The housing production office at the City of Helsinki, ATT, organised a new kind of Design & Build competition for woodbuilt apartment buildings, to be built in Pukinmäki at Eskolantie. The competition was won by SRV in conjunction with Stora Enso. The proposal also proved to be the most economical one in the competition.
The scheme comprises four apartment and rental flats. The ground floor of each house is of concrete, while the upper floors are all of timber construction.
In terms of townscape, the point of departure for the project was the preliminary town plan for the area. The dice-like point blocks are built along Eskolantie and, as in the preliminary town plan, the blocks are turned in different directions in relation to the buildings surrounding the site. This enlivens the townscape, offers the apartments unrestricted views in different directions and gives them a better aspect. The street elevations are somewhat closed, while on the opposite side, the elevations are open. Balconies act as a buffer zone to prevent too much solar gain.
The number and size of the apartments and their distribution vary on each floor. Different layouts on each floor give a certain liveliness to the elevations, while spatial elements in solid timber are pushed in and out to obtain a relief effect. This is made possible by the complex range of apartment types and series production of the solid-timber spatial elements.
There is a sauna for each building located on the highest floor, each one linked to extensive roof terraces. This is partly because the town plan allows the top floor to have only three-quarters of the permitted building area of each of the other floors.
Parking is located on the site, under canopies covered with plants, to give the residents a more congenial outlook. The idea was to pay paticular attention to planting.
The facades of the buildings are in timber as well as the construction. Wood is also used as a finishing material in some of the interior spaces, for ceilings and floors. The loadbearing and stiffening structure of the buildings is of solid timber elements made of Stora Enson CLT (Cross Laminated Timber). The apartments and balconies are built of spatial elements. Staircases were assembled on site from wall and intermediate floor elements. Roofs were manufactured in the factory in sections and lifted into place on site. Temporary roof elements were used during construction.
The strength and stiffness of CLT provides a sound basis for the manufacture of spatial elements. From the construction angle, stiff boxes allow overhangs and recesses, and a varied layout of apartments on each floor.
Solid timber slabs give the apartments agreeable acoustics, with no echo. Moreover, the double structure that goes with the spatial elements gives good sound insulation between flats. In terms of energy, the development as a whole is of low-energy level.
The spatial elements were assembled and finished in Finland so that they were completely ready for use. Even the facades were attached to the spatial elements at the factory. Industrial prefabrication, protected from the weather, improves the quality of building and moisture control, and speeds up construction. ATT set high standards for moisture- control in the construction. The scheme was a joint pilot project by City of Helsinki building control and ATT, which drew up and tested new guidelines for weather protection and moisture control during construction.