Description

The roof extension by PPAG Architekten comprises four residential units on top of a building from the late 19th century in the Radetzkystraße in central Vienna. The initiator of the project, which over the course of the project expanded to become a collective custom build project, is a relative of the building’s owner and was able to convince both the owner as well as the public authorities of his idea for an unconventional building project, which lies in the conservation zone where the historical townscape is protected. The individual elements of the roof, all rendered white, form a sculptural constellation that resembles a Tunisian village.

The prescribed roof incline means that they cannot be seen from the street. The four units encompass a total of 396m² and are timber frame constructions in different proportions that respond to the respective functions within. The cuboid blocks, which use only 60% of the possible maximum building volume, vary in height from 2.3 to 5 metres and are made as one- or two-storey elements. Each unit has its own part of the roof terrace, which totals an area of 176m².

The ambitious urban redensification project is reached via a lift inserted into the centre of the stairwell of the old building. At the top of the building, this projects out of the roof as a freestanding element and opens onto a communal terrace from which the individual units are reached. An additional escape stair on the courtyard side leads from the roof to the third floor of the building. Solar collectors on the roof are used to provide warm water heating for the new extension, and the low-energy construction also employs a heat recovery system to minim ise the heating requirement.

The project was initiated by the son of the house owner and a friend, and two further members of the group were recruited from their circle of friends. During the financial crisis – which coincided with the planning phase – the group shrank back to the two initiators. The project continued nonetheless and over the course of its development two further parties joined the group. Planning meetings took place every two weeks and there was an extended planning workshop later in the planning process.

The site is an extension to existing private property.

The project began in 2007 with planning and construction from 2008 to 2012.

Privately financed.

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Originally published in: Annette Becker, Laura Kienbaum, Kristien Ring, Peter Cachola Schmal, Bauen und Wohnen in Gemeinschaft / Building and Living in Communities, Birkhäuser, 2015.