Kulma21, Helsinki | Structural design of a complex adaptive reuse project

Located in the heart of Helsinki, the KY building has undergone a full modernization. Now named Kulma21, it offers flexible office space to meet evolving business needs. WSP provided structural and layout design for this complex renovation project.

Kulma21 (Corner21) showcases how we can create exciting new places using the buildings we already have – while preserving their history and cultural significance. Built in 1941, the former KY Building has been home to the Finnish president Martti Ahtisaari and the Helsinki School of Economics student union. Now it’s been transformed into a sustainable, contemporary workplace focused on wellbeing, with many unique features restored to their earlier glory.

As the structural designer, our team in Finland played a significant role in the adaptive reuse project – one of the first in the country to achieve BREEAM Excellent with a carbon emission impact 44% lower than a similar new construction.

Kulma 21’s façade has been restored to its original appearance and existing structures retained including the foundations, concrete frame, lift and staircase shafts, and external walls. At the same time, building services like lighting, heating and cooling were upgraded and new features added to improve occupants’ quality of life. From a restaurant, café and versatile workspaces bringing people together, to a new top floor with saunas and a rooftop terrace providing stunning views across the city.

Request additional information

Location

Helsinki, Finland

Client

NCC

Project Status

Completed 2023

INDOOR SPACE

8,700m²

LOWER CARBON IMPACT COMPARED TO NEW BUILD

44%

In our life cycle assessment – conducted in accordance with the Finnish Ministry of the Environment’s official calculation guidelines – we compared a major renovation to a newly constructed building of similar size and architectural design. Even over a 50-year assessment period, the carbon footprint of the new building could not be offset, not even with its lower operational energy use. This was a significant factor when we set out to develop Kulma21 to meet future needs.

Ville Laankoski Design Manager, NCC

Ville Laankoski Design Manager, NCC

Transforming old to create new

To create an inspiring workplace, the existing attic was transformed into a new top floor complete with penthouse offices, sauna facilities, a glazed Southern wall for natural daylight, and a roof deck overlooking Kulma21’s historic neighbourhood.

Paulus Hedenstam, WSP Project Manager explained: “We worked closely with the construction company NCC, the architect , and the heating, ventilation and air conditioning (HVAC) contractor to develop a design that would create more floorspace, manage the challenging roof shape and work in harmony with the building’s functionalist architecture.”

By creating a new steel frame for a mansard roof and a load-bearing floor system combining new and old structures, our engineers enabled new building services to be installed, while minimizing the impact on the original plastered façade.

On the lower floors, space was maximized by using compact and efficient building services like centralized exhaust ventilation, while the basement floor was lowered to house a gym, bicycle parking and spaces for socializing.

Harnessing digital to unlock potential

The challenge for our engineers was how to combine new and old structures and create a vibrant, adaptable workplace, while also meeting BREEAM’s criteria for renovation projects.

Kulma21 was designed to be adaptable, allowing it to meet different user needs within predefined parameters, without needing major changes to fixed solutions. Early in the design phase, it was determined how each floor could be divided for up to three different users, alongside potential locations for restrooms and meeting rooms.

NCC’s Ville Laankoski explained: “The building’s floor to ceiling height is significantly lower than in standard new-build designs, and its structural frame is more irregular. After demolition work, the exposed frame was laser-scanned and modelled based on the scan. Without these modern methods, it would not have been possible to integrate new building services or achieve the desired flexibility.”

“We created a digital twin of the building that was updated daily to give everyone shared visibility” added WSP’s Paulus Hedenstam. “That meant we could quickly identify any issues and develop technical solutions to integrate new structures and building services within the existing frame and make the most of the available space. We also included neighbouring buildings, access routes and traffic arrangements in the model, to help manage the tight, city-centre construction site.”

BIM technologies were instrumental in the project’s sustainable approach to renovation – with Kulma21 recognized in the Tekla BIM Award competition for its pioneering use of information modelling. For example, continuous collaboration with MEP designers, Granlund Oy, enabled our engineers to retain as many of the original beams as possible, while simplifying the installation of modern ductwork and shafts. The size of ventilation ductwork has tripled since Kulma21 was originally built, so the ability to precisely model building services before fitting proved invaluable.

Meet the Visioneers

Juha-Pekka Smolander, Sector Director, Building and Industry at WSP in Finland believes Kulma21 will inspire more adaptive reuse projects in his country and beyond.

"In Helsinki, empty premises account for around a million square metres of unused floorspace, and it’s a similar story in cities around the world. Kulma21 is a great example of how existing buildings can be reused to create thriving new spaces, while preserving their unique historic and cultural identity.”