SIE/HOME 21 fits the latter category. Multifunctional building was therefore a prerequisite for this program. The buildings will provide the city with housing for the first 10 years of their life-cycle, but they must be designed so that they can be economically converted into commercial property after this intial period of usage. This programmatic constraint required a simple, rapid and use-neutral construction. SLIM-BUILDING® (Patent Dr. Winfried Kallinger) answers these needs. This innovative system combines slim steel columns with cast-in-place ferro-concrete floor slabs, generating open, non-directional spaces without cross-beams or load-bearing walls.

Efficient construction is a prerequisite for rapid housing; slim-Building reduces construction time for the building shell by half. Economy of time was also essential for the rentability of the undertaking. The project must be amortized within fifteen years, and therefore construction costs could not exceed €1.200,- /m², which is approximately 20% less than similar housing estates using typical means of construction. These low building costs allow the rents to be set at surprisingly affordable rates: €7,50/m² including maintainance, taxes and partial furnishings.

SIE/HOME 21 optimizes the potential of the SLIM BUILDING® system. The floor plans use a strict, highly-economical grid that functions ideally for both housing units and for future commercial use. The open spaces have ceiling heights of 2,82m and can be flexibly subdivided for a large variety of uses. The initial programming reflects the social concerns of the Rapid Housing Program. The compact yet well-organized apartments are to be rented to low-income tenants, many of which are recent arrivals in Vienna.

In the first floor of the north-west tract is a centre for single-mothers; the groundfloor of the southeast tract houses assisted-living for the elderly. Many of the tenants are recovering from recent bouts of homelessness, and HOME 21 offers them their first apartment after years of living rough. The complex has no cellar and is not built-out below grade. At-grade parking complements the flexibly-subvisible commercial units on the ground floor. The architectural language and the project’s materials reflect the principles of program, building system and economy, and harmonizes the building’s structure with the balconies, the facade and the ground floor usage.

The frame of the balcony system is built out of galvanized steel tubes. Its verticals align with the axes of the SLIM BUILDING® system. The pre-cast balconies are laid upon horizontal consoles, which span between the verticals. The balustrades consist of coil-coated corrogated aluminium in trapezoidal profile. The balconies can be placed upon the galvanized steel consoles in various positions. This generates a rhythmic counterpoint to the order of the structural grid. The play of colour between the red-rendered facade and the gold tones of the balconies lends the architecture both warmth and tension.

Credits: - trans_city TC ZT - Managing Partner - Mark Gilbert - trans_city TC ZT - Lead Architect - Markus Steiner - trans_city TC ZT - Managing Partner - Christian Aulinger