Structural Engineers must change the collaborative process for designing a building and think about the materials they use in a different way. This begins at the very start of a potential project when the brief is being established.
Here are my thoughts on how to reshape that process to maximise reuse, circularity, and sustainability.
We know that we cannot keep demolishing our existing building stock and achieve the significant reductions in carbon and waste required of the construction industry.
There will be buildings which are genuinely at the end of their life or unsuitable for adaptation, however these should be viewed as the exceptions. The decision to demolish should only be made once the refurbishment opportunities have been investigated, as this is where big sustainability wins can be made.
If we consider an existing disused building on an urban site, the conventional approach would be to sketch out a vision for the site, which the design team ‘makes work’, either by justifying what is there for the new constraints and potentially significant alterations and enhancements, or by demolishing and starting afresh. But we should be advocating an alternative approach which optimises use of the existing asset and allows the brief to be shaped, where appropriate, around this.
The first step should be to research, model, and investigate the site and existing asset to explore what the opportunities are, and then create the brief.
This process is fundamental to getting the most out of existing structures and optimising the opportunity for retaining buildings or minimising demolition.
This may involve searching for archive information as a first step, which is possible to obtain for a remarkable array of building ages and types. This can be a real ‘game-changer’ when it can be found, as it gives a window into the original engineer or architect’s intentions, when the building was first created.
At HTS, we typically use this to create a 3D CAD model of the building. Then, investigations are carried out to verify the archive information and fill in the gaps, establishing a much more detailed picture of the existing structure.
The engineer can now evaluate the building and where opportunities for the architect and client can be highlighted.
Is there redundant capacity in the floors or foundations? What are the implications of adding floors, extending floorplates, infilling, or introducing lightwells? How much stability is there and how can we get the most out of the existing frame? All these, if communicated well, can inform the brief and how to undertake interventions in the most efficient way. And by working with these constraints and opportunities rather than against them, we can deliver a faster, cheaper, and significantly lower carbon building.
Alongside this, where elements of the building are to be demolished, it is worthwhile considering whether these can be deconstructed and reused instead. If any steelwork is relatively modern (post-1970s), in reasonable length sections and with simple connections, it could be ideal for reuse, either as part of the redevelopment or on another construction site through the reuse market. Carbon intensive foundations including piles can also be assessed for reuse.
Increasingly, other construction materials are being identified through pre-demolition audits and considered for reuse, but time needs to be built into the design programme to carry out this process and to be creative about the opportunities.
A client and design team can only make an educated and informed decision about options and design changes if all the data is clearly presented.
This is true of embodied carbon, and as a profession, we are becoming better at reporting carbon against design options at an early stage. There is still improvement to be made in keeping this ‘live’ throughout the design process, so that, as the design evolves, the team can see how the carbon is changing. Where it is rising, it should be identified as the changes are happening, providing the opportunity to address it in the design and reverse a negative trend. Or, if this is not possible, push to make efficiencies elsewhere to compensate.
This needs to be part of the conversation in presentations and meetings: not a small number quietly recorded in a report or drawing, but something fundamental to the design process and continually monitored and reported.
Finally, while designing for the lowest possible upfront embodied carbon now, we also need to remember that the most sustainable building is the one that is still being used in 100 years’ time. While considering this, we need to avoid falling into the trap of over-designing everything and beefing up the structure and embodied carbon, which we are simultaneously trying to make as lean as possible!
We can, however, make building as dismantle-able as possible, alongside looking at realistic scenarios of how the building may need to adapt for future uses, including increased height, new voids and lightwells or other changes. Where possible, these are incorporated into the design as future strengthening options rather than being an over-sizing of the base design – this can form a set of adaptions and strengthening details which sit alongside the base design ready for use in the future.
By understanding existing structures on a site and using this knowledge to inform the way the design develops in collaboration with the wider team, we structural engineers can inform the brief and design of the building in a positive way, which reduces upfront carbon and enhances reuse, circularity and long life.
Susan Mantle, Technical Director, Heyne Tillett Steel, will be speaking at the Design for the future, now e-conference on 29 – 30 March 2023.
Designing for the future, now – e-conference
Societal, technological, regulatory, and legislative drivers are encouraging unprecedented innovation in the construction industry. Join industry leaders and find out how your business can keep pace and adapt in this rapidly changing world.
About the author
Technical Director, Heyne Tillett Steel
Susan focuses in achieving the best structural solution for projects and relishes the creative nature of the design process. She has worked on a range of diverse and interesting projects, from private houses to large residential schemes, commercial buildings, museums, schools and theatres. Susan champions technical excellence across design and analysis and leads HTS+ Innovation and Research, a dedicated team who works on research projects to help resolve engineering challenges.