To decarbonize the built environment, we need to focus on reusing the world’s extensive stock of existing buildings. However, when it comes to tall buildings, retrofit, refurbishment and adaptive reuse can involve significant structural engineering challenges. In partnership with the Council on Tall Buildings and Urban Habitat (CTBUH) Engineering Technical Assembly, we brought industry experts together at this year’s CTBUH Conference to explore how we can better define, design and deliver projects. Here are some of the key takeaways.
 

1. Let the building tell you its potential to maximize the social, cultural and financial value of its reuse

Capturing robust data on every aspect of the existing building is essential – from its structure, façade and load paths to the materials used in its construction. These insights will enable as much of the building to be reused as possible, reducing embodied carbon emissions while preserving its unique identity. They will also determine where justifiable alterations can be made to optimize capacity and enhance spaces for a new generation of building users. Both aspects are equally important to lengthen a building’s original design life and make its reuse technically and commercially viable.

It’s important to explore the neighborhood and understand the building’s wider context and opportunities for placemaking. For example, the new public routes needed to improve access. A lot of work is needed at the start of a project to advise clients and define the brief – including the level of transformation needed for the most efficient, sustainable, future-proof retrofit, refurbishment or adaptive reuse. 

2. Assess as much as possible onsite and be prepared for the unknown

Surveying and testing upfront will help detail which elements of the building can be retained and what needs replacing. For example, the integrity of structural materials like concrete and steel and fire protection systems. Our engineers also assess the influence of the building’s past and current uses, design life, utilization and maintenance, alongside the impact of potential new uses, evolving building standards and adding extra capacity, such as a new extension or lifts.

However, even with access to the property and building records, it’s not possible to test everything. Existing buildings are often home to ‘known unknowns’ and ‘unknown unknowns’ only found once construction gets underway – from variations in the structure and materials, to previous alterations and extensions.

Close collaboration between designers and engineers can help projects validate onsite observations, test design assumptions and react quickly to changing design requirements. On a recent adaptive reuse project in London, our team discovered during construction that the historic front façade was a series of different steel frames. Together, we adapted the structural arrangement to retain the continuous street façade with a new commercial development inside.
 

3. Collaborate as clients, architects, engineers and contractors from the earliest stage

The decision-making process behind the reuse of an existing building can be as complex and multifaceted as the building itself. Working together from the start will enable everyone involved to understand the project’s challenges and drivers, including low carbon investment opportunities, planning requirements and client/tenant needs. It will also help create a compelling story about the project and its purpose for stakeholders including the local community – communicating how it will improve the building, the neighborhood and people’s lives.

Structural and MEP engineers are vital to assess the potential of a building, define the brief and optimize the design. For example, retrofitting exposed building services in a commercial reuse project could free up space, improve energy efficiency and reduce operational carbon emissions.
 

4. Embrace a dynamic design process driven by technology

In a building reuse project, each stage and discipline involved are interconnected and interdependent. For example, optimizing energy efficient MEP design relies on understanding the specific needs of building users. Technology is increasingly driving this dynamism. From data analysis enabling different design scenarios to be scientifically tested and compared including the impacts of wind, climate change and solar radiation, to early modelling analysis assessing the impact of potential alterations, such as adding floors to an existing building.

Buildings need to be flexible and resilient enough to change in the future – to adapt to the needs of new building users and the shifting landscape of planning and regulation. Technology is also helping project teams lengthen the life of existing buildings and allow for more optimizing in the future, by building in tolerances and extra spaces and creating robust building records including digital twins.