Description

Jyväskylä in central Finland is the location of the first eight-storey apartment building made of wood in Finland, which was completed in late 2014. The fact that such tall residential buildings can even be built of wood is the product of a change in legislation that has simplified fire protection regulations. The project in Puukuokka combines a system of prefabricated volumetric timber modules (CLT = Cross-Laminated Timber) made of spruce with a sprinkler system resulting in a very efficient, material and time-saving system that made it possible to achieve a construction time of just six months. In addition, prefabrication of the modules has resulted in a better degree of precision than is possible with on-site construction, which is influenced by the weather.

The primary structure is based on the Urban Multi-Storey concept by the Finnish-Swedish group Stora Enso. The second largest forestry company in the world, whose headquarters in the centre of Helsinki were designed by Alvar Aalto (1962), is increasingly focusing on using wood as a building material for larger construction projects. Stora Enso is also behind the “Wood City” project in Helsinki’s Jätkäsaari district which also comprises residential and office buildings of up to eight storeys made of wood.

The Puukuokka Housing Block is a pilot project for the CLT-based modular construction method and rests on a base of in-situ cast reinforced concrete that houses communal facilities and the garage. The concrete base and the central hall with its bridge-like CLT elements, which provide access to the apartments, are the only parts of the building constructed on site. Three large window-lined vertical atria at either end and at the bend point of the building where the elevator is located, add spatial variety to the hall, which is characterised by white surfaces and light, warm wood tones. They also serve to naturally illuminate the central hall, which can also be supplemented by a series of tubular fluorescent lights as required. The hall serves not only as the main circulation and communicative backbone of the residential building; its walls also house the vertical supply ducts for heat, water and electricity.

In the apartments – half of which are two-room and half three-room apartments, each with a compact sauna in the bathrooms – the naturally lit interiors are pleasantly bright, which is anything but a matter of course in Scandinavia. Loggias or projecting balconies – the former fully glazed, the latter partially glazed – illuminate the adjoining living rooms and bedrooms, while offering a broad view over the surrounding landscape. The wooden surfaces of the ceilings and parquet floors complement the white walls, which are clad with gypsum plasterboard for design and fire protection reasons.

Like the CLT modules, which are individual stiffened units, the facade elements on the street side are also made of spruce wood, although here they are painted a dark colour. The rearward facades facing the residential courtyard are, by contrast, untreated larch wood, and the irregular pattern of the projecting balconies enlivens the west elevation tremendously. The apartments were marketed using a new type of state-secured lease-purchase model.

Originally published in Bauwelt 29.2015, pp. 20-25, abridged and edited for Building Types online, translated by Julian Reisenberger

---