Protected old building stock hidden within ECHA facilities

The new, eight-storey facilities of ECHA, the European Chemicals Agency, were completed in early 2020 in Telakkaranta, Helsinki. The office building accommodating about 600 employees is part of Skanska’s area development project, in which office facilities, commercial premises and coastal urban residential buildings will be constructed near the former Helsinki shipyard and the protected cranes.

“Telakkaranta will become an amazing area, something that you will not see every day,” says Mikko Rantanen, Skanska’s Site Supervisor. Collaboration between the designers and the worksite staff was highlighted in such a high-profile office site, and Rantanen considered it important that the chief structural engineer spent a great deal of time on-site also during the implementation stage. “This site had plenty of challenging frame structures and details that could not be fully conveyed through the drawings alone.”

High quality objectives were set for the office site’s design early on during the project. “All the structural solutions had to support the vision of the winner of the international architecture competition, from the appearance of the site to the usability of the premises,” says Sweco’s Chief Structural Engineer in charge, Anssi Vuorenmaa. As an example, the facade’s corten steel cover gives the building a unique look, especially in the evenings when lights shine through the cladding.

The office building was defined as an exceptionally challenging design site, and the structural engineers went through several work versions together with the architect and the client. “We brainstormed and refined the idea together, creating a solution where the architectonic idea meets a structurally and technically solid implementation,” Vuorenmaa says. He thinks that the team spirit of the project team was exceptionally good. “The challenging nature of this project turned into its strength, creating open trust and the sense that we were in this together.”

Office premises designed over old wood workshop

The ECHA facilities comprise an office building as well as a conference centre joined to it with a connecting bridge. The office part of the building was designed on top of an old wood workshop, which required building new foundations. A hole reaching up to the bedrock was excavated for the basement floor. The building’s location only ten metres away from the seaside brought its own challenges. “The basement had to be sealed to withstand the water pressure, so the water pressure walls and the base slab go around the entire building,” says Vuorenmaa. The building has also been prepared for a flooding height of up to three metres.

The load-bearing structures were reinforced with eight new composite columns that rise through the entire old building. The WQ steel beams and composite columns bear the loads of all the seven new floors. “On the outside, it might look as if the old building is supporting the loads of the floors above it, but, in actuality, the new part does not place any pressure on the old part’s structures.”

Rantanen from Skanska believes that the most unique feature in the office is the bright lobby area with a glass ceiling in the middle of the building, reaching up to the top floors. “The whole building has been built around this lobby and the open staircase. At the same time, the old building will be hidden inside the new one, and the lobby allows visitors to see one of the old facades.”

As a consequence of this lobby, all office floors are different from each other and the building actually grows narrower towards the top. The top floors have exceptional level structures; protruding edges that had to be suspended with tension rods all the way from the roof. The facade also has a graduated structure. “It took a great deal of detail planning to make the structure watertight,” Vuorenmaa says.

At the users’ request, the office rooms have been separated with easily adaptable system walls. Otherwise, the office only has two main staircases adding rigidity. “The column and beam frame allows building expansive open spaces.”

The conference centre was fitted into a protected engineering workshop

The second part of the office building was the engineering workshop, completed in 1916 and designed by architect Sune Macon, which was transformed into a conference centre. Sweco’s experts were in charge of studying the old structures being renovated and were responsible for their building physics reviews. The facade of the building, valuable to both the city image and building history, has been protected with a local detailed plan, which means that the appearance of the facade could not be changed in connection to the repair work.

The engineering workshop was pared down to its bones. The ground-level concrete floor was removed and the soil mass underneath the building was changed up to bedrock, to a depth of eight metres at its deepest. The base floor and interior structures were also replaced in their entirety. The most awe-inspiring detail of the completed conference centre are the conference halls on the second floor; they are separate from the load-bearing frame and appear as a floating and soundproofed ‘black box’.

“The entry to these halls goes through the connection bridges from the lobby,” Vuorenmaa says. Thanks to the exceptional structural solution, the lobby showcases the history of the building as the engineering workshop of maritime industry while the conference halls ‘floating’ on top of beams take the onlookers’ thoughts forward, to the still unknown, futuristic future.