Anssi Lassila, head designer at Puukuokka, wanted to add some flair to the building’s exterior. Lassila is an architect and believes environmentally-friendly solutions and new technology can be combined to increase quality of life. From the window, you can see the forests from several angles and with Siparila wood siding, the apartment building can blend into the natural landscape.
Puukuokka is the first eight-storey apartment building in Finland to be constructed entirely from wood. Prefabricated cross-laminated timber modules were “plugged in like Lego pieces” to build this architectural work-of-art. In fact, Puukuokka is one of the first high-rises in the world to be built using prefabricated cross-laminated timber (CLT) construction. CLT is an engineered wood made by gluing together layers of lumber, which makes it stronger and more rigid than normal wood. Manufacturer Stora Enso took advantage of these properties to develop a modular building system using only this material.
These lightweight modules provide the building’s main structural framework. Compared to concrete construction, CLT can be installed in half the time and with fewer delays due to weather. This is because CLT keeps the construction time to a minimum as they all come with a finished interior surface and are prepared with fittings so they’re ready to install right away.
Fire safety regulations had previously prohibited buildings of this height being constructed with wood. But a change in Finland’s building code in 2010 – primarily due the fire-resistance of CLT – has made it possible to build an eight-storey building with a wooden frame, as long as the structure is topcoated and an automated sprinkler system is installed.
The exterior of the building is also wooden – large panels clad both the front and rear of the building. The bottom level has been treated with fire retardant to ensure it follows building regulations. The wood siding chosen for Puukuokka is 28mm thick, adding to the durability of the siding. The side facing the road has been painted black, while the courtyard-facing the rear has been left untreated and holds the balconies.