The first 6-storey wooden apartment building was completed in the Penttilä district in Joensuu in spring 2017. It was built by the Joensuun Pihapetäjä housing company, owned by the Foundation for the Promotion of Karelian Culture. The Foundation wants to accelerate wood construction in partnership with Karelia University of Applied Sciences and the University of Eastern Finland.
According to the project's own website, the competitiveness of wood construction is based on industrial prefabrication, which can help improve dimensional accuracy and modifiability and control the quality of construction. Industrialised construction significantly reduces construction time and site costs compared to traditional construction.
The main designer of the project is architect Anssi Lassila of OOPEAA, who has been awarded the Finlandia Prize for Architecture. The project architect is Juha Pakkala. The main contractor is Rakennustoimisto Eero Reijonen Oy.
'Joensuun Pihapetäjä consists of 40 rental apartments, and it's building system is a space element with a solid timber CLT building board as the load-bearing frame. The body of the ground floor, which lies partially underground in a slope, is made of concrete,' says Petteri Elonen, construction engineer of Joensuun Pihapetäjä.
The space elements were supplied by Pyhännän Rakennustuote Oy and manufactured at the company's Hartola factory. Fire protection was only needed for the first two floors.
'The facades were built from exterior cladding panels, which had been fire-protected and once painted with Tikkurila's Ultra Pro by Siparila Oy. The second topcoat was done at the element factory with an application amount of 110 g/m²,' says Tapani Toivonen, Production Engineer at Pyhännän Rakennustuote.
The building site started in August 2016, when the first castings were made. The ground floor was made on site. Already in November, the installation of space elements started. The studios and three-room apartments consist of two modules that are connected to each other on site. The installation took place under the protection of temporary roof elements.
'The elements were brought to Joensuu by lorry as special transportations and lifted in place with a 220
tonne mobile crane. The goal was to install one floor per week, and we more or less stayed on schedule,' Petteri Elonen continues.
'The last installations were made in week 2, after which the construction of corridors, roofing, etc. started. Finishing work such as patch-up painting was delayed due to prolonged frost.
Certified fire-protection painting
Fontefire WF is a water-borne fire-retardant coating that expands in heat and forms an insulating foam layer, and its properties are optimised for industrial surface treatment. The paint has been certified by an external authorized research institute with the highest fire-resistance rating B-s1,d0 for wooden products.
The exterior cladding panels of Joensuun Pihapetäjä were painted with fire-retardant coating and primed at Siparila's Vaajakoski factory.
'The panels made of pre-dried planed boards were painted throughout with Fontefire WF. The application amount of 350 g/m² corresponds to 130 µm dry film. Next, the front face and edges of the panels were treated with Ultra Pro topcoat at an application amount of 100 g/m²,' Olli Prättälä, Sales Director, Finland, describes the process.
Siparila is one of the first companies in Finland to receive CE marking authorisation for fire-protected exterior cladding. It has incorporated Tikkurila's Fontefire WF fire protection painting as part of its own fire protection coating systems. This ensures that the fire protection painting is done with officially approved products, under controlled conditions and with high quality.
Text: Arja Schadewitz, Tmi Editrix
Image: Mikko Matveinen
Further information: www.joensuunpihapetaja.fi