Structural Engineering Between Preservation and Transformation

Existing buildings are increasingly becoming a focus of the construction industry. Resource scarcity, regulatory requirements, climate targets, limited land availability, and economic considerations are driving a growing number of projects that combine new construction with existing structures. For structural engineering, this means balancing the preservation of existing building fabric with the need to meet modern technical standards. 

Framework Conditions for Building Within Existing Structures
A key characteristic of building within existing structures is that existing loadbearing systems are not only preserved but actively integrated into new concepts. This requires careful consideration of numerous framework conditions.
The process begins with analyzing existing documentation, such as load assumptions and construction drawings, where these are available. This is often one of the most critical aspects of structural engineering. For this reason, we place great importance on clear project organization, supported by load plans, positioning plans, and overview drawings.
Existing structures are often not designed for new uses. Questions such as “Does the fire protection concept still meet current requirements?” or “What load capacity do the existing components provide?” must be addressed. Even these fundamental considerations demonstrate that building within existing structures can only succeed through a holistic approach that brings together architecture, structural engineering, and Building Services.

Load Transfer from New to Existing Structures
The basis of every structural design is a clearly defined load path. In existing buildings, this often means that new loads must be transferred through existing structures into the ground. For structural engineering, this requires identifying the potential of the existing structure and making optimum use of often limited space. Examples include adding a timber story to existing supermarkets or replacing outdated construction materials with high–performance products, such as fiber–reinforced concrete bridge decks to strengthen compression zones.
Where necessary, existing structures can also be upgraded through targeted strengthening measures to support higher imposed loads. This may involve installing CFRP strips to increase flexural capacity or implementing additional shear reinforcement to improve punching shear resistance in flat slabs.
Particular attention must be paid to the development of suitable bracing systems, as existing components are often not designed to withstand additional horizontal loads.

Construction While Remaining Operational
Another key aspect is construction sequencing. Many extensions are carried out while operations continue – for example in industrial facilities, hospitals, or research buildings. We therefore plan the construction process to minimize disruption to ongoing operations.
Prefabrication can play a decisive role here. A structural system that can be assembled quickly and precisely on site reduces disruptions and shortens construction schedules.

Economic Efficiency
The high degree of uncertainty associated with existing structures makes effort and costs difficult to predict. Tight schedules and ongoing operations further increase complexity. At the same time, it is our responsibility as planners to advise clients openly and at an early stage – and, where necessary, to clearly state when building within existing structures is neither economically nor technically viable.
Unexpected challenges can significantly increase effort across all disciplines, often more than in a comparable new–build project.

Conclusion
Building within existing structures is far more than a technical adaptation of existing buildings. For structural engineering, it means analyzing existing systems and identifying their potential to enable new or modified uses. The challenge lies not only in structural performance, but also in the interaction of many factors: use, construction sequencing, expandability, and economic efficiency.
This is precisely why ATP is well prepared for building within existing structures – because we approach projects through integrated design and a holistic perspective from the very beginning. Across numerous projects, we have demonstrated how existing building fabric can be developed sustainably and how its lifecycle can be meaningfully extended.