Housing development PUUERA

The orientation of this five-storey wooden-built apartment block was optimised to meet low-energy targets. The staircase and plant-rooms are on the north side of the building, while the apartments, especially the balconies, face south.

The building stands on a triangular site bounded by Vierumäenraitti, Vääksyntie and the highway to Lahti. The low density surroundings contain low-rise single-family homes and terrace housing. Some industrial buildings and a school are located on the other side of Vierumäenraitti.

The building is of hybrid construction in which large wooden elements are joined to the laminated timber structure of the staircase. The frame is stiffened with panel components. The staircase is in laminated timber, while the lift shaft is in concrete.

The intermediate floors are made up of elements which are 6250 x 2400 mm in size. The laminated-timber framed elements and the concrete slab on top of them, joined with head­less screws, together form a composite structure. There are no load-bearing walls inside the apartments. The balconies are supported on 215 x 215 mm laminated timber columns. The end-walls and cross-walls are faced with plywood. The white beams and roof joists stand out against the dark cladding.

External cladding is in 28 mm boarding. The firebreak in the ventilation space is a ‘flame trap’ made up of perforated sheet metal. The board width is adjusted to suit the size of the windows to give a whole board width above and below the window. Ground-floor cladding is in narrow grooved horizontal boarding and painted external-grade ply.

The dimensioning of the boarding, the constructional de­tails and the industrial manufacture of the components were optimised to provide a standard construction system. Load-bearing external and cross-walls, roof slab and intermediate floor slabs were delivered to site as ready-to-fix components complete with weather protection.

Using elements on site meant that the number of work stages could be minimised. The whole building was constructed under cover inside a tent. Working in dry conditions and using jacks speeded up installation of the elements.

The plant rooms for each of the flats are located against the external wall of the staircase. Fresh air is introduced directly through the external walls and return air is also expelled through the walls. The ducts leading to the flats are fire-proofed. Heat energy for this passive energy building is supplied by district heating run on wood chips.

Finnish Wood Award 2012