Holzrausch designs Frankfurt penthouse as a "roof garden in the middle of the city"

Munich-based architecture firm Holzrausch has completed a two-storey extension to a penthouse in Frankfurt, featuring open-plan living spaces that connect with a roof terrace overlooking the city.

Robert Volhard, the founder of the architecture and design platform Stylepark, had lived in the building with his wife Patricia for 18 years before moving up a level when the building's roof required urgent replacement.

Two-storey extension within a penthouse in Frankfurt — Holzrausch has completed a two-storey extension to a penthouse in Frankfurt

The couple spotted an opportunity and commissioned Holzrausch to carry out a more comprehensive project that would provide additional space including a kitchen, dining and living area culminating in a full-height opening.

The studio's cofounder Tobias Petri, told Dezeen that the brief was to create "a roof garden in the middle of the city and a bright, open home shaped by unusually precise functional requirements and executed with a characteristically high level of craftsmanship throughout".

Terrace with sliding doors — The brief was to create "a roof garden in the middle of the city"

The Wilhelminian-era building's original mansard roof was replaced with a two-storey extension, which the architects described as a "contemporary crown that complements the historic base while clearly expressing a new spatial logic at the top."

The clients wanted to avoid the sloping ceilings and compartmentalised rooms typical of conventional mansard attics, so the new roof structure instead features vertical walls and a cohesive sequence of open-plan spaces.

Industrial kitchen — Industrial elements are balanced against more natural tones in the kitchen

The reconfigured penthouse totals 400-square-metres across three storeys, with the mansard level accommodating the main living spaces and balcony, while the upper floor houses a home gym and office that opens onto an expansive terrace.

Holzrausch worked closely with the clients to develop the architectural concept and an interior scheme that provides a calm, crafted backdrop for their extensive collection of art and furniture.

Blue-carpeted staircase — One of two staircases features a blue-carpeted approach

"The aim was a distinct shift in atmosphere at the top of the building – 'one lift ride' into openness, light and relaxed, lived-in comfort," Petri added.

The material palette was chosen to create a tactile and refined atmosphere, described by the project team as "arschgemütlich", which translates as "exceptionally cosy."

Wood-lined bedroom — The simple palette is based around materials that will gather patina over time

A key reference was the work of Indian architecture practice Studio Mumbai, which informed the home's warm surfaces, gentle forms and the continuous kambala wood panelling that ties the spaces together.

The simple palette is based around materials that will gather patina over time, including solid wood, terrazzo and brushed stainless steel.

Frankfurt penthouse — Solid wood and brushed stainless steel feature throughout

This approach is particularly evident in the kitchen, where industrial elements are balanced against more natural tones. Utilities, including the ovens, are hidden behind timber fronts to maintain the seamless flow of the units.

Furniture and artworks featured throughout the apartment were drawn from the owners' collection, while the inclusion of bespoke joinery and details such as the partly hand-turned solid wood handles adds to the crafted feel.

A pair of distinctly different staircases connect the three levels, with the blue-carpeted approach stair to the apartment providing a darker, intimate arrival into the main living area.

The upper floor is reached via a sculptural spiral staircase, informed by a similar piece that the client once encountered at a Frankfurt boutique. The staircase winds its way upwards from the kitchen area and is illuminated from above by a large skylight.

Skylight-illuminated staircase — The upper floor is reached via a sculptural spiral staircase illuminated by a skylight

Natural light pours into the extension through openings, including the glazed frontage, creating a strong connection with the roof garden and nearby trees that form a natural screen.

Holzrausch was founded in 1998 by Sven Petzold and Tobias Petri. The company's holistic approach draws on a variety of craft practices, while its own carpentry workshops enable the development of bespoke solutions for residential projects.