Project Data
Project location
Kaj Frankinkatu, Helsinki, Finland
Completed in 2005
Chronological information
Project design team
Architects Esko Kahri and Petri Viita (Kahri and Co.), Petri Viita, Juhani Väisänen and PlusHome Ltd. project team authors Esko Enkovaara and Timo Taiponen.
Number of dwelling units
77
Project site / building area
site area: 3900 m2 / floor area 6600 m2
Project client
Private developer SATO
Structure type
Steel frame, hollow core slabs + ‘upside- down floor system’
Installation utilities
Horizontal piping installation and piping layout per dwelling is installed in a ‘wet zone’ in an ‘upside- down floor system’, with adaptable electric distribution system in all partition walls.
Infill system/ approach
Clear separation of infill and support. The information system was developed to coordinate inhabitants, designers, client and developers.
Background
In 2002 the second of several technology competitions was organized by the city of Helsinki. The winning PlusHome proposal was developed by architect Esko Kahri (Kahri and Co.) and Tocoman data- cost office with SATO as developer. On that basis, Kahri and Tocoman founded the PlusHome company and together with SATO started a working relationship with a focus on customer orientation and implementation of Open Building principals.
The pilot project is located in the neighborhood of Arabianranta. This new housing area along the seashore was developed starting in 2000. It is located about 5 km (3 miles) from the city center.
PlusHome consists of three decision levels: a building structure and envelope that allows variations of apartment sizes, different layout options within the fixed apartment sizes and a selection of surface materials and fixtures that inhabitants can choose from. The PlusHome concept enables a high degree of dwelling unit variability through technical solutions.
This project consists of one six- and one five- story high building with, at time of sale, 77 for- sale dwellings ranging in size between 39 and 125 m 2 (420– 1345 ft 2). There is an 84 m 2 (904 ft 2) commercial space on the street level, as well as seven street- level workshop spaces for artisans, four of which are connected directly to the dwellings above by internal stairs.
The base building
The structural frame differs from traditional building methods in Finland. Here the load- bearing walls are the longitudinal outer walls, instead of the inner cross- walls dividing the apartment units. This allows a higher degree of longitudinal variation of unit sizes within the support. The outer walls are made of steel frames on which the precast concrete floor slabs bear. Most of the slabs are hollow-core concrete slabs with a 10 m (32.8 ft) span, which is popular in Finland. In the ‘zones’ where wet spaces (bathrooms and kitchens) are considered likely, a special floor design is used in order to allow plumbing to be accessible from the top – i.e. from the spaces served. It uses steel beams with regular holes for horizonal piping, a concrete ‘bottom’ slab providing fire and acoustical separation, and a removable top concrete slab. The hollow- core slabs, steel frame outside walls, vertical piping in staircases and horizontal zones make the basic structure renewable over time An accessible hollow profile at the top of interior non- load- bearing metal- stud/ gypsum board walls allows free placements of electrical and low- voltage wires which run down inside the walls to switches and plugs, allowing easy change or addition of terminations later. The exterior load- bearing steel frames allowed for off- site fabrication in large elements, as well as an almost unlimited option of window placements. Walls between apartments are not load-bearing; they are of light construction with double plasterboards on steel studs. The facades are red brick or clad with thermal plastering; some parts use profiled metal plates. Large balconies for each dwelling, running across the south facade of the building, have shading elements on rollers to allow occupants to freely position them as desired. One innovation was the steel building frame (which received an award from the Finnish Steel Industry Association).
Information / Data Management System
The other main innovation was the information system developed by IT and data consulting company Tocoman, which ensured good management of the added complexity for the project.
The data management system allowed the architect to work on the model, real- time project quantity and cost information and an online internet platform for inhabitants’ use. Residents could choose between alternative floor plans, which were presented in the pre-marketing stage via internet. A wide selection of floor plans was offered, both different apartment sizes and variations within the same size. This stage was open till about 6 months after the construction started. The building would ‘fill- up’ following the sequence of inhabitants’ choices. All the floors became individualized. After that inhabitants had another 3 months to choose surface materials and fixtures while seeing an instant cost estimation of their choices. The buyers could see the change in the total price of their apartment directly after making their choices and could also go back and revise before finally accepting the order. After selections, quantity information was automatically collected and delivered to the contractors. This system allowed smooth implementation on a rather large scale.
Capacity for dwelling variation
The design of the project, supported by the PLUSHOME data management system, enabled residents to choose from a wide selection of unit sizes and layouts as shown in Figures 4 and 5.
