The new secondary school in Pakilanpuisto is an ode to plastic-free solid wood construction

New construction in Pakilanpuisto trusts in solid wood. A new secondary school with more than 1,500 cubic metres of solid wood in its structures was built next to the renovated primary school on Halkosuontie. In the future, more than 1,000 children and teens will be running around the Pakilanpuisto area.

In summer 2022, a new secondary school was completed along Halkosuontie in Länsi-Pakila, next to the renovated primary school. Puurakentajat Group was in charge of supplying the product elements of the new wooden school frame of Pakilanpuisto. The company implements cost-effective and carbon-neutral solid wood buildings with equally solid expertise and professional pride. Sweco was responsible for designing the product elements of the wooden frame.

“By now, our working methods fit well together, ensuring that everything works smoothly,” says Jyrki Huttunen, a Work Manager of Puurakentajat Rakennus Oy. He gives the Project Manager Susanna Friman a special nod of acknowledgment. “Usually we have to keep an eye on the project to make sure that we achieve what we promise, but we never need to keep an eye on Suski. She manages projects so reliably that we have nothing to worry about.”

The wooden construction in Pakilanpuisto also supports the City of Helsinki’s carbon neutrality goal, and Huttunen also believes that solid wood construction is a great way to build schools and daycare centres: no plastic is needed for the frame structures. “The important thing in schools is to use functional structures that promote the children’s wellbeing in the premises.”

Load-bearing and elegant solid wood

The wooden school in Pakilanpuisto has combined traditional school construction with understated and elegant architecture. The school has been made almost entirely out of wood, roof elements included. The structural system of the wooden frame is a combination of load-bearing walls and timber frames.

“The vertical structures are made of CLT board and glued laminated timber, and horizontal structures are made with CLT slabs and load-bearing deltabeams,” says Friman from Sweco. Rigidity was ensured with CLT walls, cantilever columns and slab-like level structures. “Only the foundation and base floor are made out of concrete, and the exterior walls have a brick cladding. We have used more than 1,500 cubic metres of timber.”

Using bricks as the cladding material connects the new building to the renovated primary school.The buildings are also connected by a light, elegant corridor with glass walls. According to Friman, fixed partition walls were only needed for the school’s stage structure and the kitchen. Elsewhere, the premises are open and adaptable. The two-storey-high lobby area is one of the most impressive places in the new building. “It is built on beautiful wooden A-frames with a steel tension rod as their bottom chord.”

Problem-solving needed for the ventilation of the three side-by-side gable roofs

The Pakilanpuisto school features three side-by-side “ships” that all have gable roofs. “The extensive need for weather-proofing was one challenging aspect, as one side of these three sections of the school was built first, then the other side, and finally the middle section was built under a fixed weather guard,” Huttunen says. The last part was built by backing out of the weather guard.

The middle gable roof is closely flanked by the other two gable roofs, so ensuring the roof’s water removal and ventilation proved to be challenging. “We carefully considered the moisture technical factors and building physics engineering of the roof, and designing the wooden roof elements was also an exceptionally challenging task,” Friman admits.

The attic has so many building services pipelines that the load-bearing direction of the roof structure had to be switched mid-way through. “Some of the roof elements are now bearing from the top of the roof and in the direction of the pitched roof area on top of the exterior wall, but the load-bearing beam lines have been switched the other way round at the other end, where elements bear the load against the pitched roof area.”

Structural solutions were refined together

Even the most complex matters were solved in cooperation between the project’s main structural engineer Ideastructura, Puurakentajat and Sweco. “We all had a similar view of the site’s requirement and quality level, which made it easy to agree on all aspects,” Friman says.

She also feels that the design management of this alliance project worked very well, and regular weekly meetings and schedule monitoring ensured that the whole project was tightly under control. “Thanks to this, the work on site also progressed smoothly without any major surprises or hiccups on the way.”

The new school building on Halkosuontie was commissioned in spring 2022. The same building also provides premises to a youth centre, and the school is open to the local residents for many various activities in the evenings and on holidays. The main contractor NCC will continue developing the Pakilanpuisto area through a daycare centre built on Elontie. At the end of the project, more than 1,000 children and teens will be running around the school centre’s area.

Pictures: Arkkitehdit Frondelius+Keppo+Salmenperä ja Arkkitehdit Rudanko+Kankkunen