The Hopealaakso kindergarten building was completed in 2021. Inside the timber-and-steel frame there are daycare places for 210 children.
The project was won with co-operation
The project began with a competitive “design and build” tendering organized by the city of Helsinki, the developer of the kindergarten. The winner was a group of companies consisting of Puurakentajat Oy Group, Rakennuspartio Oy and AFKS / Architects Frondelius + Keppo + Salmenperä.
Janne Manninen from Wood Expert Oy, who was the project manager for Puurakentajat, explains that the winner was resolved with a points system, in which one half of the points came from the estimated costs and the other half from different quality criteria such as the architecture and environmental aspects.
Frame materials were not defined in the invitation for tenders, and therefore all participants were free to suggest a frame of their choice.
- We found out afterwards that out of the participants that made it into the final four, we were the only one that suggested a timber frame. We presume that a timber frame wasn’t more expensive than concrete, even with the required weather protection, which was also included in the plans and costs, Manninen tells.
What’s special about building with timber?
Jyrki Huttunen, the CEO of Puurakentajat Group tells that in Finland weather protection is required for timber, but not for other materials. At the Hopealaakso worksite, the protection was in place for five months – until the building was literally weather-proof.
- Using CLT makes building without weather protection possible because there are no insulation structures that are weather sensitive. We have built bigger projects without weather protection, Huttunen says.
Massive timber projects often aim at leaving as much timber visible as possible, because it adds to the pleasant ambiance of the building. The same applies for Hopealaakso kindergarten, where the comfort of staff and children has been invested in. The street-side façade of the building was coated with zinc plates and the courtyard side with larch.
The benefits of a timber-and-steel frame
According to Manninen, long spans and slim floors were desired for the frame. Therefore DELTABEAM® Composite Beams were a clear choice.
- In this project, using DELTABEAM® meant that the full-sized CLT-elements worked as walls that covered the height of the whole floor. Therefore, we were able to keep the number of elements and joints low, Manninen says.
Huttunen says that the material combination chosen for the frame was great from the builders’ perspective, as it didn’t add anything extra into the building process. Using steel beams also enable building without weather protection.
- When erecting the frame, the beams were mounted on top of the walls and fastened with bolts. Had we used timber beams, HVAC installations would have had considerably less space, Huttunen continues.
Kindergartens have specific needs for sound insulation between floors. A timber-concrete floor meets the needs perfectly, while remaining an all-around simple structure.
Huttunen says that the kindergarten project was the first project in which Puurakentajat used DELTABEAM® Composite Beams. Designing was so good and thorough, that there were no problems with installations. He sees that both CLT elements and DELTABEAM® are similar products that require good planning and designing before delivery to worksite.
- That’s probably why the installing is easy at the worksite – the HVAC demands have already been taken into account, he thanks.
A more sustainable choice
According to Manninen, environmental issues are nowadays on everyone’s radar. In Finland, in addition to a healthy indoor climate, sustainability is an important reason to pick timber as construction material. It seems that lowering the carbon footprint is becoming more and more important, which makes DELTABEAM® Green the best choice for future projects.
Huttunen and Manninen were also involved in the building of Pakila Educational Centre and Verkkosaari kindergarten, both in Helsinki, Finland. Both projects employ the same concept – a timber frame with DELTABEAM® Composite Beams.
Architect: Arkkitehtitoimisto AFKS
Developer: City of Helsinki KYMP/RYA
Construction company: Oy Rakennuspartio
Timber frame construction: Puurakentajat Rakennus Oy
Project size: 2150 m2
Delivery year: 2020
Completion year: 2021