What is the difference between open and closed construction in terms of the usability of a plot of land? (Author: Michael Pitsch) The development plan regulates the structural usability of the property. Based on the example of the Vienna Building Code, this is defined in §5: "The development plans must show whether or in what way the land areas covered by the zoning plans and the rooms above or below them may be built on (...)" An essential part of this regulation concerns the construction method. This determines how the buildings must be arranged on the property. The Vienna Building Code distinguishes between the following construction methods: - Open construction method (o) - Coupled construction method (gk) - Open or coupled construction method (ogk) - Group construction method (gr) - Closed construction method (g) With the open construction method, a lateral boundary distance must be maintained and minimum distances to the building site boundaries must be taken into account. The open construction method also leads to a loose, small-scale development structure with open spaces. In contrast, the closed construction method involves building onto the "side" boundaries, resulting in a continuous façade frontage. One example of closed construction is perimeter block development. As there are nine different building regulations in Austria, the construction methods are also defined and interpreted differently. Lower Austria should be mentioned here as an example. In Lower Austria, for example, a closed development also exists if the development predominantly adjoins the side property boundaries. In the open construction method in Lower Austria, a lateral building width must also be kept free of outbuildings. However, the building utilisation is not only determined by the construction method. The development plan can also define the density by means of a percentage or an area restriction. It can therefore be stated that the construction method is not the only decisive factor for the utilisation capacity. Several aspects must always be considered.