Infilling in Germany. Estimating the extent of infilling in German municipalities between 1979 and 2011

To achieve the German government's 30-hectare land take per day target, infilling is considered a key planning guideline. However, there are hardly any valid empirical results on the extent of residential construction activity realised as infilling. This is due, on the one hand, to the fuzziness of what constitutes an inner urban area as a spatial construct in German law and planning practice and, on the other hand, to the lack of small-scale data on construction activity. This paper presents a methodology – based on the open data of the Global Human Settlement Layer (GHSL) and the 2011 German Census – to determine and assess for the first time the relevance of infilling at a nationwide level over a period of more than 30 years. The methodology is applied to the 9.409.547 new housing units built in Germany between 1979 and 2011. The result shows a positive trend, indicating that German cities have succeeded over the course of time in boosting infilling. At the same time, major differences between urban and rural areas become apparent, with urban and more central regions being more successful in directing residential construction activity towards existing settlements and already-developed areas. Therefore, a key recommendation is to encourage and support especially smaller municipalities in their infilling efforts.