Designing Finland’s tallest timber building


Juha-Pekka Smolander

Director, Structural Engineering, Finland
T: +358 40 708 5386

An innovative new office building, called Keilaniemen Portti, will be Finland’s tallest timber building. Ramboll is on board as engineering partner, to help Varma Mutual Pension Insurance Company realise the ambition of creating an innovative and sustainable structure with low environmental impact.

Keilaniemen Portti, which means “the gate of Keilaniemi”, will be located in the fast-developing business district Keilaniemi in Espoo, Finland, which is home to many of Finland’s largest corporations and known for its many high-rises.

At 60 metres, Keilaniemen Portti will be the tallest timber building in Finland – and one of the tallest timber office buildings in the world – and add another striking high-rise to Espoo’s city skyline.

The 17,900 m2 building will house a number of attractive office spaces as well as a conference centre and auditorium, a restaurant, a sauna, a scenic rooftop terrace and underground parking spaces.

Ramboll is helping Varma realise the ambitious project by providing structural design, geotechnical design and HVAC services as well as designing the energy system and securing BREEAM Certification for the building, aiming for a rating of ‘Excellent’.

Lowering the carbon footprint

Varma’s ambition for Keilaniemen Portti is to create an innovative structure with low environmental impact and eco-friendly materials, and choosing timber as one of the primary building materials is a key part of realising this ambition.

As timber has less than half the embodied carbon of concrete and the ability for long-term carbon storage, timber significantly reduces the carbon footprint of the building.

Moreover, timber is lighter and enables more prefabrication, which can help reduce the number of deliveries to site and result in cleaner siteworks, fewer onsite construction workers and minimised waste on site.

Together with the choice of timber, solar panels, a green roof and energy efficient building solutions will help increase the sustainability of the building.

Unique architecture and innovative technical solutions

Timber is also at the core of the architectural vision. Combined with the sloping green roof, an organic shape with soft curves, and the seaside location, timber will help bring a sense of nature to the office space, with the aim to improve well-being for the tenants. 

However, the complex shape of the building sets high demands for the structural design. 

To meet the demands, Ramboll designed a true hybrid structure that utilises both timber, steel and concrete. 

The building’s stairwells and elevator shafts are made of concrete, while the shell of the building is timber. Together with the surface casting, the steel beams and CLT panels form a composite structure that enables the smooth and free installation of the building systems. The overall thickness of the intermediate floor was minimized and streamlined in the design to enable maximum utilization of the floor height.

In this design process, the Ramboll team developed an innovative new technical solution that connects the timber, concrete and steel structures together, allowing them to work together as one and efficiently transfer loads to the foundation and the concrete shafts. The new solution and connectors have been designed to improve safety during installation and to enable quick and safe construction.

As a result of the innovative framework and intermediate flooring, the floor height is lower than with the traditional beam structure. The lower floor height helps reduce the building’s volume of air to be heated and therefore impacts the building’s energy consumption. Additionally, the lower floor height increases the leasable area to a certain extent. 

The result is a structure that utilises the strength of each material to successfully and efficiently realise the architectural vision. 

Work on the building foundation and underground parking is planned to begin in 2021, and the building will be completed in 2024.

Ramboll Group A/S

Ramboll Group A/S
Hannemanns Allé 53
DK-2300 Copenhagen S
Tel:+45 5161 1000
Fax:+45 5161 1001

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