This four-storey residential building at Länsiranta in Porvoo is one of a row of wooden-clad apartment blocks on a street named Mauno Eerikinpojankatu. It is located at a bend in the road, which allows unusual plan forms even in the smallest flats. The loadbearing structure of the building is in concrete, but it is clad in wood.
The use of wooden cladding called for sprinklers in the interiors and on the elevations. However, while the building was on the drawing-board, Puuinfo commissioned a report on the use of wood for cladding in the context of renovations to blocks of flats. The study showed that the cladding is not of fundamental impor-tance in the spread of fire.
On the basis of this report and on calculations and reports by fire experts, the building owner applied for exemption from the sprinkler requirement, and the Ministry of the Environment gave its permission to omit the automatic fire-extinguishing system.
The concrete structure is supplemented with wooden balconies where the vertical structure is four-storey high laminated-timber columns. The wooden cladding is in 28 mm fine-sawn T&G boarding and exterior grade plywood. The ventilation gap behind the cladding is interrupted at each floor level with perforated steel profiles to prevent the possible spread of fire. The elevations are mainly treated with red-ochre paint.