Dunes House / HGA Henning Grahn Architektur

Architects: Henning Grahn Architektur
Area: 125 m²
Year: 2025
Photography: David Schreyer
Lead Team: Henning Grahn
Design Team: Henning Grahn Architektur
Engineering & Consulting > Structural: Ahrens Ingenieure
City: Mainz
Country: Germany

Dunes House is a compact residential project in Mainz that demonstrates how constrained urban plots can be transformed into dynamic, sustainable living environments. Designed by Henning Grahn Architektur, the house replaces an uninhabitable semi-detached structure and introduces a timber-based construction system emphasizing prefabrication, efficiency, and material clarity. The design responds directly to the site’s funnel-shaped geometry, creating a dual orientation that connects interior spaces to both a landscaped garden and a more urban access side. Despite its modest footprint, the dwelling accommodates a family of five through a highly efficient layout. The project integrates simplified construction layers, avoids adhesive bonding, and employs durable materials such as pre-greyed larch cladding, reinforcing its ecological and long-term performance ambitions.

We try to simplify elements where possible, as was implemented, for example, in the residential building ‘Dunes’, where the insulated ground slab is directly used as finished floor.
Interview with Henning Grahn of Henning Grahn Architektur

Dune house is set within a heterogeneous residential context; the project engages a mix of post-war housing, single-family homes, and remnants of Gründerzeit architecture. Rather than asserting contrast, the new building aligns itself with the scale and typology of adjacent semi-detached houses, reinforcing the existing urban rhythm. The intervention replaces a deteriorated structure that was no longer viable due to structural damage and health concerns, allowing the site to be reactivated with a contemporary yet contextually grounded solution.

The organization of the house is driven by the unusual, funnel-shaped plot, which generates a plan that expands and contracts in response to site boundaries. This geometry enables a central living space that opens toward two distinct outdoor conditions. On one side, a green garden establishes a private, softer environment, while the opposite side addresses a more urban frontage. This dual orientation enhances spatial flexibility and allows the house to engage its surroundings in multiple ways despite its limited size.

Internally, the dwelling prioritizes efficiency and clarity, accommodating four individual rooms alongside shared living areas within a compact footprint. The layout supports a family of five while maintaining a sense of openness and adaptability. The architectural language is deliberately restrained, with reduced material transitions and a focus on essential elements, reinforcing a sense of cohesion throughout the interior spaces.

Material and construction strategies are central to the project’s identity. The house is realized using a prefabricated timber frame system, significantly reducing construction time and eliminating the need for prolonged on-site processes. The design avoids adhesive bonding wherever possible, favoring reversible and straightforward construction methods. Interior finishes include laminated timber floors topped with carpet tiles and untreated spruce panels that integrate a wall heating system, further simplifying the building’s technical layers.

Externally, the building is wrapped in a ventilated façade of pre-greyed larch, ensuring durability and minimal maintenance over time. The façade composition is carefully coordinated with flush-mounted wooden windows that are subtly offset, echoing patterns found in neighboring buildings. A plinth formed with L-blocks eliminates the need for additional waterproofing, demonstrating a pragmatic approach to detailing. Together, these elements contribute to a cohesive architectural expression that balances contextual sensitivity, construction efficiency, and environmental responsibility.