The soil is a valuable resource for humans, animals and plants. However, through progressive land use, urban sprawl and soil sealing this resource is increasingly consumed. Therefore, an important task of spatial planning, confirmed by the objectives formulated in the spatial planning laws, is a sustainable settlement development.The aim of this work is to design a GIS-based analysis for identifying existing potentials of building land, demonstrated using the municipality of Feldkirch in Vorarlberg (Austria) as an example. Since 2001, the Government of Vorarlberg regularly conducts an analysis - called 'Bauflächenreservenerhebung' - to survey both the built-up and not built-up areas. The results therefore are two dimensional. Whereas the 'Bauflächenpotentialanalyse', designed in this paper, calculates the potential construction volume of built-up and not built-up building land. Hence, the output is three-dimensional, which is calculated by comparing the existing development with the maximum legal planning utilization. If all required data are present in its necessary quality, statistical surveys and spatial localizations can be created with minimum effort. The possibilities of visualization include tables, charts, maps and even 3D models. Using only this analysis, doesn't provide a sufficient foundation for making decisions where to undertake explicit actions. This is shown by the detailed examination of three selected focuses. This method can rather be used as a basis and support for further examinations, which can then lead to a sustainable spatial and settlement development. This work can also be seen as a guide to imitate the 'Bauflächenpotentialanalyse', since the necessary steps in a GIS program, the required data and their possible sources of error were described in detail.