GAINING BUILDING LAND without expansion - development of single-family housing settlements

Status

completed

Summary

Project relevance

In many of the existing single-family housing settlements dating from the 50's to the 80's there are often considerable potentials for redesignation and infill, which in many cases are not really appreciated and developed. Of particular interest are settlements with housing stock from the post-war and "Wirtschaftswunder"-periods, some of which is already in need of renovation. The resulting infrastructural costs of previous settlement development as well as the change in social structure with its altered forms of households have caused many local authorities to increase their own activities in the housing sector and to support new schemes.

Project aims and scope

The focus is on opportunities for mobilizing existing reserves of land and residential areas in the sense of an "internal development" instead of earmarking new territory for building. Are there such potentials, how big are they and how can they be mobilized?

The project aims to demonstrate empirically that these infill and redesignation potentials within single-family housing structures are not only suitable for creating new residential space but are also capable of providing sustainable economic and social stimuli as well as providing ecological and energetic incentives.

A set of tools, designed to be as easily manageable as possible, had to be developed in order to conduct a comprehensive physical and social evaluation of the existing structures. Demonstrations of model solutions and the preparation of guidelines (a handbook) are intended as support for local authorities in assessing their own structures and in developing and implementing their own infill projects together with the affected property owners. In this process, interest is not centred on optimizing the density of building but, more importantly, on the possible gain of additional households within the stock. Furthermore, the prime concern should not be to obtain an optimum individual solution but to consider an entire housing area.

Three thematically representative local authorities within the land of Salzburg have been selected as case studies. Selecting local authorities of differing topographical situations and regional constraints makes it possible to apply the results to different settlements. After preliminary public relations work, a total of 247 plots (approx. 70 - 100 per village) were scrutinized and assessed. In addition, 49 intensive interviews and 24 counselling sessions were conducted, with a similar number of individual solutions being developed.

Results

Differentiating between internal and external reserves

It has proven useful to make a clear distinction between external (addition of new building structures) and internal (expansion within the building shell) reserves. This was also because of the fact that the internal reserves were often found considerably more frequently than first presumed.

Developing an index for the infill potential

Because of insufficiencies in the existing density calculation models (site occupancy index/GRZ, cubic index/BRZ, floor-space index/GFZ) for achieving a clear survey of the actual infill potential, the infill potential index ("Dichte­potenzialzahl DPZ") was introduced as an approximate formula for calculating volume.

Size of the potentials and reserves

The reserves were recorded per plot with the aid of a registration form and then extrapolated for the entire settlement. Quantitative evaluation (constructional reserves) was then carried out using the infill potential index (DPZ). Qualitative investigations, such as owner questionnaires and surveys of plot structure and construction type, supplemented these calculations. In the settlements examined, the number of additional households determined ranged between 25 - 80 % in the field of "external" reserves. The possible "internal" growth in households was determined as 16 - 42 %. The study therefore shows that, even when the "trend continuation" scenario is retained, considerable reserves of residential space are contained within the areas investigated.

Communication strategy

In this particular project it has been seen that awareness of the problem and the required acceptance and cooperation of the owners can only be acquired on a participatory basis if an attractive offer is made (e.g. neutral planning consultancy). Selected inclusion of the local administration and political representatives (especially the mayor) are also prerequisites for an efficient process.

Sample solutions

A great need for neutral expert advice was observed amongst the owners interested in the project. They also displayed an open attitude to unconventional approaches and higher-level measures affecting the entire settlement.

A key topic during the planning counselling sessions was to solve the contact points between the living areas of the different generations in the context of "multi-generation residences" (exploiting, allocating the open spaces and gardens, lack of barriers). The opportunity for commercial exploitation (office, workshop, apartment rental) also represented a frequent motive in the desire for change.

Handbook

The main product of the research project is a set of "guidelines" (handbook) to enable local authorities to plan, execute and steer projects aimed at the redevelopment of single-family housing settlements. Various different project modules that are described in detail within the handbook can be put together to match the specific situation of the local authority.

Project manager:

DI Paul Schweizer
bautänzer architektennetzwerk Paul Schweizer, Thomas Pletzer OEG

Partners:

• Dr. Raimund Gutmann
  wohnbund:consult
• DI Gerhard Wallner
• DI Helmut Strasser
  SIR (Salzburger Institut für Raumplanung)
• Dr. Franz Hocker
  Salzburger Gemeindeverband
• DI Paul Raspotnig
  Initiative Architektur Salzburg

Co-financing:

Land Salzburg
Abteilung 10 für Wohnbauförderung, DI Helmut Schörghofer

Contact

DI Paul Schweizer
bautänzer architektennetzwerk Paul Schweizer, Thomas Pletzer OEG
Hellbrunner Straße 3/8
A 5020 Salzburg,
Tel.: +43 662 82 77 50
Fax: +43 662 87 21 77
E-Mail: psw@salzburg.co.at