TOP HAT!: A Parametric Roof Truss That Gives Old Buildings New Balconies

What if a building's roof could become a machine for generating new outdoor space? TOP HAT! proposes exactly that: a large parametric truss system that sits above an existing residential block and, from its perch, deploys modular balconies, shading devices, screens, and communal areas down across the façade. The project treats the balcony not as a fixed slab cantilevered from a wall, but as a programmable element within a coordinated building-scale infrastructure. It is an argument that retrofit architecture can be systematic without being monotonous.

Designed by Jacob Bodinger and Langdon Drewett, TOP HAT! was recognized as an Editor's Choice entry in the Retro-Fit 2020 competition. The project targets a pervasive condition in dense cities: repetitive residential buildings where individual units have almost no opportunity for personalization or access to outdoor space. Rather than proposing a one-off intervention for a single building, the designers developed a parametric system intended to adapt to different rectangular footprints, making the logic transferable across many sites.

A Variable Hat Truss That Adapts to the Building Below

The project's signature move is the Variable Hat Truss, a large structural framework positioned at roof level. The axonometric diagrams above show two variations of this truss system, each with diagonal bracing and perimeter support frames adjusted to fit different rectangular footprints. This is not one bespoke structure; it is a parametric archetype. The geometry shifts while the organizational logic holds steady, allowing the same family of steel trusses, compression elements, box trusses, translation members, rail systems, and cantilevered corners to reconfigure for each host building.

The truss does more than cap the building structurally. It becomes the operational center of the entire modular system: a platform from which components are stored, moved, and deployed down the façade. This inversion of conventional retrofit thinking, where additions are typically bolted on piecemeal from below, gives the project its conceptual coherence. Everything grows downward from a single coordinated infrastructure.

Crane Rails and Kit-of-Parts Assembly

The exploded axonometric in the first drawing reveals the mechanical ambition behind TOP HAT!. A storage crane rail system runs along the roof structure, enabling modular panels and components to be positioned across the façade without ground-level staging. Labeled structural components clarify how steel members, connection plates, and panel assemblies interlock within a nested modular hierarchy. The second drawing zooms into the wall panel assembly sequence itself, numbering each component and detailing the joinery that allows panels to slot together in a predictable, repeatable process.

This kit-of-parts approach is central to the project's claim of adaptability. Because every element follows a standardized connection logic, residents and building managers could, in theory, reconfigure balcony enclosures, swap shading screens, or add communal spaces over time. The architecture is designed to evolve according to changing users and conditions rather than locking everyone into a single predetermined configuration at the moment of installation.

Light Through Translucent Panels: The Interior Experience

For all its structural ambition, TOP HAT! also attends to atmosphere. The interior corridor view shows what it feels like to inhabit a space framed by the modular system: translucent wall panels filter sunlight into soft, diffuse patterns while the exposed steel truss structure overhead remains legible. The corridor reads as a threshold between the private unit and the new outdoor spaces the system generates. It is a reminder that modularity, when handled with care, does not have to produce cold or anonymous architecture.

A Flexible Roof Plan Over Modular Unit Enclosures

The cutaway axonometric pulls back to show how the full system comes together. Vertical columns rise from the existing building to support individual unit enclosures, which sit beneath the flexible roof plane of the hat truss. The drawing makes visible the spatial gap between the new modular framework and the original building fabric, a gap that accommodates circulation, services, and the movable components that give residents choice over how their balcony space is used.

What the cutaway also reveals is the project's scalar ambition. TOP HAT! is not a single balcony bolted to a wall. It is a second structural system layered over an entire building, one that can host many balconies, screens, social spaces, and shading devices simultaneously. The existing building becomes a datum; the hat truss becomes the generator of everything new.

Why This Project Matters

Retrofit conversations in architecture tend to oscillate between two poles: cosmetic façade upgrades that change very little, and full-scale demolition-and-rebuild strategies that are expensive, wasteful, and disruptive. TOP HAT! carves out a productive middle ground. By introducing a single coordinated structural framework from which diverse components can be deployed, Bodinger and Drewett propose a way to give existing residential buildings new outdoor space, new individuality, and new programmatic flexibility without tearing them down.

The parametric adaptability is what elevates the project beyond a compelling one-liner. Because the hat truss is designed to adjust its geometry to different rectangular footprints, the system positions itself as a transferable strategy rather than a site-specific sculpture. Whether that ambition survives contact with the messy realities of existing building conditions is an open question, but as a provocation about what modular construction could do for the urban balcony, TOP HAT! makes a persuasive case.

View the Full Project

About the Designers

Designers: Jacob Bodinger, Langdon Drewett

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Project credits: TOP HAT! by Jacob Bodinger, Langdon Drewett Retro-Fit 2020 (uni.xyz).