LoLaRE

LoLaRE – Long-Lasting Real Estate (LoLaRE)
Research into the causes for early demolition of buildings 

Prof. Dr.-Ing. Dipl.-Wirt-Ing. Jens Otto, Dipl.-Ing. Charlotte Dorn 

© IBBW

Why are buildings currently being demolished even though they are still usable?

This question was investigated by evaluating a large amount of data from the Federal Statistical Office on the demolition of buildings, as well as through discussions on this topic with a large number of planners, builders, construction companies and authorities. As a result, conclusions were drawn from the mistakes of the past so that they would not be repeated in the planning of future construction projects. This contributes to new buildings being usable for longer. 

The building stock in Germany is subject to a continuous process of change. When existing forms of use no longer work, demolition and subsequent new construction are often chosen. This approach can be intensified in cities due to limited space, but it contradicts the climate targets of the Climate Protection Plan 2050. Premature demolition destroys bound resources and grey energy and causes additional emissions from new construction. Thus, a shortened service life of buildings jeopardises both climate protection and resource efficiency goals. At the same time, relevant data on building demolition has so far only been recorded superficially. Motives or decision-making processes are hardly documented statistically. A comprehensive understanding of the interrelationships is lacking.

The LoLaRE research project investigates the causes of building demolition from the perspective of key decision-makers. The aim is to extend the useful life of buildings by means of a practical assessment tool. The analysis is conducted from an economic, ecological and sociological perspective in order to systematically identify and evaluate factors for durable buildings. 

The evaluation of statistical data on building disposals between 2007 and 2021 shows:

•     Building disposals decreased by 26.3% (residential buildings more than non-residential buildings).
•     Early demolitions are significant: 17.3% of residential buildings are demolished before reaching their potential lifespan (≤ 42 years).
• Private owners are playing an increasingly important role.
• Geographically, demolitions are concentrated in North Rhine-Westphalia, Hesse, Baden-Württemberg and Bavaria.
• The most common reason is the construction of a new residential building on the same site.

However, statistical surveys provide little depth of explanation; qualitative reasons for demolition beyond the continued use of the land remain unclear. To fill these gaps, a supplementary expert survey provides a deeper understanding of the reasons behind decisions. It became clear that legal and normative frameworks often have an indirect effect, but intervene massively in the decision-making process. Examples of this are monument protection, which prioritises the preservation of existing buildings, or building regulations that favour demolition due to higher utilisation potential. Economic considerations play an equally important role: high renovation and pollutant disposal costs, increasing investment requirements for modernisation and stricter standards, particularly in fire protection, can lead to the renovation of an existing building being classified as uneconomical. Structural and technical aspects relate in particular to load-bearing capacity, existing load reserves, load-bearing structures and room and building proportions. If floor heights and building depths are insufficient, conversion can be technically difficult or cost-intensive. In addition, structurally relevant components make flexible room configurations difficult, which limits long-term adaptability. Social and cultural factors also play a role: sustainability awareness favours preserving existing buildings, while at the same time a widespread consumerist mentality indirectly supports demolition decisions.

Based on these findings, the research project concludes that flexibility of use is of central importance for long-lasting buildings. Buildings that are designed to be neutral in terms of use from the outset are better able to adapt to changing requirements over their life cycle, thereby avoiding premature demolition. An exemplary evaluation of various planning parameters illustrates these relationships. When the clear room height varies between 2.40 and 4.50 metres, it can be seen that the degree of flexibility initially increases with increasing height, but only increases marginally from around 3.00 metres upwards. At the same time, emissions, primary energy requirements and life cycle costs increase with increasing building volume. The optimal range therefore appears to be between 2.75 and 3.00 metres, which allows for a wide range of uses at moderate additional cost. The situation is similar with regard to building depth: as depth increases, emissions and primary energy requirements per usable floor space decrease, as the ratio of envelope area to volume becomes more favourable. The degree of flexibility increases up to a depth of around 13 metres, but then decreases again as certain types of use become functionally restricted. Life cycle costs increase largely linearly with building depth, as area, volume and operating costs increase. Taking into account flexibility, resource efficiency and costs, a building depth of around 13 metres is therefore considered optimal.

The combination of these findings shows that many early building demolitions are less due to a lack of structural integrity and more to insufficient adaptability to new usage requirements. Flexible structures, sufficiently dimensioned room heights and balanced building depths increase the likelihood of long-term usability and reduce demolition risks. Flexibility of use is therefore becoming increasingly important as a planning principle in order to reconcile ecological goals, economic viability and social requirements. At the same time, there is a conflict of objectives between the constantly increasing requirements for new buildings and the limited feasibility of implementing these standards in existing buildings, which can encourage demolition decisions. Normative requirements for existing building conversions are currently insufficient, meaning that planners and owners are often faced with economically disproportionate measures. Political and regulatory strategies that support the preservation and flexible redevelopment of existing buildings are therefore becoming increasingly relevant in promoting a sustainable building and usage culture.

The Long-Lasting Real Estate research project was funded by the Federal Institute for Research on Building, Urban Affairs and Spatial Development (BBSR) on behalf of the Federal Ministry of Housing, Urban Development and Construction (BMWSB) with funds from the Zukunft Bau innovation programme under file number 10.08.18.7-22.16.

The project ran from December 2022 to December 2024.