Red spiral staircase next to a large window with a view of a brick wall and greenery.
Scale model of a building facade with open spaces, green railings, and an outdoor area with a white lounge chair and red table.
Modern house extension with glass windows and red framework surrounded by greenery.
Interior of a living space with large windows leading to a balcony, featuring a red chair, patterned rug, bookshelf, and a person standing by the balcony.
Interior view with wooden floor and ceiling, red metal railings, and large windows showing greenery outside.
Drawing of a building facade with a transparent timber volume and large sliding windows.
Floor plan with spiral staircase, kitchen, dining area, and rooms.
Section drawing of a building with multiple floors, depicting interior spaces, staircases, and structural components.

Story

Revitalizing a 1941 Residence with a Transparent Timber Volume

Located near the Koekelberg Basilica in Brussels, BELVEDERE transforms a 1941 residence by redefining its relationship with the south-facing garden. The intervention introduces a transparent, full-height timber volume at the rear, historically a raw, utilitarian facade. This architectural addition serves as a multi-functional filter, acting as a circulation core, a winter garden, and an extension of the living zones.

The program is reimagined as an atypical vertical stack, with the kitchen, dining, and living spaces oriented toward the exterior. The sous-sol is activated, transformed into a garden-level guest suite and office. The tectonic approach emphasizes a lightweight, dry-assembly construction logic. The extension's floors utilize slender steel beams and permeable wooden structures—a perforated CLT panel on the ground floor and timber lattice work above—dissolving the visual boundary between levels while minimizing structural load.

Defined by a stack of expansive sliding windows in FSC-certified timber frames, the façade can be completely retracted, transforming the glazed volume into open-air terraces. The project champions transformation through subtle addition rather than demolition. By preserving the existing masonry shell and grafting this lightweight structure onto the rear, the design minimizes waste and respects the embodied energy of the original construction. This approach embodies a durable, circular ethos, extending the building’s lifecycle and adapting it to contemporary living standards without the heavy environmental cost of extensive reconstruction.

  • Transparent, full-height timber volume

  • Multi-functional filter: circulation core, winter garden, living extension

  • Atypical vertical stack of spaces

  • Lightweight, dry-assembly construction

  • Retractable façade for open-air terraces

Detail Description
Location Brussels, Belgium
Architect ALTSTADT
Year of Completion 2026
Main Material Timber, Steel, CLT
Environmental Focus Circular ethos, minimal waste

Technical Summary

Finishes

  • Exterior: Transparent, full-height timber volume with large sliding windows and red metal accents.
  • Interior: Wooden floors with circular glass inserts and exposed wooden beams on the ceiling.

Materials

  • Timber — Used for the full-height volume and window frames.
  • Glass — Large sliding windows and doors.
  • Metal — Red metal stairs and railings.

Construction / Systems

  • Lightweight, dry-assembly: Utilizes slender steel beams and permeable wooden structures.

Products

  • Not specified

Palette / Lighting

  • Colors: Red, Natural wood tones
  • Lighting: Bright and airy with large windows allowing natural light.

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