Wood City’s newest office combines wood, concrete and steel in a unique way

SRV’s masterpiece of wood construction, the Wood City block, will be completed during 2024. The design of WithSecure’s head office utilised Sweco’s experience from previous projects in the block and brought out the best in different materials.

Wood City Office 2, to be completed in 2024, will complete SRV’s wooden city block in Jätkäsaari, Helsinki. Sweco has been involved in the planning of the block for more than 10 years, which is why SRV set the designers greater overall responsibilities than usual also in the modern head office of the Cyber Security company WithSecure.

“We definitely benefited from the know-how and experience-based solution proposals accumulated by Sweco’s designers,” says Santeri Takala, Head of SRV’s Technical Office.

A new kind of structural system optimises the amount of wood

The hybrid frame office building uses a new kind of frame system that combines the best aspects of different building materials into a functional whole.

“Building is supported by glulam columns. The floor of the building is a composite structure consisting of steel beams and cross-laminated timber (CLT) slabs with a concrete topping,” says Juho Nurmi, Sweco’s Department Manager of Structural Engineering.

Approximately 1200 cubic metres of wood has been utilised in the frame of the office building, which has clearly reduced the carbon and environmental footprint of the office. The goal is LEED Platinum environmental certification and energy class A. Renewable energy comes from solar panels.

“We have designed versatile energy measurements for the site, and strict limits have been set for outdoor lighting, i.e. light pollution, for example,” says Siinto Kangas, Sweco’s Electrical Design Project Manager. In addition, there will be charging points for electric cars in the parking facilities.

The concept of the wooden façade was developed further

In addition to the hybrid frame, Sweco’s previous experience was needed in designing facades made of wooden elements in an office building. The concept evolved from Wood City’s first office location, Supercell’s headquarters. Instead of steel, the façade system is made of lightweight wooden frame elements.

“The solution is functional and safe, even though the wind and rain conditions in Jätkäsaari are harsh,” Nurmi says. “It required solid building physics design expertise from us.”

A successful outcome is ensured by an inspection process in which the structural designer conducts continuous inspections of critical points and model performances on site. In addition, the facades are inspected by a third party appointed by the Building Control Authority. “Our cooperation with Ramboll’s inspectors has worked smoothly, and the construction site has progressed on schedule,” Nurmi says.

Flexible and comfortable working conditions

The joint development work of SRV and Sweco is reflected in the renewed floor structure of the office. A clever combination of concrete, steel and wood structures resulted in a low intermediate floor, which optimised the overall height of the building. “Frame structures take up relatively little space, which enables flexible working conditions for WithSecure,” says Nurmi.

In electrical engineering, conversion flexibility was invested in by choosing a solution familiar from Central Europe: installation flooring. Compared to implementing the cable paths as overhead distribution, for example with socket poles, electricity is now discreetly available at certain intervals. “The premises can also be easily divided into smaller tenant areas,” Kangas explains.

Comfortable and refreshing working conditions are ensured with the DALI-controlled tunable white lighting solution (TW). Human-centric lighting adjusts according to the amount of daylight, among other things. “The lighting is cooler in the mornings in terms of color temperature, which increases the level of alertness and becomes warmer as the day progresses,” Kangas says.