Hybrid construction – combination of timber, steel, and concrete in a building frame – did not become popular overnight in Finland. Concrete as the main construction method had been the industry standard for a long time already, thanks to its ease of use, durability, and availability. Timber was mainly used in small family houses. Starting from 2010, timber construction for public buildings was introduced. It was not boasted with hoorays, yet it arose suspicions around fire safety, flexibility, and overall construction methods. The ecological aspect was the only one where timber scored full ten points straight from the beginning. Slowly it started; the first apartment houses with CLT slabs were built around 2013. Municipalities approved timber construction even later – the first Finnish daycare center with CLT was built only in 2018.
Lack of know-how kickstarted innovations
Even if timber was an environmentally friendly material choice, it called for a combination with other materials to increase the building height and to make longer spans. The next natural step was the hybrid construction, but the very beginning was full of question marks. The construction industry did not have standardized methods or connection items for hybrid construction. The uncertainty slowed down the projects significantly and increased reluctancy to adopt the method.
As the ecological aspects started setting tighter requirements for new buildings, the industry was between the rock and the hard place – they needed to find a way to standardize hybrid construction and make it the new black of the sector. Thanks to the industry forerunners – Peikko among them – new innovations quickly came forward to ease and speed up the hybrid construction.
Many good things are learnt by doing. As new hybrid construction projects started, it was extremely important to measure, document and follow them up for the projects to come. Little by little standardized ways of working were established, and the hybrid construction became an accepted and well-known construction method.
Challenges and opportunities
Hybrid construction is best suited for projects that require decreasing CO2 emissions but also have architectural demands that timber only cannot fulfill. Buildings with flexible open space and long spans, such as schools or daycare centers, benefit from using hybrid solutions. Yet, high-rise buildings have a certain regularized height limit to consider, due to fire safety requirements. Furthermore, the moisture control in a hybrid frame still arises questions and calls for standardized best practices.
In timber construction, architects traditionally face the challenge of limited spans; in the hybrid construction projects they can create spaces with the customer need in mind, not the frame limitations. On the other hand, the structural designers benefit from standardized solutions, which speed up their daily work. The constructors enjoy the well-known solutions easy to assemble.
When all the parties in the construction project know from the very beginning what kind of frame structure will be used, it speeds up the project itself significantly.
In the future, hybrid construction will take more foothold in the Nordics, especially in educational and office buildings. Not only that hybrid construction is a very well-suited solution for various projects, but it also tackles several climate issues that we need to address in the future. The standardized products and solutions increase the confidence to make even ambitious projects real.
Janne Manninen, partner at Wood Expert Oy, Finland, is a seasoned expert in the Finnish wood industry. While his career at Stora Enso Oyj, he has been one of the driving forces to reintroduce timber to the Nordic construction sector. Janne has participated in several well-known timber and hybrid construction projects in Finland, such as Wood City constructed by SRV. Thanks to hybrid frame construction and Peikko’s DELTABEAM®, the building’s overall height was reduced for more than one meter, and the amount of columns inside the building were reduced significantly to increase flexibility.